Abstract:
A multi-cell battery includes a negative current collecting substrate; at least two laminated electric cores arranged in parallel to each other on the negative current collecting substrate; and a positive current collecting substrate, wherein the two laminated electric cores sandwiches about the positive current collecting substrate, thereby forming two cells on opposite sides of the positive current collecting substrate.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 61/837,195, filed Jun. 20, 2013, which is included in its entirety herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to batteries. More particularly, the present invention relates to a thin film lithium-ion battery. 
     2. Description of the Prior Art 
     Lithium-ion secondary batteries or lithium-ion batteries have been used as power supplies for personal computers, portable devices such as cell phones, cameras, electric tools, and the like. In secondary batteries, the electron producing and consuming reactions are for the most part reversible, and therefore such a battery can be cycled between a charged and discharged state electrochemically. 
     When the rechargeable battery is charged, ions formed of the cathode material pass from the cathode through the electrolyte to the anode, and when the battery is discharged these ions travel back from the anode through the electrolyte to the cathode. For example, in batteries having a cathode comprising lithium, such as a LiCoO 2  or LiMnO 2  cathode, lithium species originating from the lithium-containing cathode travel from the cathode to the anode and vice versa during the charging and discharging cycles, respectively. 
       FIG. 1  illustrates a conventional structure of a lithium-ion battery. As shown in  FIG. 1 , the lithium-ion battery  1  includes an electrochemical cell comprising an anode active material layer  11  disposed on one side surface of a separator  10 , a cathode active material layer  21  disposed on the other side surface of the separator  10 , an anode current collector  12 , and a cathode current collector  22 . The separator  10  may be made of polymers such as polyimide (PI), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC) or polycarbonate (PC) having porous structure to only allow the passage of the lithium ions, while preventing internal shorting between the anode active material layer  11  and the cathode active material layer  21 . To electrically connect the anode current collector  12  and the cathode current collector  22  to an external circuit or device, the lithium-ion battery  1  may further include two outwardly extended tabs  12   a  and  22   a.    
     Typically, the separator  10 , the anode active material layer  11  and the cathode active material layer  21  are wetted with a liquid electrolyte solution or gel electrolyte. The electrochemical cell is typically enclosed in a parallelepipedic metal case  20  such as an aluminum case in a gas-tight manner with a sealant layer  24  securely sealing a gap between the tabs  12   a  and  22   a.    
       FIG. 2  illustrates another form of a lithium-ion battery known in the art. As shown in  FIG. 2 , the lithium-ion battery  3  is integrated with a circuit substrate  30  such as a copper clad laminate (CCL) substrate. The base dielectric of the CCL substrate may include polyimide (PI), polyethylene terephthalate (PET) or glass fiber. The circuit substrate  30  includes a separator portion  30   a  having therein a plurality of through holes or porous structures for the passage of lithium ions. The separator portion  30   a  is sandwiched by a pair of electrodes  41  and  51 . A current collector  42  is disposed directly on a top surface of the electrode  41 . The electrode  41  is sealed by a packaging unit  43 . Likewise, a current collector  52  is disposed directly on a top surface of the electrode  51 . The electrode  51  is sealed by a packaging unit  53 . Both of the current collectors  42  and  52  are typically made of expensive CCL substrates. The use of CCL substrates increases manufacturing cost/complexity and battery weight. 
     Portable electronic devices have been progressively reduced in size and weight and improved in performance. It is therefore required to develop a rechargeable lithium-ion battery or lithium-ion secondary cell having a high energy density and a high output, which is also cost-effective. Further, after being stored or circled for certain numbers, gas may be generated in lithium-ion batteries, especially at high temperature, which will reduce life span of the lithium-ion battery. What is needed, therefore, is to provide a lithium-ion battery which has desirable life span. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to provide an improved thin film battery that is cost-effective, and has simple structure, high capacity, desirable life span and cycle performance. 
     Another object of the present invention is to provide a thin film battery with improved ability of gas resistance and moisture resistance. 
     According to one embodiment, a thin film lithium-ion battery unit includes a positive current collecting substrate, a positive electrode active material layer coated on an inner surface of the positive current collecting substrate, a negative current collecting substrate, a negative electrode active material layer coated on an inner surface of the negative current collecting substrate, a separator sandwiched between the positive electrode active material layer and the negative electrode active material layer, and electrolyte retained at least in the separator. The positive electrode active material layer, the separator and the negative electrode active material layer constitute a laminated electric core. 
