Overcharge-preventable secondary battery and charging method thereof

Abstract

The present invention relates to a secondary battery capable of preventing overcharging and a charging method thereof. The secondary battery includes a conductor part that electrically connects a positive electrode lead and a negative electrode lead, and a temperature-sensing part that changes shape under high temperature conditions is introduced into an end of the conductor part on the negative electrode lead side, and the voltage between the positive electrode lead and the negative electrode lead is measured during overcharging. This allows charging of the secondary battery to be immediately interrupted when the secondary battery is overcharged, thereby providing the advantage of further improving the safety of the battery.

Description

[Technical field]

[0001] The present invention relates to a secondary battery capable of preventing overcharging and a charging method thereof.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0149067 dated November 2, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference. [Background technology]

[0003] With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Among such secondary batteries, lithium secondary batteries, which have high energy density and high discharge voltage, are particularly widely used.

[0004] However, such lithium secondary batteries have a large safety disadvantage since they contain various flammable materials and may generate heat or explode due to overcharging, overcurrent, other physical external impacts, etc. That is, when a lithium secondary battery is exposed to high temperatures or a large current flows within a short period of time due to overcharging, an external short circuit, nail penetration, local crush, etc., the battery heats up due to IR heating, and there is a risk of fire / explosion.

[0005] Specifically, when the temperature of the battery rises, the reaction between the electrolyte and the electrodes is accelerated. As a result, reaction heat is generated, and the temperature of the battery rises further, which further accelerates the reaction between the electrolyte and the electrodes. Therefore, the temperature of the battery rises rapidly, which further accelerates the reaction between the electrolyte and the electrodes. This vicious cycle causes a thermal runaway phenomenon in which the temperature of the battery rises rapidly, and if the temperature rises above a certain level, the battery may catch fire. In addition, as a result of the reaction between the electrolyte and the electrodes, gas is generated, which increases the internal pressure of the battery, and if the pressure exceeds a certain level, the lithium secondary battery will explode. This risk of fire / explosion is a fatal disadvantage of lithium secondary batteries.

[0006] Therefore, ensuring safety is an essential consideration in the development of lithium secondary batteries. As part of efforts to ensure safety, there are two methods: attaching a safety element to the outside of the cell and using a substance inside the cell. The former includes PTC elements, CID elements, protection circuits that use changes in voltage, and safety vents that use changes in the battery's internal pressure, while the latter includes adding substances that can change physically, chemically, or electrochemically depending on changes in temperature or voltage inside the battery.

[0007] However, the technologies known so far each have their own problems. For example, the conventional safety element attached to the outside of the cell does not provide safety when the inside of the cell is already filled with flammable gas due to an abnormality in the battery, and the CID element has the disadvantage that it can only be applied to cylindrical batteries. In addition, it is known that it does not sufficiently perform the protective role when a fast response time is required, such as for internal short circuits, needle-like penetration, local damage, etc.

[0008] In addition, one method of using a substance inside the cell is to add an additive to the electrolyte or electrodes to improve safety. Chemical safety devices have the advantage that they do not require additional processes and space and can be applied to all types of batteries, but they have the problem that the performance of the battery is reduced by adding a substance. Such substances include substances that form a passivation film on the electrode and substances that expand in volume when the temperature rises and increase the resistance of the electrode. However, each of these has problems such as by-products being generated when the passivation film is formed, which reduces the performance of the battery, or the size of the substance occupying the inside of the battery is large, which reduces the capacity of the battery, and they are not used as a single means because they do not provide reliable safety assurance. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2016-200539 A Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, the present invention provides a secondary battery and a charging method thereof that improves safety issues caused by overcharging by detecting an overcharged state of the secondary battery and interrupting the charging current supplied to the secondary battery. [Means for solving the problem]

[0011] In order to achieve the above objectives, In one embodiment, the present invention comprises: an electrode assembly having a positive electrode lead and a negative electrode lead at both ends; A conductor portion, one end of which is electrically connected to the positive electrode lead; a voltage measuring unit electrically connected to a middle of the conductor unit; The conductive wire is inserted into one end opposite to the end electrically connected to the positive electrode lead, and provides a secondary battery including a temperature sensor that electrically connects the positive electrode lead and the negative electrode lead according to temperature conditions.

