Abstract:
Embodiments of the present invention facilitate a winding process and enable auxiliary current collectors to be securely fixed to a main current collector, thereby minimizing deformation during battery charging and discharging and maintaining sufficient strength. The jelly roll includes a first auxiliary current collector, a second auxiliary current collector, a mandrel insulating layer, and an electrode plate. The first auxiliary current collector and the second auxiliary current collector are spaced apart from each other and each has a mandrel protrusion on an opposite end portion. The mandrel insulating layer insulates the auxiliary current collectors from each other and insulates the auxiliary current collectors from an exterior. The electrode plate is formed by layering a separator, a first electrode plate, a separator and a second electrode plate and is wound on an external surface of the mandrel insulating layer.

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on 19 Aug. 2010 and there duly assigned Serial No. 10-2010-0080290. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     One embodiment of the present invention relates to a jelly roll and an electrode assembly having the same, and more particularly, to a jelly roll which facilitates a process and has structural stability and an electrode assembly having the jelly roll. 
     2. Discussion of Related Art 
     A secondary battery is a chemical cell which may be repeatedly charged and discharged via reversible conversion between chemical energy and electrical energy. Recently, since telecommunication equipment is widely used and automotive batteries require a higher capacity and a higher output emerge, lithium secondary batteries having a higher voltage and a higher capacity density are required. 
     Although various materials may be used to form a battery, materials having a high charging and discharging capacity in a potential range for practical use is generally used in order to obtain a battery having a high capacity. Capacity may be classified into specific capacity that is a weight characteristic and capacity density that is a volume characteristic. A high quality battery generally has both a high specific capacity and a high capacity density and contains high-density materials. 
     Meanwhile, a lithium-ion secondary battery mainly includes a positive active material, a negative active material, an electrolyte, and a separator. The positive active material generally includes LiCO 2 , and the negative active material generally includes carbon materials, such as graphite, occluding and emitting lithium as ions. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a jelly roll which is easy to be made by a winding process. 
     Another aspect of the present invention provides an electrode assembly including a terminal and a current collector and eliminating unnecessary space within the electrode assembly. The size of such electrode assembly may be advantageously minimized. 
     Still another aspect of the present invention provides an electrode assembly in which a jelly roll is securely settled during fabrication, and is thus physically stable after the completion of manufacture in order to minimize deformation occurring during charging and discharging and to have a strong structure against external impact. 
     In accordance with an embodiment of the present invention, a jelly roll may include a first auxiliary current collector, a second auxiliary current collector, a mandrel insulating layer, and an electrode plate. The first auxiliary current collector and the second auxiliary current collector are spaced apart from each other and each have a mandrel protrusion on a respective opposite end portion. The mandrel insulating layer insulates the auxiliary current collectors from each other and insulates the auxiliary current collectors from an exterior. The electrode plate is formed by layering a separator, a first electrode plate, a separator and a second electrode plate in sequence and the electrode plate may be wound on an outer surface of the mandrel insulating layer. 
     The first electrode plate includes a positive active material layer to which a positive active material is applied and a positive non-applied part to which the positive active material is not applied, and the second electrode plate includes a negative active material layer to which a negative active material is applied and a negative non-applied part to which the negative active material is not applied. Here, the electrode plates may be deposited with the positive non-applied part being exposed to one edge of the separator and the negative non-applied part being exposed to another opposite edge of the separator. 
     The first auxiliary current collector may include an alloy of at least one of aluminum, nickel, titanium and plastic carbon. 
     The second auxiliary current collector may include an alloy of at least one of copper, stainless steel, aluminum and nickel. 
     Two or more mandrel protrusions may be formed on each auxiliary current collector. 
     In accordance with another embodiment of the present invention, an electrode assembly may include a first auxiliary current collector, a second auxiliary current collector, a mandrel insulating layer, an electrode plate, a first main current collector, and a second main current collector. 
     The first auxiliary current collector and the second auxiliary current collector are spaced apart from each other and each have a mandrel protrusion on a respective opposite end portion. The mandrel insulating layer insulates the auxiliary current collectors from each other and insulates the auxiliary current collectors from an outside. The electrode plate is formed by layering a separator, a first electrode plate, a separator and a second electrode plate in sequence and the electrode plate is wound on an outer surface of the mandrel insulating layer. Each of the first and second main current collectors includes a side plate in which a mandrel protrusion accommodating hole to accommodate the mandrel protrusion is formed and a cap plate extending from an edge of the side plate in a perpendicular direction. An electrode terminal is formed on the cap plate. A current collector insulating part connects the cap plate of the first main current collector with the cap plate of the second main current collector. 