     An outer conductive frame is provided to encompass the positive electrode active material layer with a gap formed therebetween. The outer conductive frame is substantially flush with the positive current collecting substrate. According to one embodiment of the present disclosure, the outer conductive frame may have an opening for accommodating a positive tab that juts out from an edge of the positive current collecting substrate. According to one embodiment of the present disclosure, the outer conductive frame may have a protruding negative tab. A glue layer may be provided to fill the gap. 
     According to another aspect of the invention, a stack structure of a thin-film lithium-ion battery includes an intermediate current collecting substrate having a first surface and a second surface opposite to the first surface; a first laminated electric core laminated on the first surface; a first current collecting substrate laminated on the first laminated electric core, wherein the intermediate current collecting substrate, the first laminated electric core, and the first current collecting substrate constitute a first battery unit; a second laminated electric core laminated on the second surface; a second current collecting substrate laminated on the second laminated electric core, wherein the intermediate current collecting substrate, the second laminated electric core, and the second current collecting substrate constitute a second battery unit; a first sealant layer sealing the first laminated electric core; and a second sealant layer sealing the second laminated electric core. 
     According to still another aspect of the invention, a multi-cell battery includes a negative current collecting substrate; at least two laminated electric cores arranged in parallel to each other on the negative current collecting substrate; and a positive current collecting substrate, wherein said negative current collecting substrate is a folded substrate such that the two laminated electric cores sandwiches about the positive current collecting substrate, thereby forming two cells on opposite sides of the positive current collecting substrate. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the embodiments, and are incorporated in and constitute a part of this specification. The drawings illustrate some of the embodiments and, together with the description, serve to explain their principles. In the drawings: 
         FIG. 1  illustrates a conventional structure of a lithium-ion battery; 
         FIG. 2  illustrates another form of a lithium-ion battery known in the art; 
         FIG. 3  is a schematic top view of an exemplary thin-film lithium-ion battery according to one embodiment of the invention; 
         FIG. 4  is a cross-sectional diagram taken along line I-I′ in  FIG. 3 ; 
         FIG. 5A  and  FIG. 5B  show another embodiment wherein only the seal layer is used; 
         FIGS. 6A-6D  show some variations of the moisture-proof and air-proof packaging structure according to some embodiments of the invention; 
         FIG. 7  is a schematic, cross-sectional diagram illustrating a stack structure of a thin-film lithium-ion battery according to another embodiment of the invention; 
         FIG. 8A  and  FIG. 8B  show irregular outline of the battery cell; 
         FIG. 9  and  FIG. 10  illustrate another embodiment of the present invention, wherein  FIG. 10  is a cross-sectional view taken along line II-II′ of  FIG. 9 . 
         FIG. 11  shows two battery terminal pairs in one the battery cell; 
         FIGS. 12A-12D  show various approaches to sealing the battery cell; 
         FIG. 13A  and  FIG. 13B  show a non-rectangular, terraced battery structure; 
         FIGS. 14A and 14B  show multi-cell batteries according to other embodiments; and 
         FIG. 15  illustrates the manufacturing steps for a three-cell in series battery pack. 
     
    
    
     It should be noted that all the figures are diagrammatic. Relative dimensions and proportions of parts of the drawings are exaggerated or reduced in size, for the sake of clarity and convenience. The same reference signs are generally used to refer to corresponding or similar features in modified and different embodiments. 
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are given to provide a thorough understanding of the invention. It will, however, be apparent to one skilled in the art that the invention may be practiced without these specific details. Furthermore, some well-known system configurations and process steps are not disclosed in detail, as these should be well-known to those skilled in the art. 
     Likewise, the drawings showing embodiments of the apparatus are semi-diagrammatic and not to scale and some dimensions are exaggerated in the figures for clarity of presentation. Also, where multiple embodiments are disclosed and described as having some features in common, like or similar features will usually be described with like reference numerals for ease of illustration and description thereof. 
     The following sets forth a detailed description of a mode for carrying out the invention. The description is intended to be illustrative of the invention and should not be taken to be limiting. It is understood that present invention may be applicable to both primary batteries and secondary batteries, although some embodiments take the secondary battery as an example. 