[0012] Here, the temperature sensing part is deformed when exposed to temperatures of 70° C. to 100° C., and can electrically connect the positive electrode lead and the negative electrode lead.

[0013] The temperature sensitive portion may also be made of a shape memory alloy including a nickel-titanium alloy, or may be made of a bimetal including a first metal made of a nickel-iron alloy and a second metal made of a nickel-manganese-iron alloy, a nickel-molybdenum-iron alloy, or a nickel-manganese-copper alloy.

[0014] Furthermore, when the conductive wire portion is connected to the negative lead due to deformation of the temperature sensing portion, the voltage measuring portion can measure the voltage between the positive lead and the negative lead.

[0015] The secondary battery may further include a controller electrically connected to the voltage measuring unit and receiving a voltage value measured by the voltage measuring unit.

[0016] The control unit can interrupt charging of the secondary battery if the voltage value transmitted from the voltage measuring unit is equal to or greater than a predetermined value.

[0017] In one embodiment, the present invention provides a method for producing a composition comprising: supplying power to the secondary battery according to the present invention to charge it; When a temperature sensing unit of a conductor unit provided in the secondary battery is electrically connected to a negative electrode lead, a voltage measuring unit measures a voltage; and stopping charging of the secondary battery if the measured voltage value is equal to or greater than a predetermined value.

[0018] At this time, the temperature sensing part is deformed when exposed to temperatures of 70° C. to 100° C., and can electrically connect the positive electrode lead and the negative electrode lead.

[0019] For this purpose, the temperature sensitive part may be made of a shape memory alloy including a nickel-titanium alloy, or may be made of a bimetal including a first metal made of a nickel-iron alloy and a second metal made of a nickel-manganese-iron alloy, a nickel-molybdenum-iron alloy, or a nickel-manganese-copper alloy. Effect of the Invention

[0020] The secondary battery according to the present invention includes a conductor part that electrically connects a positive electrode lead and a negative electrode lead, and a temperature-sensing part that changes shape under high temperature conditions is introduced into an end of the conductor part on the negative electrode lead side, and a configuration that measures the voltage between the positive electrode lead and the negative electrode lead during overcharging is configured so that charging can be immediately interrupted when the secondary battery is overcharged, thereby providing an advantage of further improving the safety of the battery. [Brief description of the drawings]

[0021] [Figure 1]1 is a top view illustrating a schematic configuration of a secondary battery according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a front view illustrating the secondary battery of FIG. [Diagram 3] 3 is a front view showing a state in which the shape memory alloy serving as the temperature sensitive portion in FIG. 2 is deformed and connected to a negative electrode lead. [Figure 4] FIG. 4 is a front view illustrating a schematic configuration of a secondary battery according to a second embodiment of the present invention. [Diagram 5] 5 is a front view showing a state in which the bimetal as the temperature sensing part in FIG. 4 is deformed and connected to a negative electrode lead. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The present invention can be modified in various ways and can have various embodiments, and a specific embodiment will be illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to the specific embodiment, and it should be understood that the present invention includes all modifications, equivalents, or alternatives within the spirit and technical scope of the present invention.

[0023] The terms used in the present invention are merely used to describe certain embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless the context clearly indicates otherwise. In the present invention, the terms "include" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0024] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. At this time, it should be noted that in the accompanying drawings, the same components are denoted by the same reference numerals as much as possible. Also, detailed descriptions of known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, some components are exaggerated, omitted, or illustrated in a schematic manner in the accompanying drawings.

