Abstract:
A laser cleaning device, and a laser cleaning method using the same, for removing an electrolyte solution stuck to an electrolyte tab during a process of injecting the electrolyte solution are disclosed. The laser cleaning device for an electrode tab of a battery includes: a cleaning housing, in which a battery case for receiving an electrode group, an electrolyte solution and an electrode tab exposed to the outside are embedded; a laser generator which includes a laser source for generating a laser beam and an output controller for controlling output of the laser beam; a laser transmitter which transmits the laser beam generated by the laser generator; and a laser emitting unit which is installed inside the cleaning housing, and which irradiates the laser beam transmitted by the laser transmitter onto the electrode tab so as to remove liquid pollutants stuck to the electrode tab. The laser cleaning method comprises steps generally corresponding to the latter functions of the laser cleaning device.

Description:
CLAIM OF PRIORITY 
       [0001]    This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application filed in the Korean Intellectual Property Office on May 28, 2010 and there duly assigned Serial No. 10-2010-0050491. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to a laser cleaning device for an electrode tab of a battery and, more particularly, to a laser cleaning device for removing an electrolyte solute stuck to an electrode tab during a process of injecting electrolyte, and a laser cleaning method using the same. 
         [0004]    2. Description of the Related Art 
         [0005]    A battery can be classified into a primary battery which cannot be charged and a rechargeable battery which can be charged. Among those, a low-capacity primary battery or rechargeable battery has been used as a power supply for portable small electronic devices, such as a mobile phone, a notebook computer and a camcorder, and a large-capacity rechargeable battery has bee used as a power supply for driving a motor, such as a hybrid car, an electric car, etc. 
         [0006]    The battery basically includes: an electrode group including a positive electrode, a negative electrode, and a separator; a case for receiving the electrode group together with an electrolyte solution; and a cap assembly for sealing the case. In the case of a cylindrical battery, the positive electrode may be electrically connected to a cap assembly and a negative electrode may be electrically connected to the case. To this end, a positive tab attached to the positive electrode may be fixed to an inner side of the cap assembly, and a negative tab attached to the negative electrode may be fixed to an inner side of the case. 
         [0007]    Since a general cylindrical battery does not have an electrolyte solution injection hole, it is subjected to a process of inserting the electrode group into the case, injecting the electrolyte into the case, mounting the cap assembly on the case, and then sealing the case. The negative tab is fixed to the case before the electrolyte solution injection, the positive tab is fixed to the cap assembly after the electrolyte solution injection, and the cap assembly to which the positive tab is fixed is mounted on the case together with a gasket. 
         [0008]    As described above, in the structure where the electrolyte solution is injected into the case and then the cap assembly is mounted, the electrolyte solution is stuck to the electrode tab, for example, the positive tab. In this case, since the conductive characteristics and assembling performance of the electrode tab are degraded, the electrolyte solution stuck to the electrode tab should be removed. However, since the electrode tab has a very small thickness of approximately 0.1 mm, it is required to pay careful attention to the handling of the electrode tab, and secondary foreign materials should not occur in the cleaning process. 
         [0009]    The above information disclosed in this Background section is only for enhancement of an understanding of the background of the described technology, and therefore it may contain information that does not form the prior art which is already known in this country to a person of ordinary skill in the art. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention has been developed in an effort to provide a laser cleaning device for an electrode tab of a battery having the advantages of effectively removing an electrolyte solution stuck to an electrode tab after injecting an electrolyte solution, simplifying system configuration, and improving productivity, and a laser cleaning method using the same. 
         [0011]    An exemplary embodiment provides a laser cleaning device for an electrode tab of a battery, the device comprising: a cleaning housing in which a battery case for receiving an electrode group, an electrolyte solution and an electrode tab exposed to the outside are embedded; a laser generator which includes a laser source for generating a laser beam and an output controller for controlling output of the laser beam; a laser transmitter which transmits the laser beam generated by the laser generator; and a laser emitting unit which is installed inside the cleaning housing, and which irradiates the laser beam transmitted by the laser transmitter to the electrode tab so as to remove liquid pollutants stuck to the electrode tab. 
