Patent Description:
The present invention relates to a gas detection apparatus for cell module assemblies capable of accurately and rapidly detecting a cell having a damaged battery cell module assembly and a damaged position of the cell and a gas detection method for cell module assemblies using the same.

Secondary batteries, which have high applicability and electrical properties, such as high energy density, have generally been used in electric vehicles (EV) or hybrid electric vehicles (HEV), each of which is driven using an electrical driving source, as well as portable devices. Such secondary batteries have attracted attention as a new energy source capable of increasing environmental friendliness and energy efficiency, since no by-products are generated as the result of use of energy in addition to a primary advantage in that it is possible to remarkably reduce the use of fossil fuels.

There are a lithium ion battery, a lithium polymer battery, a nickel-cadmium battery, a nickel-hydride battery, and a nickel-zinc battery as secondary batteries that are widely used at present. The operating voltage of a unit secondary battery cell, i.e. a unit battery cell, is about <NUM>. 5V to <NUM>. In the case in which output voltage higher than the above operating voltage is required, therefore, a plurality of battery cells may be connected to each other in series to constitute a battery pack. In addition, a plurality of battery cells may be connected to each other in parallel depending on required charge and discharge capacities of a battery pack in order to constitute the battery pack. Consequently, the number of battery cells included in the battery pack may be variously set depending on required output voltage or charge and discharge capacities.

Meanwhile, in the case in which a plurality of battery cells is connected to each other in series/parallel to constitute a battery pack, a battery module including a plurality of battery cells may be manufactured first, and a battery pack may be manufactured using a plurality of battery modules and other components, which is a general method.

Meanwhile, in the case in which a battery cell assembly is constituted by a plurality of battery cells in the battery module, each of the battery cells may be a lithium polymer secondary battery cell.

In general, the lithium secondary battery is classified as a liquid electrolyte battery or a polymer electrolyte battery based on the kind of an electrolytic solution. A battery using a liquid electrolyte is called a lithium ion battery, and a battery using a polymer electrolyte is called a lithium polymer battery. In addition, various kinds of sheathing members may be used for the lithium secondary battery. Typically, a cylindrical sheathing member, a prismatic sheathing member, and a pouch sheathing member are used. An electrode assembly configured to have a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed therebetween are stacked or wound is provided in the sheathing member of the lithium secondary battery.

Conventionally, in a device, such as a vehicle, to which a battery module including a plurality of stacked electrode assemblies is applied, an electrolytic solution leaks from a cell constituting each electrode assembly due to damage to a case thereof caused by external influence during a manufacturing/assembly process thereof, or toxic gases generated due to electrochemical reaction between an electrode, an active material, and an electrolytic solution is introduced into the vehicle.

In the case in which the electrolytic solution leaks from the battery due to damage to or poor airtightness of the case, the product is determined to be defective. For this reason, leakage inspection is performed on a manufacturing process line. In general, inspection is performed using a method of checking a welded portion of a cap plate welded to the case using X-rays or with the naked eye.

However, X-ray inspection is less practicable since a process and equipment are complicated, and visual inspection has low reliability.

In order to solve the above problems, <CIT> discloses a method of capturing gas inside and outside a cell using a plurality of gas capturing tubes configured to capture gas to determine whether gas in the cell is discharged from the outside, and <CIT> discloses an apparatus that inspects a sealed state of a secondary battery using a vacuum chamber.

However, these methods, each of which inspects whether a case is defective for a unit cell constituting a battery module, have a disadvantage in that it is difficult to accurately sort a battery cell having defects, such as tear or cracks, from battery cells modularized by stacking in a process of manufacturing a battery cell module assembly.

Therefore, there is a high necessity for technology capable of accurately and rapidly sorting battery cells having defective cases during a battery cell module assembly manufacturing process before delivery of final products.