[0025] <Secondary battery> In one embodiment, the present invention comprises: an electrode assembly having a positive electrode lead and a negative electrode lead at both ends; A conductor portion, one end of which is electrically connected to the positive electrode lead; a voltage measuring unit electrically connected to a middle of the conductor unit; The conductive wire portion is introduced into the other end opposite the one end electrically connected to the positive electrode lead, and a secondary battery including a temperature sensor electrically connecting the positive electrode lead and the negative electrode lead according to temperature conditions is provided.

[0026] The secondary battery according to the present invention includes an electrode assembly having a positive electrode lead and a negative electrode lead, and the electrode assembly may be composed of a positive electrode, a negative electrode, and a separator disposed between them inside a battery case. The electrode assembly is inserted into a pouch with the positive electrode and the negative electrode included in the electrode assembly connected to the positive electrode lead and the negative electrode lead, respectively. The positive electrode lead and the negative electrode lead are disposed to protrude outside the pouch, and the ends of the pouch may be sealed by thermocompression.

[0027] In this case, a type in which the positive electrode lead and the negative electrode lead are disposed at both ends of the electrode assembly is shown, but the present invention can also be applied to a type in which the positive electrode lead and the negative electrode lead are disposed at one end of the electrode assembly.

[0028] The electrode assembly includes a conductor portion having one end electrically connected to the positive electrode lead. The conductor portion is electrically connected to the positive electrode lead by removing the coating from an end of the conductor and welding the end of the conductor to the upper surface of the positive electrode lead. One end of the conductor portion may be bent so that the end is parallel to the upper surface of the positive electrode lead in order to increase the contact length with the upper surface of the positive electrode lead.

[0029] In addition, the conductor portion may be disposed at any position without any particular limitation as long as it can be disposed without inducing an internal short circuit between the positive electrode lead and the negative electrode lead of the electrode assembly. Specifically, the conductor portion may be positioned outside the pouch in which the electrode assembly is inserted, and may be electrically connected to the positive electrode lead and the negative electrode lead protruding outside the pouch, and in some cases, the surface of the conductor portion may be insulated coated so as not to induce an internal short circuit, and may be electrically connected to the positive electrode lead and the negative electrode lead inside the pouch in which the electrode assembly is inserted.

[0030] In addition, the conductor unit includes a temperature sensor that changes shape according to temperature conditions at the other end opposite to the end electrically connected to the positive electrode lead, and electrically connects to the negative electrode lead. That is, the shape of the temperature sensor changes in response to heat generated in the electrode assembly when the secondary battery is overcharged, thereby connecting the negative electrode lead of the secondary battery to the conductor.

[0031] The temperature-sensing part may deform when exposed to a high temperature condition, for example, a temperature of 70°C to 100°C, specifically, a temperature of 80°C to 100°C or 75°C to 95°C, in order to electrically connect the positive electrode lead and the negative electrode lead.

[0032] Such a temperature-sensing part is not particularly limited in type as long as it can change shape in a temperature range of 70°C to 100°C, but specifically may be composed of a shape memory alloy containing one or more of a nickel-titanium alloy and a copper-zinc-aluminum alloy; or the temperature-sensing part may be composed of a bimetal containing a first metal made of a nickel-iron alloy and a second metal made of a nickel-manganese-iron alloy, a nickel-molybdenum-iron alloy, or a nickel-manganese-copper alloy.

[0033] As an example, the temperature sensitive portion may include a nickel-titanium alloy having excellent shape recovery ability and workability.

[0034] As another example, the temperature sensitive portion may include a first metal made of a nickel-iron alloy and a second metal made of a nickel-manganese-iron alloy.

[0035] In addition, the voltage measuring unit is electrically connected to the middle of the conductor unit. That is, conductor connection terminals may be provided at both ends of the voltage measuring unit. When one end of the conductor unit is connected to the positive electrode lead and the other end is connected to the temperature sensor arranged to contact the upper surface of the electrode assembly, the voltage measuring unit may not be arranged on the electrode assembly but may be arranged at a position separated from the electrode assembly.