     Further, the first main current collector, the second main current collector, and the current collector insulating part may be simultaneously and integrally formed as a single body. 
     Further, the first electrode plate may include a positive active material layer to which a positive active material is applied and a positive non-applied part to which the positive active material is not applied, and the second electrode plate comprises a negative active material layer to which a negative active material is applied and a negative non-applied part to which the negative active material is not applied. Here, the electrode plates are deposited with the positive non-applied part being exposed to one edge of the separator and the negative non-applied part being exposed to another opposite edge of the separator. 
     In addition, an adhesive inlet injecting an adhesive may be formed in the side plate of the first main current collector and in the side plate of the second main current collector. 
     Further, an adhesive injected into the adhesive inlet may be electrically conductive. Also, the adhesive may adhere the first main current collector to the positive non-applied part and may adhere the second main current collector to the negative non-applied part. 
     The adhesive may adhere the first auxiliary current collector to the positive non-applied part and may adhere the second auxiliary current collector to the negative non-applied part. 
     Further, two or more mandrel protrusions may be formed on each auxiliary current collector. 
     In addition, at least one adhesive inlet may be provided between the mandrel protrusions. 
     A conductive adhesive may be injected into the adhesive inlet. 
     The mandrel protrusion accommodating hole and the mandrel protrusions inserted into the mandrel protrusion accommodating hole may be welded together. 
     As described above, according to embodiments of the present invention, an auxiliary current collector functioning as a mandrel in a winding process is provided to facilitate the winding process. 
     Moreover, unnecessary space may be eliminated in order to increase a total density of a secondary battery maximally, thereby manufacturing the batter with a high output. 
     In addition, an auxiliary current collector is securely fixed to a main current collector, so that deformation of a secondary battery is minimized in charging and discharging and sufficient strength is maintained when dropped. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is an oblique view illustrating an auxiliary current collector constructed as an embodiment; 
         FIG. 2  is an oblique view illustrating an auxiliary current collector and a mandrel insulating layer constructed as the embodiment; 
         FIG. 3A  is an exploded partial plan view illustrating an electrode plate; 
         FIG. 3B  is a partial cross-sectional view illustrating the electrode plate deposited; 
         FIG. 4A  is an oblique view illustrating winding a jelly roll according to an embodiment. 
         FIG. 4B  is an oblique view illustrating a wound jelly roll constructed as an embodiment; 
         FIG. 4C  is an oblique view illustrating a stack constructed as an embodiment; 
         FIG. 5  is an oblique view illustrating a current collector constructed as an embodiment; 
         FIG. 6  is an oblique view illustrating a current collector and a jelly roll being connected; and 
         FIG. 7  is a schematic view illustrating a process of applying an adhesive. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, only certain embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. In addition, when an element is referred to as being “on” another element, it can be directly on the other element or be indirectly on the other element with one or more intervening elements interposed therebetween. Also, when an element is referred to as being “connected to” another element, it can be directly connected to the other element or be indirectly connected to the other element with one or more intervening elements interposed therebetween. Hereinafter, like reference numerals refer to like elements. 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the specification, terms to indicate directions “up,” “down,” “right,” and “left” are based on directions in the drawings unless the context clearly indicates otherwise. 
     An electrode assembly may include a jelly roll  100  and a current collector  200  as shown in  FIGS. 4B ,  5  and  6 . In another embodiment, an electrode assembly may include a stack  100   a  and a current collector  200  as shown in  FIGS. 4C ,  5  and  6 . 
     As shown in  FIG. 4B , the jelly roll  100  may include an auxiliary current collector  110 , a mandrel insulating layer  120 , and an electrode plate  150 . 
     As shown in  FIG. 4C , the stack  100   a  may include an auxiliary current collector  110 , a mandrel insulating layer  120 , and a stacked type electrode plate  150   a.    
       FIG. 1  is an oblique view illustrating an auxiliary current collector constructed as an embodiment. As shown in  FIG. 1 , the auxiliary current collector  110  includes a first auxiliary current collector  110   a  and a second auxiliary current collector  110   b . In one embodiment, the first auxiliary current collector  110   a  may act as a positive auxiliary current collector, and the second auxiliary current collector  110   b  may act as a negative auxiliary current collector. In another embodiment, the first auxiliary current collector  110   a  may act as a negative auxiliary current collector, and the second auxiliary current collector  110   b  may act as a positive auxiliary current collector. For convenience of description, the first auxiliary current collector  110   a  is thereafter referred to as a positive auxiliary current collector, and the second auxiliary current collector  110   b  is thereafter referred to as a negative auxiliary current collector. 