Further prior art is described in <CIT> and <CIT>.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a gas detection apparatus for cell module assemblies constituted by stacked battery cells and capable of accurately and rapidly detecting a cell having a damaged case of a battery cell module assembly and the damaged position of the cell having the damaged case. It is another object of the present invention to provide a gas detection method for cell module assemblies using the gas detection apparatus for cell module assemblies.

In order to accomplish the above objects, the present invention provides a gas detection apparatus (<NUM>) comprising the features of patent claim <NUM>, and a method of gas detection for battery cell module assemblies with the features of claim <NUM>.

Dependent claims are directed on features of preferred embodiments of the invention.

According to the present invention, it is possible to accurately and rapidly detect a defective battery cell among battery cells constituting a cell module assembly, and the defective position of the battery cell.

In addition, according to the present invention, it is possible to sort and replace defective cells in a cell module assembly production process, whereby it is possible to reduce a cell module assembly defect rate.

In the present application, it should be understood that the terms "comprises," "has," "disposes," "includes," etc. specify the presence of stated features, numbers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations thereof.

Hereinafter, the present invention will be described with reference to the accompanying drawings in order to assist in understanding the present invention.

<FIG> is a front view of a gas detection apparatus for cell module assemblies according to an embodiment of the present invention, and <FIG> is a perspective view of the gas detection apparatus for cell module assemblies according to the embodiment of the present invention.

Referring to <FIG> and <FIG>, the gas detection apparatus <NUM> for cell module assemblies includes a gas detection chamber unit <NUM>, a sliding die unit <NUM>, a gas sensor unit <NUM>, a gas circulation unit <NUM>, and a pressing unit <NUM>. In addition, the sliding die unit <NUM> according to the embodiment of the present invention includes a mounting die <NUM> and a sliding frame <NUM>, the gas sensor unit <NUM> includes a gas sensing portion <NUM> and a gas electrode portion <NUM>, and the gas circulation unit <NUM> includes an air suction device <NUM>, an air fan <NUM>, and an air blower <NUM>.

<FIG> is a perspective view of the gas detection chamber unit of the gas detection apparatus for cell module assemblies according to the embodiment of the present invention.

Referring to <FIG>, the gas sensor unit <NUM> is constituted by a plurality of gas sensors 130a and 130b provided at an outer wall of the gas detection chamber unit <NUM>, and each of the plurality of gas sensors <NUM> may be a semiconductor type gas sensor. The gas sensing portion <NUM> is a portion that directly reacts with gas that leaks due to damage to a cell according to the present invention to indicate a change in resistance, and the gas electrode portion <NUM> is a portion that transmits an electrical signal from the gas sensing portion <NUM> to the outside. Each of the gas sensors <NUM> is disposed at a corresponding one of cells constituting a cell module assembly <NUM>, or is disposed at a corresponding one of predetermined positions of the cells. The gas sensing portion <NUM> extends through the side wall of the gas detection chamber unit <NUM> such that one end of the gas sensing portion is disposed at the inner surface of the side wall of the gas detection chamber unit <NUM> so as to face an inner space of the gas detection chamber unit <NUM>, and the other end of the gas sensing portion <NUM> is connected to the gas electrode portion <NUM>. The gas sensing portion is connected to an external data logger (not shown), which realizes the kind and concentration value of a detected gas from the electrical signal from the gas sensing portion <NUM>. The plurality of gas sensors <NUM> are disposed respectively at the stacked cells of the cell module assembly <NUM> and at the predetermined positions of the cells so as to be spaced apart from each other by a predetermined distance, and the number of gas sensors is not particularly restricted. In addition, the plurality of gas sensors may be disposed respectively at outer surfaces of cases of the cells that face the outer wall of the gas detection chamber unit, or may be disposed respectively at the predetermined positions of the outer surfaces of the cases of the cells that face the outer wall of the gas detection chamber unit. Consequently, the gas sensors <NUM> are disposed at the cells included in the cell module assembly <NUM> or are disposed at the predetermined positions of the cells, whereby it is possible to check a cell having a damaged case, from among the cells of the cell module assembly, and/or the damaged position of the cell having the damaged case based on a detection result. In the cell module assembly production stage, therefore, it is possible to check a defect of a cell due to damage thereto in advance and to replace the damaged cell, whereby it is possible to reduce a cell module assembly defect rate.