[0036] A secondary battery charging device generally includes a voltage measuring unit that measures the pressure between the positive and negative electrodes of an electrode assembly. Therefore, the secondary battery of the present invention can be constructed by connecting the positive electrode lead and the conductor connected to the temperature sensor to the voltage measuring unit.

[0037] In addition, the voltage measuring unit continues to measure the voltage during charging, and the measured voltage value becomes zero before the temperature sensing unit is connected to the negative lead. That is, the voltage measuring unit continues to operate during charging of the secondary battery, but heat is generated due to overcharging of the secondary battery, which causes the temperature sensing unit to deform, and the voltage between the positive and negative leads of the electrode assembly cannot be measured before the temperature sensing unit is connected to the negative lead, so that the voltage measuring unit can have a result value of zero. In addition, when the temperature sensing unit deforms under high temperature conditions and connects to the negative lead, the voltage measuring unit electrically connected to the middle of the conductor unit can measure the voltage between the positive and negative leads.

[0038] In addition, the voltage measuring unit may be electrically connected to the control unit and may transmit a measured voltage value to the control unit. The control unit may interrupt charging of the secondary battery when a voltage equal to or greater than a predetermined value is measured by the voltage measuring unit.

[0039] Specifically, when a power source is connected to the positive and negative leads of the electrode assembly and charging is performed, heat is generated in the electrode assembly. The temperature sensor is in contact with the upper surface of the electrode assembly and can transfer heat by conduction. When the temperature of the temperature sensor rises due to the transfer of heat, the end of the temperature sensor on the negative lead side, in particular, is thermally deformed and can be connected to the negative lead at a predetermined temperature or higher. When the temperature sensor connects to the negative lead, the voltage charged in the electrode assembly up to that point is measured. When the voltage measuring unit measures a predetermined voltage slightly greater than approximately zero, the control unit can interrupt charging of the secondary battery. This can prevent the secondary battery from swelling due to overcharging and catching fire.

[0040] Here, the above-mentioned predetermined voltage value is a preset value, and may be 4.0V or more, specifically, 4.1V or more, 4.2V or more, 4.2 to 4.8V, or 4.2 to 4.5V.

[0041] Meanwhile, the secondary battery may be a lead acid battery, a nickel-cadmium (NiCd) battery, a nickel-metal hydride (Ni-MH) battery, a lithium-ion (Li-ion) battery, or a lithium-ion polymer (Li-ion polymer) battery. As an example, the secondary battery may be a lithium-ion battery. Lithium-ion batteries are light, have a large capacity, have almost no self-discharge, and have a high voltage, and therefore occupy a large portion of the secondary battery market. However, lithium-ion batteries may swell and explode or catch fire when overcharged, so there is an even greater need for overcharge prevention, as in the present invention.

[0042] <How to charge a secondary battery> In one embodiment, the present invention provides a method for producing a composition comprising: Supplying power to the secondary battery according to the present invention to charge it; When a temperature sensing unit of a conductor unit provided in the secondary battery is electrically connected to a negative electrode lead, a voltage measuring unit measures a voltage; transmitting the measured voltage value to the control unit, and stopping charging of the secondary battery if the transmitted voltage value is equal to or greater than a predetermined value.

[0043] The method for charging a secondary battery according to the present invention is a method for charging the above-mentioned secondary battery of the present invention, in which power is supplied to the secondary battery of the present invention to charge it, and when the temperature sensing portion of the conductor portion provided in the secondary battery is deformed due to heat generated in the electrode assembly during overcharge and electrically connected to the negative electrode lead, the voltage measuring portion measures the voltage.

[0044] At this time, the temperature sensing part may deform when exposed to a high temperature condition, for example, a temperature of 70°C to 100°C, specifically, a temperature of 80°C to 100°C or 75°C to 95°C, in order to electrically connect the positive electrode lead and the negative electrode lead.

[0045] Such a temperature-sensing part is not particularly limited in type as long as it can change shape in a temperature range of 70°C to 100°C, but specifically may be composed of a shape memory alloy containing one or more of a nickel-titanium alloy and a copper-zinc-aluminum alloy; or the temperature-sensing part may be composed of a bimetal containing a first metal made of a nickel-iron alloy and a second metal made of a nickel-manganese-iron alloy, a nickel-molybdenum-iron alloy, or a nickel-manganese-copper alloy.