     Please refer to  FIG. 3  and  FIG. 4 .  FIG. 3  is a schematic top view of an exemplary thin-film lithium-ion battery according to one embodiment of the invention.  FIG. 4  is a cross-sectional diagram taken along line I-I′ in  FIG. 3 . As shown in  FIG. 3  and  FIG. 4 , the lithium-ion battery unit  100  comprises a positive current collecting substrate  102 , a positive electrode active material layer  111  coated on an inner surface of the positive current collecting substrate  102 , a negative current collecting substrate  104 , a negative electrode active material layer  113  coated on an inner surface of the negative current collecting substrate  104 , a separator  112  sandwiched between the positive electrode active material layer  111  and the negative electrode active material layer  113 , and electrolyte (not explicitly shown) retained at least in the separator  112 . The positive electrode active material layer  111 , the separator  112  and the negative electrode active material layer  113  constitute a laminated electric core  110 . The separator  112  between the positive and negative electrodes prevents physical contact of the electrodes while enabling ionic transport. 
     An outer conductive frame  105 , which is spaced apart from the positive current collecting substrate  102 , may be provided to encompass the positive current collecting substrate  102  with a gap  125  formed therebetween. The outer conductive frame  105  is substantially flush or coplanar with the positive current collecting substrate  102 . The outer conductive frame  105  and the positive current collecting substrate  102  are formed in the same horizontal level. According to one embodiment of the present disclosure, the outer conductive frame  105  is not a closed loop shaped frame and may have an opening  115  for accommodating a positive tab  102   a  that juts out from an edge of the positive current collecting substrate  102 . According to one embodiment of the present disclosure, the outer conductive frame  105  may have a protruding negative tab  105   a . A glue layer  130  may be provided to fill the gap  125 . The glue layer  130  is flush with a covering insulation layer  132  that covers the outer conductive frame  105  and the positive current collecting substrate  102 . On the bottom surface of the negative current collecting substrate  104 , a covering insulation layer  142  may be provided. The covering insulation layers  132  and  142  may comprise polyimide (PI), polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyurethane (PU), or polyethylene terephthalate (PET), but not limited thereto. The laminated electric core  110  may be sealed by a sealant layer  122  provided along the periphery of the laminated electric core  110  between the positive current collecting substrate  102  and the negative current collecting substrate  104 . A conductor layer  124  may be provided adjacent to the sealant layer  122  by using welding, soldering, or any suitable techniques. 
     According to one embodiment of the present disclosure, the outer conductive frame  105  may be electrically coupled to the underlying negative current collecting substrate  104  through the conductor layer  124 . However, in another embodiment, the layer  124  may be composed of non-conductive materials such as an adhesive material. It is to be understood that other approaches may be used to accomplish the electrical connection between the negative current collecting substrate  104  and the outer conductive frame  105 . 
       FIG. 5A  and  FIG. 5B  show such embodiment. As shown in  FIGS. 5A and 5B , the periphery of the laminated electric core  110  between the positive current collecting substrate  102  and the negative current collecting substrate  104  is sealed by using only the sealant layer  122 . To electrically connect the negative current collecting substrate  104  with the outer conductive frame  105 , an extension portion  105   b  of the outer conductive frame  105  and an extension portion  104   b  of the negative current collecting substrate  104  may be provided. A conductive layer  126  may be applied between the extension portion  105   b  and the extension portion  104   b  to electrically connect the negative current collecting substrate  104  with the outer conductive frame  105 . 
     The shape of the battery cell as set forth in the figures is only for illustration purposes. It is not necessary that the outline of the battery cell has a rectangular shape as depicted in  FIGS. 3 and 5A . In other embodiments, the outline of the battery cell may have an irregular shape, when viewed from the above, as shown in  FIG. 8A .  FIG. 8B  shows a battery cell having an irregular shape and outline. In addition, a through opening  310  may be provided. The through opening  310  extends through the entire thickness of the battery cell. 
       FIG. 9  and  FIG. 10  illustrate another embodiment of the present invention, wherein  FIG. 10  is a cross-sectional view taken along line II-II′ of  FIG. 9 . As shown in  FIG. 9  and  FIG. 10 , the outer conductive frame  105  is a closed loop. An interconnect layer  154  is formed on the covering insulation layer  132  and is electrically connected to the positive current collecting substrate  102  through the via plug  152 . The via plug  152  may comprise conductive pastes, plated copper, solder pastes or other suitable conductive materials known in the art. The interconnect layer  154  may extend beyond the outer conductive frame  105  to form a positive connecting tab  154   a . Likewise, the outer conductive frame  105  may also extend beyond the edge of the cell to form a negative connecting tab  105   a . The positive connecting tab  154   a  and the negative connecting tab  105   a  form a battery terminal pair. 