The gas circulation unit <NUM> may include at least one selected from the group consisting of an air suction device <NUM>, an air fan <NUM>, and an air blower <NUM>. However, the present invention is not limited thereto. The air suction device <NUM> may be constituted by a duct provided so as to extend through an upper wall surface of the gas detection chamber unit <NUM> and a suction pump (not shown) connected to the other end of the duct, and suctions air in the gas detection chamber unit <NUM> through driving of the suction pump. Preferably, one or more air suction devices <NUM> are provided. One or more air fans <NUM> may be provided in the gas detection chamber unit <NUM>. Preferably, the air fan <NUM> may be disposed in a space defined between an inner upper end surface of the upper wall surface of the gas detection chamber unit <NUM> and an upper end surface of the cell module assembly received in the gas detection chamber unit <NUM>, and one or more air fans <NUM> may be provided. The air blower <NUM> may be constituted by a nozzle (not shown) extending through the wall surface of the gas detection chamber unit <NUM> and an air hose (not shown) coupled to the nozzle. The air blower <NUM> may be disposed so as to extend through the upper wall surface or a side wall surface of the gas detection chamber unit <NUM>. Preferably, the air blower is disposed spaced apart from the side wall surface of the gas detection chamber unit by a predetermined distance. One or more air blowers may be disposed depending on characteristics of the cell module assembly and other environments, and the number of air blowers is not particularly restricted.

<FIG> is a view showing the internal structure of the gas detection chamber unit according to the embodiment of the present invention.

Referring to <FIG>, the air suction device <NUM> is disposed so as to extend through the upper wall surface of the gas detection chamber unit <NUM>, a central shaft <NUM> connected to a motor <NUM> disposed at an upper end wall of the gas detection chamber unit <NUM> is disposed so as to extend through a central plate <NUM>, and the pressing unit <NUM> is coupled to an end of the central shaft <NUM> while being located at a lower end surface of the central plate <NUM>. A receiving space <NUM> configured to receive the cell module assembly is formed under the lower end of the pressing unit <NUM>. In addition, the pressing unit <NUM> presses the upper end surface of the cell module assembly while pressing pressure thereof is adjusted using a method of controlling the lowering height of the pressing unit by driving of the motor <NUM>.

<FIG> is a front view showing the state in which a cell module assembly according to an embodiment of the present invention is disposed at the lower end of the gas detection chamber unit.

Referring to <FIG>, when the mounting die <NUM> disposed at the upper end of the cell module assembly <NUM> is located at the lower end of the gas detection chamber unit <NUM> along the sliding frame <NUM>, the gas detection chamber unit <NUM> is moved downwards by downward operation of the stripper <NUM> mechanically coupled to the gas detection chamber unit <NUM>, whereby the lower end surface of the side wall of the gas detection chamber unit <NUM> comes into tight contact with the upper surface of the mounting die <NUM> while the cell module assembly <NUM> is received in the receiving space in the gas detection chamber unit <NUM>. Each of the gas detection chamber unit <NUM> and the mounting die <NUM> is provided with a fastening member (not shown), by which the inner space of the gas detection chamber unit <NUM> may be completely sealed. In addition, when gas detection is completed, the gas detection chamber unit <NUM> is moved upwards by upward operation of the stripper <NUM>, whereby the cell module assembly <NUM> and the sliding die unit <NUM> are opened, and the sliding die unit <NUM> is moved to replace the cell module assembly with another cell module assembly to be inspected.

<FIG> is a perspective view of a cell module assembly having cracks formed therein according to an embodiment of the present invention.

Referring to <FIG>, battery cells are stacked such that relatively wide surfaces of the battery cells face each other to constitute a cell module assembly, cracks p are formed in side surfaces of cases of the stacked battery cells <NUM> and in the upper surface of the uppermost battery cell that does not face the other battery cells or the lower part of the uppermost battery cell. The cracks may be distributed at various positions of the battery cells.