[0046] As an example, the temperature sensitive portion may include a nickel-titanium alloy having excellent shape recovery ability and workability.

[0047] As another example, the temperature sensitive portion may include a first metal made of a nickel-iron alloy and a second metal made of a nickel-manganese-iron alloy.

[0048] In addition, when the voltage measuring unit measures the voltage, it can transmit the measured voltage value to the control unit as a voltage signal, and the control unit can interrupt charging of the secondary battery if the transmitted voltage value is equal to or greater than a predetermined value.

[0049] Here, the above-mentioned predetermined voltage value is a preset value, and may be 4.0V or more, specifically, 4.1V or more, 4.2V or more, 4.2 to 4.8V, or 4.2 to 4.5V.

[0050] The secondary battery may be a lead acid battery, a nickel-cadmium (NiCd) battery, a nickel-metal hydride (Ni-MH) battery, a lithium-ion (Li-ion) battery, or a lithium-ion polymer (Li-ion polymer) battery. As an example, the secondary battery may be a lithium-ion battery. Lithium-ion batteries are light, have a large capacity, have almost no self-discharge, and have a high voltage, and therefore occupy a large portion of the secondary battery market. However, lithium-ion batteries may swell and explode or catch fire when overcharged, so there is an even greater need for overcharge prevention as in the present invention.

[0051] Hereinafter, various embodiments of a secondary battery and a method for charging the secondary battery according to the present invention will be described with reference to the accompanying drawings.

[0052] (First embodiment) FIG. 1 is a top view showing the schematic configuration of a secondary battery according to a first embodiment of the present invention, FIG. 2 is a front view showing the secondary battery of FIG. 1, and FIG. 3 is a front view showing the state in which a shape memory alloy as a temperature sensing part of FIG. 2 has been deformed and connected to a negative electrode lead.

[0053] The secondary battery 100 according to the first embodiment of the present invention includes an electrode assembly 110 having a positive electrode lead 120 and a negative electrode lead 130 at both ends, a conductor portion 140 having one end electrically connected to the positive electrode lead, a temperature sensing portion 150 electrically connected to the other end opposite the one end of the conductor portion electrically connected to the positive electrode lead and at least a portion of which contacts the electrode assembly 110, a voltage measuring portion 160 electrically connected to the middle of the conductor portion, and a control portion 190 which interrupts charging of the electrode assembly 110 when the temperature sensing portion 150, which includes a shape memory alloy, deforms and connects to the negative electrode lead 130, thereby connecting the temperature sensing portion 150 to the negative electrode lead 130, and the voltage measured by the voltage measuring portion 160 is equal to or greater than a predetermined value.

[0054] Here, the positive electrode lead 120 and the negative electrode lead 130 are disposed at both ends of the electrode assembly 110, and the conductor portion 140 is electrically connected to the positive electrode lead 120, and may be connected by removing the coating at the end of the conductor and welding the end of the conductor to the upper surface of the positive electrode lead 120. One end of the conductor portion 140 may be bent so that the end is parallel to the upper surface of the positive electrode lead 120 in order to increase the contact length with the upper surface of the positive electrode lead 120.

[0055] The temperature sensing unit 150 may be electrically connected to the other end of the conductive wire unit 140. The temperature sensing unit 150 may be made of a conductive metal that not only deforms depending on temperature but also connects to the other end of the conductive wire unit 140 and through which a current flows. The temperature sensing unit 150 is a part that deforms when it receives heat transferred from the electrode assembly 110, and most of the temperature sensing unit 150, except for a part on the negative electrode lead 130 side, may be disposed so as to contact the upper surface of the electrode assembly 110.