     It is to be understood that the number of the battery terminal pair depends upon the design requirements and one battery cell may have multiple battery terminal pairs. As shown in  FIG. 11 , the battery cell comprises two battery terminal pairs  150  and  160 . The battery terminal pair  150  comprises positive connecting tab  154   a  and the negative connecting tab  105   a . Likewise, as previously described, the positive connecting tab  154   a  of the interconnect layer  154  is formed on the covering insulation layer  132  and is electrically connected to the positive current collecting substrate  102  through the via plug  152 . The battery terminal pair  160  comprises positive connecting tab  164   a  and the negative connecting tab  105   b . The positive connecting tab  164   a  of the interconnect layer  164  is formed on the covering insulation layer  132  and is electrically connected to the positive current collecting substrate  102  through the via plug  162 . In addition to the interconnect layers  154  and  164 , it is to be understood that other circuit patterns or circuit elements may also be formed on the covering insulation layer  132 . 
     The glue layer  130  is optional. For example, in  FIG. 12A , the covering insulation layer  132  directly fills into the gap  125 . In  FIG. 12B , the gap  125  is filled with the sealant layer  122  that is extruded when assembling the battery cell. In  FIG. 12C , the glue layer  130  may protrude from an upper end of the gap  125  and covers a portion of the outer conductive frame  105  and a portion of the positive current collecting substrate  102 . In  FIG. 12D , the glue layer  130  is covered by the covering insulation layer  132 . 
     According to one embodiment of the present disclosure, the lithium-ion battery  100  may have a thickness T ranging between 0.25 mm and 0.5 mm, but not limited thereto. In some cases that the battery  100  comprises folded cells, thickness may reach 2 mm. 
     The sealant layer  122 , in combination with the conductor layer  124 , satisfactorily protects the laminated electric core  110  from exposure to air or moisture. The disclosed structure provides high moisture-proof capability and insulating property. 
       FIGS. 6A-6D  show some variations of the moisture-proof and air-proof packaging structure according to some embodiments of the invention. 
     As shown in  FIG. 6A , an air gap  123  may be provided between the sealant layer  122  and the outer, peripheral conductor layer  124 . The air gap  123  may be vacuumed in one embodiment. According to another embodiment, dry air or dry inert gas may be filled into the air gap  123 . 
     Alternatively, as shown in  FIG. 6B , the peripheral ends of the current collecting substrates may be pressed together or pressed toward each other to form a tapered cross-sectional profile of the periphery of the battery cell. In this case, both of the sealant layer  122  and the conductor layer  124  have a trapezoid shaped cross section. 
     In  FIG. 6C , the conductor layer  124  is omitted. The outer conductive frame  105  and the negative current collecting substrate  104  are welded together. 
     In  FIG. 6D , the conductor layer  124  is omitted. Only the seal layer  122  is used to seal the periphery of the electric core  110 . The peripheral ends of the current collecting substrates may be pressed together or pressed toward each other to form a tapered cross-sectional profile of the periphery of the battery cell. In this case, the sealant layer  122  has a trapezoid shaped cross section. 
     The positive current collecting substrate  102  may be any one well known in the art such as an aluminum foil. The positive electrode active material layer  111  may comprise a positive electrode active substance and an adhesive, in which the positive electrode active substance may be any one known in the art for the lithium ion battery. According to some embodiments of the present disclosure, the positive electrode active substance may comprise LiCoO 2 , LiFePO 4 , LiMn 2 O 4 , or any suitable three-component substances known in the art. The adhesive may be any one well known in the art such as polyvinylidene fluoride (PVDF). According to some embodiments of the present disclosure, the positive electrode active material layer may also comprise positive electrode additives. The positive electrode additive may be any one well known in the art and may be selected from conductive agents, for example, at least one of acetylene black, conductive carbon black and conductive graphite. 
     The negative current collecting substrate  104  may be any one well known in the art such as copper foil. The negative electrode active material layer  113  may comprise a negative electrode active substance and an adhesive. The negative electrode active substance may be any one commonly used in lithium ion batteries, such as natural graphite and artificial graphite. The adhesive may be any one well known in the art such as polyvinylidene fluoride (PVDF) and polyvinyl alcohol. 