         [0012]    The laser source may generate Nd:YAG pulse laser, and energy per pulse of the Nd:YAG pulse laser may be 14 J to 34 J. The laser transmitter may be configured as an optical fiber cable. 
         [0013]    The laser emitting unit may include at least a magnifying optical unit, a modifying optical unit, or a focusing optical unit. The modifying optical unit may include a laser absorption mask in which an opening for determining a shape of the laser beam is formed. The focusing optical unit may include a convex lens and a lens moving unit which changes the position of the convex lens. The laser emitting unit may emit a laser beam having a diameter two to three times larger than the width of the electrode tab. 
         [0014]    The laser cleaning device for the electrode tab of the battery may further include a positional controller which is coupled to the laser emitting unit so as to change the position of the laser emitting unit. 
         [0015]    The laser cleaning device for the electrode tab of the battery may further include an erect device which is installed inside the cleaning housing, and which is connected to the electrode tab so as to erect and spread the electrode tab. The erect device may include a holder unit which pressurizes the electrode tab so as to fix the electrode tab, and a vertical moving unit which moves the holder unit in a vertical direction. 
         [0016]    A plurality of battery cases may be provided at a distance from each other. The laser cleaning device for the electrode tab of the battery may further include a support which supports the plurality of battery cases, and a first transferring unit which is installed on the support and which moves the plurality of battery cases along a defined orbit. 
         [0017]    The erect device may be provided in plural in correspondence to the number of battery cases. The laser cleaning device for the electrode tab of the battery may further include a second transferring unit which is connected to the plurality of erect devices so as to move the plurality of erect devices along the same orbit as the first transferring unit. 
         [0018]    The laser cleaning device for the electrode tab of the battery may further include a laser absorber which is disposed at the rear of the electrode tab in the cleaning housing, and which absorbs the remaining energy of laser beam. 
         [0019]    The laser cleaning device for the electrode tab of the battery may further include an exhaust unit which is installed in the cleaning housing. The exhaust unit may include a dust collecting device which collects and removes pollutants, and an exhaust duct which discharges air from which pollutants are removed to the outside of the cleaning device. 
         [0020]    The laser cleaning device for the electrode tab of the battery may further include a monitoring system which monitors and records the cleaning process of the battery tab. The monitoring system may include a photographing unit which photographs the cleaning process of the battery tab and a display unit which displays image information obtained from the photographing unit. 
         [0021]    Another exemplary embodiment provides a laser cleaning method for an electrode tab of a battery, the method comprising the steps of: mounting a battery case, which receives an electrolyte solution and exposes an electrode tab, in a cleaning housing; generating a laser beam having an output which is controlled by a laser generator; transmitting the laser beam to a laser emitting unit by using a laser transmitter; and setting the shape and size of the laser beam by controlling optical magnification of the laser emitting unit, and then irradiating the laser beam onto the electrode tab. 
         [0022]    In the mounting of the battery case, the electrode tab may be erected and spread by using the erect device. The electrode tab may be erected so as to be maintained at an angle of 80° to 100° with respect to the irradiation direction of the laser beam. 
         [0023]    In the irradiating of the laser beam, the diameter of the laser beam may be two to three times the width of the electrode tab. In the irradiating of the laser beam, a laser absorber may be disposed in the rear of the electrode tab so as to absorb the remaining energy of the laser beam. In the irradiating of the laser beam, pollutants may be collected and removed during the laser cleaning process by using the dust collecting device. 