     The positive auxiliary current collector  110   a  and the negative auxiliary current collector  110   b  may be formed in a rectangular plate shape. The positive auxiliary current collector  110   a  and the negative auxiliary current collector  110   b  may be disposed spaced apart from each other. In one embodiment, one side Sa 1  of the positive auxiliary current collector  110   a  may be disposed to face toward one side Sb 1  of the negative auxiliary current collector  110   b , and the positive auxiliary current collector  110   a  may be aligned with the negative auxiliary current collector  110   b  in a same plane. A mandrel protrusion  111  is formed on an end portion Sa 2  of the positive auxiliary current collector  110   a  opposite to the negative auxiliary current collector  110   b , and another mandrel protrusion  111  is formed on an end portion Sb 2  of the negative auxiliary current collector  110   b  disposed opposite to the positive auxiliary current collector  110   a . In one embodiment, the mandrel protrusion  111  formed on the positive auxiliary current collector  110   a  protrudes away from the negative auxiliary current collector  110   b ; another mandrel protrusion  111  formed on the negative auxiliary current collector  110   b  protrudes away from the positive auxiliary current collector  110   a . The mandrel protrusions  111  function as a mandrel when an electrode plate  150  is wound into a jelly roll (see  FIG. 4A ). In one embodiment, a pair of mandrel protrusions  111  may be formed on one side of each of auxiliary current collectors. Here, two or more mandrel protrusions  111  may be formed on a single auxiliary current collector so that the mandrel protrusions  111  may be settled securely in a winder  300  (see  FIG. 4A ). 
     The positive auxiliary current collector  110   a  may include aluminum (Al) or an aluminum alloy, and the negative auxiliary current collector  110   b  may include copper (Cu) or a copper alloy. 
       FIG. 2  is an oblique view illustrating an auxiliary current collector and a mandrel insulating layer constructed as the embodiment. As shown in  FIG. 2 , the mandrel insulating layer  120  includes an insulating material and may be formed via molding in order to encompass an outside of the auxiliary current collectors  110 . The mandrel insulating layer  120  insulates the positive auxiliary current collector  110   a  and the negative auxiliary current collector  110   b  from each other, and insulates the auxiliary current collectors  110  from an electrode plate  150  which is wounded around the auxiliary current collectors  110 . The mandrel insulating layer  120  may be formed by electrical insulating material. 
     Referring to  FIGS. 3A and 3B , the electrode plate  150  is described.  FIG. 3A  is an exploded partial plan view illustrating the electrode plate, and  FIG. 3B  is a partial cross-sectional view illustrating the electrode plate. The electrode plate  150  includes a first electrode plate  160 , a second electrode plate  170 , and a separator  180 . In one embodiment, the first electrode plate  160  may be a positive electrode plate, and the second electrode plate  170  may be a negative electrode plate. In another embodiment, the first electrode plate  160  may be a negative electrode plate, and the second electrode plate  170  may be a positive electrode plate. For convenience of description, the first electrode plate  160  is thereafter denoted as positive, and a second electrode plate  170  is thereafter denoted as negative. 
     The positive plate  160  includes a positive active material layer  161  in which a positive active material is applied to both surfaces or one surface of a positive current collector and a positive non-applied part  162  to which the positive active material is not applied. The positive current collector generally uses material having a high conductivity and a high chemical stability. For example, the positive current collector may include aluminum, nickel, titanium, plastic carbon, and the like. The positive active material layer  161  may be formed by applying slurry to the positive current collector, with the slurry being prepared by mixing a positive active material, a conductive material, and a binder with a solvent. 
     The negative plate  170  includes a negative active material layer  171  in which a negative active material is applied to both surfaces or one surface of a negative current collector and a negative non-applied part  172  to which the negative active material is not applied. The negative plate  170  may include conductive metal, for example, copper, stainless steel, aluminum, nickel, and the like. The negative active material layer  171  may be formed by applying slurry to a negative current collector, with the slurry being prepared by mixing a negative active material and a binder to improve coherence of the negative active material with a solvent. 
     The separator  180  may be interposed between the positive active material layer  161  and the negative active material layer  171 . The separator  180  functions as a passage of ions and prevents a direct contact between the positive plate  160  and the negative plate  170 . Thus, the separator  180  is formed of an insulating thin film having a high ion permeability and a high mechanical strength. In one embodiment, the separator  180  may be formed of an electrical insulating thin film. For example, the separator  180  may use a porous film including polyethylene, polypropylene or polyvinylidene fluoride, or felt. 