[0056] The voltage measuring unit 160 is electrically connected to the middle of the conductor unit 140. That is, conductor connection terminals may be provided at both ends of the voltage measuring unit 160. When one end of the conductor unit 140 is connected to the positive electrode lead 120 and the other end is connected to the temperature sensing unit 150 arranged to contact the upper surface of the electrode assembly 110, the voltage measuring unit 160 may be arranged at a position separated from the electrode assembly 110 rather than being arranged on the electrode assembly 110.

[0057] The control unit 190 may interrupt charging of the electrode assembly 110 when the voltage measuring unit 160 measures a voltage equal to or greater than a predetermined value. When charging is performed by connecting a power source to the positive electrode lead 120 and the negative electrode lead 130 of the electrode assembly 110, heat is generated from the electrode assembly 110. The temperature sensing unit 150 is in contact with an upper surface of the electrode assembly 110, and thus may transfer heat by conduction. When the temperature of the temperature sensing unit 150 increases due to the transfer of heat, the end of the temperature sensing unit 150, particularly the end on the negative electrode lead 130 side, may thermally deform and may connect to the negative electrode lead 130 at a temperature equal to or greater than a predetermined temperature.

[0058] In addition, the voltage measuring unit 160 continues to measure the voltage during charging, and the measured voltage value becomes zero before the temperature sensing unit 150 including the shape memory alloy is connected to the negative electrode lead 130. Thereafter, when the temperature sensing unit 150 is connected to the negative electrode lead 130, the voltage charged in the electrode assembly 110 up to that point is measured. The control unit 190 can interrupt the charging of the electrode assembly 110 when the voltage measuring unit 160 measures a predetermined voltage value slightly greater than approximately zero, for example, 4.2 to 4.5 V or 4.2 to 4.3 V. This can prevent a swelling phenomenon in which the secondary battery swells due to overcharging, or a fire.

[0059] Meanwhile, the temperature sensing unit 150 receives heat from the electrode assembly 110, and is deformed at a temperature of 80 to 100° C., and can be connected to the negative electrode lead 130. Even if the temperature sensing unit 150 is deformed at a temperature between room temperature and less than 80° C., it does not connect to the negative electrode lead 130, but when it reaches any one of temperatures between 80 and 100° C., the temperature sensing unit 150 is deformed and starts to connect to the negative electrode lead 130.

[0060] A shape memory alloy is an alloy that has the property of returning to its original shape when heated even if it is deformed into another shape. The temperature sensing part 150 can be manufactured by pressing the original shape as shown in Fig. 3 into a substantially rectangular plate shape at room temperature. When the temperature sensing part 150 is heated to 80 to 100°C, it deforms to its original curved shape, and the temperature sensing part 150 can be connected to the negative electrode lead 130.

[0061] The temperature sensing part 150 may be made of a nickel-titanium alloy. Representative shape memory alloys include nickel-titanium alloy and copper-zinc-aluminum alloy. Although nickel-titanium alloy has the disadvantage of being expensive as nickel and titanium, it has excellent shape recovery ability and processability and is more preferable than copper-zinc-aluminum alloy.

[0062] In the present specification, it has been described that the conductive portion 140 is connected to the positive electrode lead 120 and the temperature sensing portion 150 is deformed and connected to the negative electrode lead 130, but the conductive portion 140 may be configured to be connected to the negative electrode lead 130 and the temperature sensing portion 150 is deformed and connected to the positive electrode lead 120.

[0063] According to the secondary battery according to the first embodiment of the present invention, when the voltage is measured using the temperature sensor and the voltage measuring unit, charging is interrupted, thereby making it possible to prevent overcharging in advance.

[0064] Second embodiment FIG. 4 is a front view showing a schematic configuration of a secondary battery according to a second embodiment of the present invention, and FIG. 5 is a front view showing a state in which a temperature sensing part including a bimetal of FIG. 4 is deformed and connected to a negative electrode lead.