         [0024]    According to the exemplary embodiments, the electrolyte solution stuck to the electrode tab is vaporized and removed using the thermal energy of the laser beam. The laser cleaning technology can effectively clean an electrode tab having a small thickness without applying friction to the electrode tab, it does not damage the electrode tab or cause secondary pollution, it simplifies the system configuration, and it improves productivity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components, wherein: 
           [0026]      FIG. 1  is a configuration diagram showing a laser cleaning device for an electrode tab of a battery according to an exemplary embodiment; 
           [0027]      FIG. 2  is a configuration diagram showing a laser emitting unit in the laser cleaning device shown in  FIG. 1 ; 
           [0028]      FIG. 3  is a schematic diagram showing an erect device in the laser cleaning device shown in  FIG. 1 ; 
           [0029]      FIG. 4  is a schematic diagram showing a battery case and a support in the laser cleaning device shown in  FIG. 1 ; 
           [0030]      FIG. 5  is a schematic diagram showing an electrode tab and a laser absorber in the laser cleaning device shown in  FIG. 1 , wherein an erect device is omitted for convenience; 
           [0031]      FIG. 6  is a flowchart showing a laser cleaning method for an electrode tab of a battery according to an exemplary embodiment; and 
           [0032]      FIG. 7  is a schematic diagram showing an electrode tab at a first step shown in  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    Hereinafter, the present invention will be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art will realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
         [0034]      FIG. 1  is a configuration diagram showing a laser cleaning device for an electrode tab of a battery according to an exemplary embodiment. 
         [0035]    Referring to  FIG. 1 , a laser cleaning device  100  according to an exemplary embodiment includes a cleaning housing  10 , a laser generator  20 , a laser transmitter  30 , and a laser emitting unit  40 . The operations of each member included in the laser cleaning device  100  are controlled by an integrated controller  11 . 
         [0036]    The laser generator  20  generates laser beam (LB) for removing an electrolyte solution which is a liquid pollutant stuck to the electrode tab  12 . The laser generator  20  includes a laser source  21  which generates the laser beam LB and an output controller  22  which controls the output of the laser beam (LB). The output controller  22  is connected to the integrated controller  11  so as to output the laser beam (LB) according to a control signal of the integrated controller  11 . 
         [0037]    As the laser beam (LB), a Nd:YAG pulse laser having a pulse width of 1,064 nm may be used. The laser beam (LB) vaporizes the electrolyte solution stuck to the electrode tab  12  using thermal energy so as to clean the electrode tab  12 . The laser cleaning does not apply friction to the electrode tab  12 , thereby making it possible to effectively clean the electrode tab  12  having a small thickness. 
         [0038]    The energy per the pulse of the laser beam (LB) may be 14 J to 34 J. If energy per pulse of the laser beam (LB) is smaller than 14 J, it is impossible to perform the cleaning using the laser beam (LB), and if energy per pulse of the laser beam (LB) is larger than 34 J, the electrode tab  12  may be damaged during the cleaning process. 
         [0039]    The laser generator  20  is positioned outside the cleaning housing  10 , and the laser emitting unit  40  is positioned inside the cleaning housing  10 . The laser transmitter  30  is installed between the laser generator  20  and the laser emitting unit  40  so as to transmit the laser beam (LB) generated by the laser generator  20  to the laser emitting unit  40 . The laser transmitter  30  may be formed as an optical fiber cable. The optical fiber cable is configured as an optical fiber transmitting a laser beam and a coating material surrounding the optical fiber. 
         [0040]    The laser emitting unit  40  emits the laser beam (LB) received from the laser transmitter  30  to the electrode tab  12 . The laser emitting unit  40  includes an optical device therein, thereby making it possible to control the size of the laser beam (LB), energy density (J/cm 2 ) per unit area, and the shape of the laser beam (LB), etc. 
         [0041]      FIG. 2  is a configuration diagram showing a laser emitting unit in the laser cleaning device shown in  FIG. 1 . 
         [0042]    Referring to  FIG. 2 , a magnifying optical unit  42 , a modifying optical unit  43 , and a focusing optical unit  44  are included in the case  41  of the laser emitting unit  40 . The laser emitting unit  40  may use all three optical units or some of three optical units according to the purpose. 
         [0043]    The magnifying optical unit  42  includes a concave lens  421  and a convex lens  422 , and magnifies the laser beam (LB) to a desired magnification by the optical action of the concave lens  421  and the convex lens  422 . The magnifying optical unit  43  includes a laser absorption mask  432  having a center which is formed with an opening  431 . The laser beam (LB) provided at the laser absorption mask  432  is outputted in the same shape as the opening  431  while the edge is absorbed in the laser absorption mask  432 . The laser beam (LB) may be modified in an advantageous shape for cleaning, such as the shape of a circle, an oval, etc. 