     An electrode assembly used for a secondary battery may be classified into a winding-type electrode assembly, a deposition-type electrode assembly, and the like. The winding-type electrode assembly is formed by winding a positive plate and a negative plate being insulated from each other by a separator, and the positive and negative plates are sheets extending longitudinally. In the winding-type electrode assembly, the capacity of a battery may be increased by increasing the number of windings. As the number of windings increases, however, the electrode plates or the separator which constitute the electrode assembly may be detached and be easily deformed. Furthermore, the positive plate may come into a direct contact with the negative plate, so that a short circuit may occur. 
       FIG. 3B  shows a cross-sectional view of a layered structure of the electrode plate  150 . As shown in  FIG. 3B , the electrode plate  150  may be formed by layering the separator  180 , the positive plate  160 , the separator  180 , and the negative plate  170  in order. Here, the positive plate  160 , the separator  180 , the negative plate  170 , and the separator  180  may be layered in order, since the above layered structure is repeated in winding. 
     As described above, the positive plate  160  includes the positive active material layer  161  and the positive non-applied part  162 , and the negative plate  170  includes the negative active material layer  171  and the negative non-applied part  172 . When the positive plate  160  is deposited on the separator  180 , the positive non-applied part  162  is exposed to one side (or edge) S 1  of the separator  180 . Likewise, when the negative plate  170  is deposited on the separator  180 , the negative non-applied part  172  is exposed to another side (or edge) S 2  of the separator  180 . When the electrode plate  150  is wound, as shown in  FIG. 4B , the positive non-applied part  162  is exposed to one side S 1  of the separator  180 , and the negative non-applied part  172  is exposed to the other side S 2  of the separator  180 . When the electrode plate  150  is wound into a jelly roll, in one embodiment, the positive non-applied part  162  is uncovered by the separator  180  and is exposed at one edge S 1  of the separator  180 ; the negative non-applied part  172  is uncovered by the separator  180  and is exposed at an opposite edge S 2  of the separator  180 . 
       FIGS. 4A and 4B  show a winding process.  FIG. 4A  is an oblique view illustrating a process of winding the jelly roll  100 , and  FIG. 4B  is an oblique view the wound jelly roll  100 . 
     The winder  300  is a device for winding the electrode plate  150  on an outside of the mandrel insulating layer  120 . The winder  300  includes a mandrel protrusion fixing unit  310  to accommodate and settle the mandrel protrusions  111  on a rotation shaft of a sub-motor and performs a winding process. Here, the alignment of the positive plate  160 , the separator  180 , and the negative plate  170  is important, and thus winding is uniformly performed. 
     The auxiliary current collectors  110  may be wound in a situation where only the mandrel protrusions are exposed to the exterior of the jelly roll in view of risk of a short circuit. 
       FIG. 4C  is an oblique view illustrating a stack constructed as another embodiment. As shown in  FIG. 4C , a stack  100   a  may include an auxiliary current collector  110 , a mandrel insulating layer  120 , and a stacked type electrode plate  150   a . The difference between  FIG. 4B  and  FIG. 4C  is that  FIG. 4C  shows a stacked type electrode plate  150   a  which is different from the jelly roll type electrode plate  150  of  FIG. 4B . The stacked type electrode plate  150   a  is formed by stacking layers  1000 . In the stacked type electrode plate  150   a , the positive non-applied part  162   a  is uncovered by the separator  180   a  and is exposed at one edge of the separator  180   a ; the negative non-applied part  172   a  is uncovered by the separator  180   a  and is exposed at an opposite edge of the separator  180   a.    
       FIG. 5  shows an oblique view of the current collector  200 . A main current collector  210  collectively refers to a positive side plate  210   a , a positive cap plate  210   c , a negative side plate  210   b , and a negative cap plate  210   d . The main current collector  210  may be formed by bending one plate twice at a right angle. As shown in  FIG. 5 , two plates, i.e., the side plates  210   a  and  210   b , face towards each other and are disposed opposite to each other. Two side plates  210   a  and  210   b  are physically connected by the cap plates  210   c  and  210   d , and the two side plates  210   a  and  210   b  are electrically insulated from each other by a current collector insulating part  230 . The current collector insulating part  230  may be provided between the two cap plates  210   c  and  210   d  in order to electrically insulate the cap plate  210   c  from the cap plate  210   d . Here, the side plates  210   a  and  210   b , the cap plates  210   c  and  210   d , and the current collector insulating part  230  may be simultaneously and integrally formed as a single body via double injection molding, or may be manufactured separately and combined via soldering or welding. 