[0065] The secondary battery according to the second embodiment of the present invention includes an electrode assembly 110 having a positive electrode lead 120 and a negative electrode lead 130 at both ends thereof, a conductor unit 140 electrically connected to the positive electrode lead, a temperature sensor 170 electrically connected to the other end of the conductor unit opposite to the one end electrically connected to the positive electrode lead, and at least a portion of the temperature sensor 170 contacting the electrode assembly, a voltage measuring unit 160 electrically connected to the middle of the conductor unit, and a control unit 190 which interrupts charging of the electrode assembly 110 when the temperature sensor 170 including a bimetal deforms and connects to the negative electrode lead 130, and a voltage measured by the voltage measuring unit 160 is equal to or greater than a predetermined value.

[0066] The secondary battery of the second embodiment differs from the first embodiment in that the temperature sensing unit 170 includes a bimetal instead of a shape memory alloy part. Therefore, the following description will focus on the configuration of the temperature sensing unit 170 including the bimetal.

[0067] The temperature sensing unit 170 may be electrically connected to one end of the conductive wire unit 140, one end of which is connected to the positive electrode lead 120. The temperature sensing unit 170 may be deformed by heat transferred from the electrode assembly 110 when the electrode assembly 110 is charged, and may be connected to the negative electrode lead 130. The temperature sensing unit 170 may be disposed such that at least a portion thereof is in contact with the electrode assembly 110 so that heat can be transferred from the electrode assembly 110 by conduction.

[0068] Bimetal is made by stacking and welding two different thin metal plates together to form a single band. Since each metal has a different coefficient of thermal expansion, the length at which they expand varies with temperature changes, causing them to bend to one side.

[0069] The temperature sensing unit 170 including such a bimetal may receive heat from the electrode assembly 110, deform at a temperature of 80 to 100°C, and connect to the negative electrode lead 130. The temperature sensing unit 170 may be manufactured to deform at a temperature of 80 to 100°C according to the thermal expansion coefficients and shapes of the two metal materials, and connect to the negative electrode lead 130. A temperature of 80 to 100°C may be regarded as the temperature immediately before being overcharged in lithium ion batteries among secondary batteries.

[0070] For example, the temperature sensing unit 170 may include a first metal 172 made of a nickel-iron alloy, and a second metal 174 made of a nickel-manganese-iron alloy, a nickel-molybdenum-iron alloy, or a nickel-manganese-copper alloy. Here, the first metal 172 is a metal having a smaller thermal expansion coefficient than the second metal 174, and may be formed of an alloy containing nickel and iron. In addition, the second metal 174 is a metal having a larger thermal expansion coefficient than the first metal 172, and may be formed of a nickel-manganese-iron alloy, a nickel-molybdenum-iron alloy, or a nickel-manganese-copper alloy.

[0071] 3 and 4, the temperature sensing unit 170 is shown disposed on the upper surface of the electrode assembly 110, but the temperature sensing unit 170 including a bimetal may be disposed so as to be in contact with the lower surface of the electrode assembly 110. Since the second metal 174 is a metal having a larger thermal expansion coefficient than the first metal 172, it is more efficient for the second metal 174 to be in contact with the electrode assembly 110 and to directly transfer heat.

[0072] Third embodiment Next, a method for controlling charging of a secondary battery according to the present invention will be described with reference to the drawings.

[0073] First, a power source is connected to the positive electrode lead 120 and the negative electrode lead 130 of the electrode assembly 110 to supply power and perform charging.

[0074] Next, the voltage is measured by a voltage measuring unit 160 connected to the middle of a conductor part having one end connected to the positive electrode lead 120 and the other end connected to the temperature sensor 150 or 170 .

[0075] In this case, the temperature sensing unit 150 or 170 may include the shape memory alloy of the first embodiment or the bimetal of the second embodiment. The temperature sensing unit 150 including the shape memory alloy can be connected to the negative electrode lead 130 by contacting at least a portion of the electrode assembly 110 and being deformed by receiving heat transfer from the electrode assembly. The temperature sensing unit 170 including the bimetal can be connected to the negative electrode lead 130 by contacting at least a portion of the electrode assembly 110 and being deformed by receiving heat transfer from the electrode assembly.