         [0044]    The focusing optical unit  44  includes a convex lens  441  and focuses the laser beam (LB) passing through the modifying optical unit  43  so as to implement an energy density having sufficient intensity to perform the cleaning. The focusing optical unit  44  may include a lens moving unit  442  which changes the position of the convex lens  441 . The size of the laser beam (LB) and the energy density of the laser beam (LB) reaching the electrode tab  12  can be easily controlled by changing the position of the convex lens  441  using the lens moving unit  442 . 
         [0045]    Referring back to  FIG. 1 , the laser cleaning device  100  may include a positional controller  46  which moves the laser emitting unit  40  in a horizontal direction and a vertical direction so as to control the light emitting position of the laser beam (LB). The positional controller  46  is installed in an inner wall of the cleaning housing  10 , and moves the laser emitting unit  40  in a direction parallel to the inner wall of the cleaning housing  10 , thereby making it possible to freely control the position of the laser beam (LB). 
         [0046]    The support  14  which supports the battery case  13  is positioned inside the cleaning housing  10 . The battery case  13  includes the electrode group and the electrolyte solution therein. The electrode group includes a positive electrode, a negative electrode, and a separator, wherein a portion of the electrode tab  12  is exposed to the outside of the battery case  13 . 
         [0047]    The electrode tab  12  may be a positive tab connected to a positive electrode and a negative tab connected to a negative electrode. On the other hand, two electrode tabs (positive tab and negative tab) may be exposed to the outside of the battery case  13 .  FIG. 1  shows, by way of example, the case where one electrode tab  12  is exposed to the outside of the battery case  13 . 
         [0048]    After the injection of the electrolyte solution is completed, the electrode tab  12  is in a state wherein it has fallen or is inclined in any one direction. In this state, since the laser beam (LB) cannot be irradiated onto the electrode tab  12 , the electrolyte solution stuck to the electrode tab  12  cannot be removed. Therefore, the laser cleaning device  100  includes an erect device  50  which erects and spreads the electrode tab  12  and facilitates the laser cleaning device. 
         [0049]      FIG. 3  is a schematic diagram showing an erect device in the laser cleaning device shown in  FIG. 1 . 
         [0050]    Referring to  FIG. 3 , the erect device  50  includes a holder unit  51  which fixes the electrode tab  12  by pressing the electrode tab  12  and a holder unit  51 , and a vertical moving unit  52  which moves the holder unit  51  in a vertical direction. The holder unit  51  may be configured of tongs. The vertical moving unit  52  may include a linear motion device connected to the holder unit  51 , and a cam  54  which drives the linear motion device  53 . The vertical moving unit  52  may be formed of a combination of other mechanical devices other than the exemplary embodiment shown in  FIG. 3 . 
         [0051]    When the holder unit  51  fits in the electrode tab  12  and the cam  54  is then driven, the electrode tab  12  fixed to the holder unit  51  is flatly spread while being erected by a backward action. Therefore, the surface area of the electrode tab  12  onto which the laser beam (LB) is irradiated is expanded, thereby making it possible to improve the cleaning efficiency by the laser beam (LB). The electrode tab  12  may maintain an angle of 80° to 100° with respect to the irradiation direction of the laser beam (LB). 
         [0052]    Referring back to  FIG. 1 , a plurality of battery cases  13  are included in the cleaning housing  10 , and the plurality of battery cases  13  may move along the defined orbit and reach the cleaning position one by one. The cleaning position is defined as a position which receives the laser beam (LB), facing the laser emitting unit  40 . 
         [0053]      FIG. 4  is a schematic diagram showing a battery case and a support in the laser cleaning device shown in  FIG. 1 . 