     A mandrel protrusion accommodating hole  212  is formed in the side plates  210   a  and  210   b . The mandrel protrusion accommodating hole  212  may be a through hole. The mandrel protrusions  111  formed on the auxiliary current collectors  110   a  and  110   b  may be inserted into the mandrel protrusion accommodating hole  212 . Further, an adhesive inlet  211  may be formed in the side plates  210   a  and  210   b . The adhesive inlet  211  may be a through hole. In one embodiment, adhesive inlet  211  may be disposed separately from the mandrel protrusion accommodating hole  212 . When the wound jelly roll  100  is put into the current collector  200 , an adhesive may be injected through the adhesive inlet  211  and the adhesive may be disposed to fill a gap between the wound jelly roll  100  and the current collector  200 . Here, the adhesive inlet  211  may be formed between at least two of the mandrel protrusion accommodating holes  212 . When an electrically conductive adhesive is injected through the adhesive inlet  211  provided between the mandrel protrusion accommodating holes  212 , the conductive adhesive may reach up to the auxiliary current collectors  110 . Here, the side plates  210   a  and  210   b  and the cap plates  210   c  and  210   d  may be formed of the same material as the auxiliary current collectors  110 . 
     Referring to  FIG. 6 , a process of connecting the jelly roll  100  to the current collector  200  is described.  FIG. 6  is a perspective view illustrating an assembly where the jelly roll  100  and the current collector  200  are connected to each other. The two mandrel protrusions  111  of the jelly roll  100  may be inserted into the mandrel protrusion accommodating holes  212  formed in the side plates  210   a  and  210   b  of the current collector  200 , so that the jelly roll  100  and the current collector  200  are connected. Here, a jelly roll guide  215  may be provided to guide the inserted jelly roll  100  and to prevent detachment of the positive and negative non-applied parts  162  and  172  formed on opposite sides of the jelly roll  100  after the jelly roll  100  is connected. The jelly roll guide  215  extends from opposite sides (or edges) S 11  and S 22  of the side plates  210   a  and  210   b  toward a direction along the extending direction of the cap plates  210   c  and  210   d.    
     When the connection between the jelly roll  100  and the current collector  200  is completed, as shown in  FIG. 6 , the inside positive or negative non-applied part  162  and  172  may be seen through the adhesive inlet  211 , and the mandrel protrusions  111  inserted from the inside may be seen through the mandrel protrusion accommodating holes  212 . The electrode terminals  241  and  242  are designed to be electrically connected to external electrical devices. 
     Referring to  FIG. 7 , a process of applying an adhesive is described.  FIG. 7  is a schematic view illustrating the process of applying the adhesive. First, an auxiliary side plate  400  is provided parallel with one of the side plates  210   a  and  210   b  side by side. Then, a predetermined amount of an adhesive  420  is applied onto the auxiliary side plate  400 , and the adhesive  420  is spread on up to the side plates  210   a  and  210   b  using a blade  410 . In this manner, the adhesive  420  is put onto the jelly roll  100  through the mandrel protrusion accommodating holes  212  and the adhesive inlet  211 . 
     Here, the adhesive  420  may be an electrically conductive adhesive. The adhesive  420  may attach or adhere the positive side plate  210   a  to the positive non-applied part  162 , and attach or adhere the negative side plate  210   b  to the negative non-applied part  172 . Separately or simultaneously, the adhesive  420  may attach or adhere the positive auxiliary current collector  110   a  to the positive non-applied part  162  and attach or adhere the negative auxiliary current collector  110   b  to the negative non-applied part  172 . 
     In one embodiment where the adhesive  420  is not electrically conductive, a conductive connection member may be additionally provided to respectively electrically connect the non-applied parts  162  and  172  of the electrode plate  150  with the auxiliary current collectors  110   a  and  110   b  or to respectively electrically connect the non-applied parts  162  and  172  of the electrode plate  150  with the side plates  210   a  and  210   b.    
     After applying the conductive adhesive  420 , the conductive adhesive  420  is heated via ultraviolet irradiation or the like so as not to damage a separator of a secondary battery and then the conductive adhesive  420  is hardened at a low temperature. 
     Here, in order to improve connection of the jelly roll  100  and the current collector  200 , the mandrel protrusion accommodating holes  212  and the mandrel protrusions  111  inserted into the mandrel protrusion accommodating holes  212  are welded before injecting the adhesive  420 . 
     Although the spirit of the present invention was described in detail in accordance with the embodiment, it should be understood that the embodiments are provide to explain the present invention and do not limit the present invention, and various jelly rolls and electrode assemblies having the same may be realized without departing from the scope of the present invention. 
     While the present invention has been described in connection with certain 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, and equivalents thereof.