[0076] In addition, the voltage measuring unit 160 can continue to measure the voltage after charging starts and transmit a voltage signal to the control unit 190.

[0077] Finally, when the temperature sensing unit 150 or 170 is deformed and connected to the negative electrode lead 130, the charging of the electrode assembly 110 is stopped if the voltage measured by the voltage measuring unit 160 is equal to or greater than a predetermined value.

[0078] Specifically, the temperature sensing unit 150 or 170 is deformed by heat transferred from the electrode assembly 110 during charging of the electrode assembly 110, and then, when the temperature reaches 80 to 100° C., it can be connected to the negative electrode lead 130. As a result, the voltage value measured by the voltage measuring unit 160 increases from zero to a predetermined value or more, and the control unit 190 can interrupt charging of the electrode assembly 110 when this voltage signal is received.

[0079] Although one embodiment of the present invention has been described above, a person having ordinary knowledge in the art may modify and change the present invention in various ways by adding, changing, deleting or adding components within the scope of the concept of the present invention described in the claims, and this also falls within the scope of the present invention. [Explanation of symbols]

[0080] 100 Secondary battery 110 Electrode assembly 120 Positive lead 130 Negative lead 140 Conductor section 150 Temperature sensor 160 Voltage measurement section 170 Temperature sensor 172 First metal 174 Second metal 190 Control section

Claims

1. an electrode assembly having a positive electrode lead and a negative electrode lead at both ends; a conductor portion having one end electrically connected to the positive electrode lead; a voltage measuring unit electrically connected to a middle of the conductor unit, The conductive wire portion is introduced into the other end opposite the one end electrically connected to the positive electrode lead, contacts the electrode assembly, and electrically connects the positive electrode lead and the negative electrode lead when heat generated in the electrode assembly is transferred thereto and a temperature rises.

2. The secondary battery of claim 1, wherein the temperature sensing part is deformed when exposed to a temperature of 70° C. to 100° C., and electrically connects the positive electrode lead and the negative electrode lead.

3. The secondary battery according to claim 1 , wherein the temperature sensitive portion is made of a shape memory alloy including a nickel-titanium alloy.

4. 2. The secondary battery according to claim 1, wherein the temperature sensitive portion is composed of a bimetal including a first metal made of a nickel-iron alloy and a second metal made of a nickel-manganese-iron alloy, a nickel-molybdenum-iron alloy, or a nickel-manganese-copper alloy.

5. The secondary battery according to claim 1 , wherein the voltage measuring unit measures a voltage between the positive electrode lead and the negative electrode lead when the conductive wire unit is connected to the negative electrode lead due to deformation of the temperature sensing unit.

6. The secondary battery of claim 1 , further comprising: a control unit electrically connected to the voltage measuring unit and receiving a voltage value measured by the voltage measuring unit.

7. The secondary battery according to claim 6 , wherein the control unit interrupts charging of the secondary battery when the voltage value transmitted from the voltage measurement unit is equal to or greater than a predetermined value.

8. A method for charging the secondary battery according to claim 1 by supplying power thereto; measuring a voltage by the voltage measuring unit when the temperature sensing unit of the conductor unit provided in the secondary battery is electrically connected to the negative electrode lead; and stopping charging of the secondary battery if the measured voltage value is equal to or greater than a predetermined value.

9. 9. The method of claim 8, wherein the temperature sensing part is deformed when exposed to a temperature of 70° C. to 100° C., and electrically connects the positive electrode lead and the negative electrode lead.

10. The method for charging a secondary battery according to claim 8 , wherein the temperature sensitive portion is made of a shape memory alloy including a nickel-titanium alloy.

11. 9. The method for charging a secondary battery according to claim 8, wherein the temperature sensing portion is composed of a bimetal including a first metal made of a nickel-iron alloy and a second metal made of a nickel-manganese-iron alloy, a nickel-molybdenum-iron alloy, or a nickel-manganese-copper alloy.

Images