     The electrolyte may comprise a lithium salt electrolyte and solvent. In some cases, gel-type or solid state electrolytes may be used. The lithium salt electrolyte may be at least one selected from lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate (LiClO 4 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium halide, lithium aluminum tetrachloride and lithium fluoro-alkyl sulfonate. The solvent may comprise an organic solvent, such as a mixture of chain-like acid esters or cyclic acid esters. The chain-like acid ester may comprise at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), dipropyl carbonate (DPC) and other fluorine-containing, sulfur-containing or unsaturated bond-containing chain-like organic esters. Alternatively, a solid state electrolyte such as lithium phosphorus oxynitride (also known as LiPON) may be used. 
     The separator  112  is electrically insulated and also has good electrolyte retaining performance. According to some embodiments of the present disclosure, the separator may be any kind of separators used in lithium-ion batteries known in the art, such as polyolefin micro-porous membrane, polyethylene felt, glass fiber felt or ultrafine glass fiber paper. Alternatively, an adhesive resin layer (not shown) may be provided to bond the positive electrode active material layer  111  or negative electrode active material layer  113  to the separator  112 . The adhesive resin layer may have a large number of through holes that communicate the positive electrode active material layer  111  or negative electrode active material layer  113  with the separator  112 . The adhesive resin layer may create an intimate interfacial contact between adjacent layers. 
       FIG. 7  is a schematic, cross-sectional diagram illustrating a stack structure of a thin-film lithium-ion battery according to another embodiment of the invention. The stack structure of a thin-film lithium-ion battery may be composed of several secondary cells as described above in parallel to increase the discharge current capability, and may be available in series packs to increase the total available voltage. 
     As shown in  FIG. 7 , the stacked thin-film lithium-ion battery  200  may comprise at least two lithium-ion battery units  100   a  and  100   b , each of which has a structure that is similar to  FIG. 4 . For example, the upper lithium-ion battery unit  100   a  comprises a laminated electric core  110   a  comprising a positive electrode active material layer  111   a  coated on a first surface of an intermediate current collecting substrate  203 , a separator  112   a  sandwiched between the positive electrode active material layer  111   a , and a negative electrode active material layer  113   a . On the second surface of the intermediate current collecting substrate  203  is the laminated electric core  110   b  of the lower lithium-ion battery unit  100   b . The laminated electric core  110   b  comprises a positive electrode active material layer  111   b  coated on the second surface of an intermediate current collecting substrate  203 , a separator  112   b  sandwiched between the positive electrode active material layer  111   b , and a negative electrode active material layer  113   b . The laminated electric core  110   a  and the laminated electric core  110   b  are sandwiched between an upper current collecting substrate  202  and a lower current collecting substrate  204 . Likewise, sealant layers  122   a ,  122   b  and outer packaging layers  124   a ,  124   b  may be employed to provide high moisture-proof capability and insulating property. 
     The layers in the stack structure as described in  FIG. 7  may have different dimensions according to another embodiment of the invention. As shown in  FIG. 13A  and  FIG. 13B , the topmost layer  110   a  has a dimension that is smaller than the underlying layer  110   b , which is smaller than the layer  110   c , which is smaller than the layer  110   d . The layer stack forms a non-rectangular or an irregular shape, terraced structure and may have a rounder corner. By providing such non-rectangular configuration of the battery, the free space within a portable electronic device can be efficiently utilized. 
       FIG. 14A  shows a two-cell battery according to yet another embodiment. As shown in  FIG. 14A , the two cells including two laminated electric cores  110   a  and  110   b  may be arranged in parallel to each other on the negative current collecting substrate  104  and then folded to sandwich about the positive current collecting substrate  102 . The battery is then sealed by using sealant layers  122 . The two cells in  FIG. 14A  are electrically coupled in parallel.  FIG. 14B  shows a four-cell battery according to yet another embodiment. As shown in  FIG. 14B , the negative current collecting substrate  104  and the four cells including four laminated electric cores  110  are folded in a zigzag manner. The four cells in  FIG. 14B  are electrically coupled in parallel. 
       FIG. 15  illustrates the manufacturing steps for a three-cell battery pack. As shown in  FIG. 15 , an array of positive electrode active material layers  111  are formed on a panel A. An array of negative electrode active material layers  113  are formed on a panel B. On the panel A, respective electrical connection points C 0 , C 2  and C 4  are provided, which correspond to the electrical connection points C 1 , C 3  and C 5  on the panel B. The panel A is laminated onto the panel B to form a three-cell in series configuration. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.