<FIG> is a photograph showing formation of a crack according to an embodiment of the present invention.

Referring to <FIG>, a circular-hole-shaped crack is formed in the surface of the case of one of the stacked cells constituting the cell module assembly. The diameter of the crack is <NUM>.

<FIG> is a flowchart of a gas detection method for cell module assemblies according to an embodiment of the present invention.

Referring to <FIG>, a method of detecting gas in a cell module assembly <NUM> using the gas detection apparatus for cell module assemblies includes a step of disposing the cell module assembly <NUM> at the upper end of the mounting die <NUM> of the sliding die unit <NUM> and transferring the cell module assembly <NUM> using the sliding die unit <NUM> such that the mounting die <NUM> is located at the lower end of the gas detection chamber unit <NUM> along the sliding frame <NUM>; a step of moving the gas detection chamber unit <NUM> downwards through downward operation of the stripper <NUM> such that the lower surface of the gas detection chamber unit <NUM> comes into tight contact with the upper surface of the mounting die <NUM> in order to receive the cell module assembly <NUM> mounted at the upper part of the mounting die <NUM> in the gas detection chamber unit <NUM>; a step of driving the gas circulation unit <NUM> to circulate gas in the gas detection chamber unit <NUM>; a step of detecting the gas in the gas detection chamber unit <NUM> using the gas sensor unit <NUM>; a step of moving the gas detection chamber unit <NUM> upwards through upward operation of the stripper <NUM> to separate the cell module assembly <NUM> and the sliding die unit <NUM> from the gas detection chamber unit; and a step of purifying the interior of the gas detection chamber unit <NUM> using the gas circulation unit <NUM>.

Also, in the step of receiving the cell module assembly in the gas detection chamber unit <NUM>, the lowering height of the stripper <NUM> may be adjusted, and the cell module assembly <NUM> may be pressed using the pressing unit <NUM>.

<FIG> show results of gas detection experiments on the cell module assembly according to examples of the present invention.

In the following examples of the present invention, the cell module assembly was disposed in the gas detection chamber unit <NUM> such that relatively long ones of the side surfaces of the stacked battery cells, excluding the stacked surfaces thereof, face the front wall surface and the rear wall surface of the gas detection chamber unit <NUM> and relatively short ones of the side surfaces of the stacked battery cells face the side wall surface of the gas detection chamber unit <NUM>. In addition, a CO<NUM> detection sensor was used as the gas sensor.

Cracks were formed at positions p3 and p6 of the cell module assembly <NUM> shown in <FIG>, and gas detection experiments were performed.

The cell module assembly <NUM> having cracks formed at positions p3 and p6 was disposed on the mounting die <NUM>, the mounting die <NUM> was moved along the sliding frame <NUM> so as to be located at the lower end of the gas detection chamber unit <NUM>, the stripper <NUM> was driven downwards such that the lower surface of the gas detection chamber unit <NUM> came into close contact with the upper surface of the mounting die <NUM>, gas in the gas detection chamber unit <NUM> was detected using the gas sensor unit <NUM> while the gas circulation unit <NUM> was driven to circulate the gas in the gas detection chamber unit <NUM>, result values were transmitted to the external data logger, and detected CO<NUM> concentration values were collected.

Experiment times and CO<NUM> concentration detection values according to Example <NUM> are shown in <FIG>.

Gas detection experiments were performed in the state in which the interior of the gas detection chamber unit <NUM> was completely sealed.

Gas detection experiments were performed in the same manner as in Example <NUM> except that the lower surface of the gas detection chamber unit <NUM> and the upper surface of the mounting die <NUM> were fastened to each other via a fastening member such that the interior of the gas detection chamber unit was completely sealed.

Gas detection experiments were performed in the state in which the cell module assembly <NUM> was not pressed in the gas detection chamber unit <NUM> that was partially sealed.