         [0054]    Referring to  FIG. 4 , the support  14  includes a plurality of supporting holders  141  to support the plurality of battery cases  13  at a predetermined distance. The lower portion of the support  14  is provided with the first transferring unit  15  to move the support  14  and the battery case  13  along the defined orbit. The first transferring unit  15  may move the support  14  in a straight direction or it may move the support  14  along an orbit in the shape of a closed curved line, such as a circle, an oval, etc. 
         [0055]    In this case, the plurality of erect devices  50  are provided in correspondence to the number of battery cases  13 , and the second transferring unit  16  is provided on the upper portions of the erect devices  50  so as to move the plurality of erect devices  50  along the same orbit as the first transferring unit  15 . The first transferring unit  15  and the second transferring unit  16  are configured as a combination of a rack gear, a pinion gear and a motor, or may be configured as a combination of other mechanical devices. 
         [0056]    The electrode tab  12  of the battery case  13  which is disposed at the cleaning position receives the laser beam (LB) so as to perform the cleaning operation. Then, the first transferring unit  15  and the second transferring unit  16  are operated, and they dispose and stop the electrode tab  12  of the battery case  13 . Then, the electrode tab  12  of the battery case  13  disposed at the cleaning position receives the laser beam (LB), thereby performing the cleaning operation. In this case, while the first transferring unit  15  and the second transferring unit  16  are operated, the laser source  21  is turned off so that the laser beam (LB) is not emitted. By a repeated process, the plurality of electrode tabs  12  can be continuously cleaned. 
         [0057]    Referring back to  FIG. 1 , the laser cleaning device  100  includes a laser absorber  17  which is disposed at the rear of the electrode tab  12  in the cleaning housing  10 . The laser absorber  17  is disposed so as to face the laser emitting unit  40 , putting the electrode tab  12  therebetween, and is formed so as to have a larger area than the electrode tab  12 . 
         [0058]    A diameter of the laser beam (LB) reaching the electrode tab  12  is set to be larger than a width of the electrode tab  12  in order to smoothly clean the electrode tab  12 . Thereby, a portion of the laser beam (LB) reaches the electrode tab  12  so as to vaporize the electrode solution stuck to the electrode tab  12 , but the remaining portion is diffused to the inside of the cleaning housing  10 . In this case, the laser absorber  17  receives the laser beam (LB) which does not reach the electrode tab  12 , thereby absorbing the remaining energy of the laser beam (LB). 
         [0059]    If it is assumed that there is no laser absorber  17 , the laser beam which does not reach the electrode tab  12 , among the laser beam (LB) emitted from the laser emitting unit  40 , reaches other members in the cleaning housing  10 , and damages them or diffuses in several directions in the cleaning housing  10  so as to cause the fault of other members. However, the laser cleaning device  100  according to the present exemplary embodiment includes the laser absorber  17  so as to solve the above-mentioned problem. 
         [0060]    The laser cleaning device  100  include an exhaust unit  60  that safely removes the pollutants generated during the cleaning process. The exhaust unit  60  includes a blower  61  which sucks air including pollutants, a dust collecting device  62  which collects and removes the pollutants, and an exhaust duct  63  which discharges air from which pollutants are removed to the outside of the cleaning housing  10 . The exhaust unit  60  may be disposed just on the battery case  13  and the erect device  50  in order to rapidly remove the pollutants. The pollutants can be safely removed by using the above-mentioned exhaust unit  60 . 
         [0061]    Furthermore, the laser cleaning device  100  includes a monitoring system which monitors and records the cleaning process of the electrode tab  12 . The monitoring system includes a photographing unit  71  which photographs the cleaning process of the electrode tab  12  and a display unit  72  which displays the image information obtained by the photographing unit  71 . The photographing unit  71  may be fixed to the inside of the cleaning housing  10  (for example, the casing  41  of the laser emitting unit  40 ), and the display unit  72  is disposed outside the cleaning housing  10 . 
         [0062]      FIG. 5  is a schematic diagram showing an electrode tab and a laser absorber in the laser cleaning device shown in  FIG. 1 . An erecting device is omitted for convenience in  FIG. 5 . 