Cracks were formed at positions p1 and p4 of the cell module assembly <NUM> shown in <FIG>, and gas detection experiments were performed.

The cell module assembly <NUM> having cracks formed at positions p1 and p4 was disposed on the mounting die <NUM>, the mounting die <NUM> was moved along the sliding frame <NUM> so as to be located at the lower end of the gas detection chamber unit <NUM>, the stripper <NUM> was driven downwards such that the lower surface of the gas detection chamber unit <NUM> came into close contact with the upper surface of the mounting die <NUM>, gas in the gas detection chamber unit <NUM> was detected using the gas sensor unit <NUM> while the gas circulation unit <NUM> was driven to circulate the gas in the gas detection chamber unit <NUM>, result values were transmitted to the external data logger, and detected CO<NUM> concentration values were collected.

Gas detection experiments were performed in the state in which the cell module assembly <NUM> was pressed in the gas detection chamber unit <NUM> that was partially sealed.

Gas detection experiments were performed in the same manner as in Example <NUM> except that a step of bringing the lower surface of the gas detection chamber unit <NUM> into close contact the upper surface of the mounting die <NUM> and further driving the stripper <NUM> downwards in the state in which the pressing unit <NUM> was disposed in contact with the upper end surface of the cell module assembly <NUM> in order to press the upper end surface of the cell module assembly <NUM> was added.

Experiments on a gas circulation effect depending on change in operation conditions of the gas circulation unit <NUM> were performed in the state in which the interior of the gas detection chamber unit <NUM> was partially sealed and the cell module assembly <NUM> was not pressed.

The cell module assembly <NUM> having cracks formed therein was disposed on the mounting die <NUM>, the mounting die <NUM> was moved along the sliding frame <NUM> so as to be located at the lower end of the gas detection chamber unit <NUM>, the stripper <NUM> was driven downwards such that the lower surface of the gas detection chamber unit <NUM> came into close contact with the upper surface of the mounting die <NUM>, gas in the gas detection chamber unit <NUM> was detected using the gas sensor unit <NUM>, and result values were transmitted to the external data logger. In the step of detecting the gas using the gas sensor unit, the air fan <NUM> and the air blower <NUM> were individually or simultaneously driven either for <NUM> seconds or continuously to perform gas detection experiments.

Experiments on an effect of purifying the gas detection chamber unit <NUM> depending on change in operation conditions of the gas circulation unit <NUM> were performed in the state in which the interior of the gas detection chamber unit <NUM> was partially sealed and the cell module assembly <NUM> was not pressed.

Gas detection experiments according to the present invention were performed using the cell module assembly <NUM> having cracks formed in the surfaces of pouch cases of cells, and experiments to purify the gas detection chamber unit <NUM> through driving of the gas circulation unit <NUM> were performed after gas detection.

It can be seen from the experiment results that the gas detection chamber unit was the most quickly purified when the air suction device <NUM>, the air fan <NUM>, and the air blower <NUM> were simultaneously driven.

Gas detection experiments were performed in the same manner as in Example <NUM> except that gas detection was performed at positions p1, p2, p3, p4, p5, p6, and p7 of the cell module assembly <NUM> shown in <FIG>.

It can be seen from the gas detection experiment result for each crack position according to Example <NUM> that the position of the crack formed in the upper surface of the uppermost cell of the cell module assembly was detected. For this reason, the surfaces of the stacked cells that face each other, i.e. the upper surface and the lower surface of each unit cell, form stacked surfaces, whereby an effect similar to a taping effect is achieved, and therefore gas detection due to gas leakage within a short time may be difficult. Consequently, it can be seen that it may be difficult to rapidly detect the positions of cracks formed in the stacked surfaces using the gas detection apparatus for cell module assemblies according to the present invention.

The results of CO<NUM> gas detection according to Example <NUM> are shown in <FIG>.