         [0063]    Referring to  FIG. 5 , the electrode tab  12  has predetermined width W and length L, and is formed so as to have a thickness of approximately 1 mm. For example, the width W of the electrode tab  12  may be approximately 3 mm and the length L of the electrode tab  12  exposed to the outside of the battery case  13  may be approximately 6 mm. 
         [0064]    The laser beam (LB) may be a circle, and the diameter D of the laser beam (LB) reaching the electrode tab  12  may be two to three times as large as the width W of the electrode tab  12 . The laser beam (LB) is irradiated onto one surface of the electrode tab  12  facing the laser emitting unit  40 , but the electrolyte solution stuck to an opposite surface of the electrode tab  12  is vaporized and removed together by the thermal transfer of the electrode tab  12 . 
         [0065]    If it is determined that the diameter of the laser beam (LB) is two times smaller than the width W of the electrode tab  12 , at least one of the position of the laser beam (LB) and the position of the electrode tab  12  should be very precisely controlled, such that additional processes are required. Meanwhile, if it is determined that the diameter of the laser beam (LB) exceeds three times the width W of the electrode tab  12 , the energy density per unit area of the laser beam (LB) is low, such that the cleaning effect is deteriorated. 
         [0066]      FIG. 6  is a flowchart showing a laser cleaning method for an electrode tab of a battery according to an exemplary embodiment. 
         [0067]    Referring to  FIG. 6 , a laser cleaning method for an electrode tab of a battery according to the exemplary embodiment includes: a first step (S 10 ) of mounting the battery case, from which the electrode tab is exposed, in the cleaning housing; a second step (S 20 ) of generating the laser beam for controlling the output by using the generator; a third step (S 30 ) of transmitting the laser beam to the laser emitting unit in the cleaning housing by the laser transmitter; and a fourth step (S 40 ) of controlling the optical magnification of the laser emitting unit so as to emit the optimized laser beam to the electrode tab. 
         [0068]    In the first step S 10 , the electrode tab  12  may be straightly erected and spread by using the erect device  50  installed in the cleaning housing  10 .  FIG. 7  is a diagram schematically showing the electrode tab at the first step shown in  FIG. 6 , wherein the electrode tab  12  may be maintained at an angle θ of 80° to 100° with respect to the irradiation direction of the laser beam (LB). If it is determined that the angle θ of the electrode tab  12  is smaller than 80° or exceeds 100°, the energy density per the unit area of the laser beam (LB) is low, such that the cleaning efficiency is deteriorated. 
         [0069]    In addition, the plurality of battery cases  13  are installed in the cleaning housing  10  and the plurality of battery cases may be sequentially positioned one by one by using the first transferring unit  15  and the second transferring unit  16 . 
         [0070]    In the second step S 20 , the laser beam may be the Nd:YAG pulse laser and the energy per pulse of the laser beam (LB) may be 14 J to 34 J. 
         [0071]    In the fourth step, the laser emitting unit  40  uses at least one of the above-mentioned magnifying optical unit  42 , the modifying optical unit  43 , and the focusing optical unit  44  to control the shape and size of the laser beam (LB) and the energy density per unit area, and emit the controlled laser beam (LB) to the electrode tab  12 . 
         [0072]    In this case, the size of the laser beam (LB) is larger than the area of the electrode tab  12  exposed to the outside of the battery case  13 , and the diameter of the laser beam (LB) is set so as to be two to three times larger than the width of the electrode tab  12 . The electrode tab  12  receiving the laser beam (LB) is cleaned, while the electrolyte solution stuck to the surface is vaporized by the thermal energy of the laser beam (LB). In addition, the laser absorber  17  is positioned at the rear of the electrode tab  12 , thereby absorbing the remaining energy of the laser beam (LB). 
         [0073]    The pollutants, such as fume, generated during the laser cleaning process are collected in the dust collecting device  62  installed in the cleaning housing  10 , and are safely removed. The above-mentioned laser cleaning technology does not apply the friction to the electrode tab  12 , such that it is efficient in cleaning the electrode tab  12  having a small thickness, and the damage or secondary pollution of the electrode tab  12  does not occur. 
         [0074]    While this disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.