In Example <NUM>, gas detection experiments were performed on a normal cell module assembly having no crack formed therein and a defective cell module assembly having a crack formed therein using the gas detection method according to the present invention. In this example, a defective cell module assembly having a crack formed at position P2 shown in <FIG> was used. Gas sensors were disposed at the front wall surface and the rear wall surface of the gas detection chamber unit <NUM> so as to be spaced apart from each other by a predetermined distance in a 3x3 matrix, and gas sensors were disposed at the side wall surface of the gas detection chamber unit so as to be spaced apart from each other by a predetermined distance in a 2x3 matrix. In addition, two gas sensors were also disposed at positions adjacent to the front of the upper wall surface of the gas detection chamber unit <NUM> so as to be spaced apart from each other by a predetermined distance. Experiments were performed through a step of transferring the cell module assembly using the sliding die unit <NUM>; a step of moving the gas detection chamber unit <NUM> downwards through downward operation of the stripper <NUM> to receive the cell module assembly in the gas detection chamber unit <NUM>; a step of driving the gas circulation unit <NUM> to circulate gas in the gas detection chamber unit <NUM>; a step of detecting the gas in the gas detection chamber unit <NUM> using the gas sensor unit <NUM>; a step of moving the gas detection chamber unit <NUM> upwards through upward operation of the stripper <NUM> to separate the gas detection chamber unit <NUM> and the sliding die unit <NUM> from each other; and a step of purifying the interior of the gas detection chamber unit <NUM> using the gas circulation unit <NUM>.

The results of gas detection experiments according to Example <NUM> are shown in <FIG>. In the result graph, the period from the start to <NUM> seconds of an x-axis, which indicates time, is a gas detection period, and the period from the <NUM> seconds to <NUM> seconds is a period during which the gas detection chamber unit <NUM> is purified after gas detection is completed. It can be seen from the result graph that gas was not detected as the result of gas detection experiments using the normal cell module assembly and that five gas sensors disposed at the crack position and the upper side, the lower side, the left side, and the right side of the crack position, among <NUM> gas sensors, detected CO<NUM> gas as the result of gas detection experiments using the cell module assembly having the cracks formed therein. The detected CO<NUM> concentration value was greater when the gas sensor was disposed closer to the crack position, and the average CO<NUM> concentration value of the gas sensor disposed closest to the crack position was the greatest. Consequently, it can be seen that it is possible to determine whether the battery cell is damaged based on whether CO<NUM> is detected by the gas sensor and that it is possible to determine a damaged cell and the damaged position of the cell based on comparison in CO<NUM> concentration values detected by the gas sensors.

Claim 1:
A gas detection apparatus (<NUM>) for cell module assemblies (<NUM>) constituted by stacked battery cells (<NUM>), the gas detection apparatus comprising:
a gas detection chamber unit (<NUM>) configured to receive a cell module assembly (<NUM>); and
a sliding die unit (<NUM>) configured to be movable to a lower part of the gas detection chamber unit (<NUM>) when the cell module assembly (<NUM>) is disposed at an upper end of the sliding die unit (<NUM>),
wherein the gas detection apparatus (<NUM>) further comprises a gas sensor unit (<NUM>) provided in the gas detection chamber unit (<NUM>), the gas sensor unit (<NUM>) comprising a plurality of gas sensors (<NUM>, 131a, 131b) disposed at positions corresponding to positions of cells (<NUM>) of the cell module assembly (<NUM>),
characterised in that
the plurality of gas sensors (<NUM>, 131a, 131b) of the gas sensor unit (<NUM>) are provided at an outer wall of the gas detection chamber unit (<NUM>) so as to be disposed at the battery cells (<NUM>) constituting the cell module assembly (<NUM>) and at predetermined positions (P, P1-P7) of the stack of battery cells (<NUM>) in a state where the cells (<NUM>) are spaced apart from each other by a predetermined distance,
the gas detection apparatus (<NUM>) further comprising a pressing unit (<NUM>) provided in the gas detection chamber unit (<NUM>), the pressing unit (<NUM>) being configured to press an upper part of the cell module assembly (<NUM>).