Abstract:
A method of the present invention is used for the high-rate deposition of materials, such as carbon, silicon, metals, metal oxides, and the like, onto a metal substrate defined by a metal current collector. The particles of the material are mixed with fluid and are injected against the metal tape at high pressure and high velocity. The particles of the material form an active layer of the metal current collector. The metal current collector is used as a cathode or anode combined with a separator to form a cell of a secondary battery, metal-ceramic membranes, film composite metal-ceramic materials for electronic devices.

Description:
RELATED APPLICATIONS 
     This is a continuation-in-part application of a non-provisional patent application Ser. No. 11/560,922 filed on Nov. 17, 2006 now U.S. Pat. No. 7,717,968 which claims priority to a provisional patent application Ser. No. 60/780,240 filed on Mar. 8, 2006 and incorporated herewith in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The subject invention relates to an electrode for a cell of an electrochemical device having improved cell charged capacity, recycling stability, energy and power, method for manufacturing the same. 
     BACKGROUND OF THE INVENTION 
     The term “nanotechnology” generally refers to objects, systems, mechanisms and assemblies smaller than 100 nanometers and larger than 1 nm. In recent years nanotechnology has been used to make products, that is, raw materials are processed and manipulated until the desired product is achieved. In contrast, nanotechnology mimics nature by building a product from the ground up using a basic building block—the atom. In nanotechnology atoms are arranged to create the material needed to create other products. Additionally, nanotechnology allows for making materials stronger and lighter such as carbon nano-tube composite fibers. 
     One of the areas of continuous development and research is an area of energy conversion devices, such as for example secondary batteries capable of charging electricity after discharge and having at least one electrochemical cell. The cell includes a pair of electrodes and an electrolyte disposed between the electrodes. One of the electrodes is called a cathode wherein an active material is reduced during discharge. The other electrode is called an anode wherein another active material is oxidized during discharge. Secondary batteries refer to batteries capable of charging electricity after discharge. Recently, intensive research has been conducted on lithium secondary batteries because of their high voltage and high energy density. The typical lithium battery having an anode containing an active material for releasing lithium ions during discharge. The active material may be metallic lithium and an intercalated material being capable of incorporating lithium between layers. The active material is deposited or coated upon a metal current collector formed from a metal tape to increase electro-conductive characteristics of at least one of the electrodes. 
     Alluding to the above, various methods for deposition of the active materials onto the metal current collector have been used in the prior art applications. One of these methods is physical vapor deposition (PVD), which includes E-beam evaporation, filament evaporation and different sputtering deposition, is currently used to generate thin films on substrates, i.e. the metal current collector. However, this method includes numerous disadvantages, such as, for example, non-time effective deposition rates as relate to coating thickness of the substrate per unit, typically in the range of a few microns per minute. Another method is known as chemical vapor deposition (CVD), including rapid thermal CVD, or RT CVD, results non-time effective deposition of the coating onto the substrate. Sputtering techniques such as RF or DC sputtering, as well as laser evaporation, plasma arc evaporation, electro-spark deposition (ESD), and the like are also known to have low deposition rates. In addition, all of the aforementioned methods are performed by and require expensive vacuum equipment and do not provide strong adhesion of the coating to the substrate, which is detrimental in various applications, particularly in manufacturing electrodes for energy conversion devices, such as batteries. 
     These aforementioned methods are proven to achieve rates of tens of microns per minute. However, if the deposition rates of these methods are increased to higher rates, it may adversely impact adhesion of the coating upon the substrate. As such, these methods are limited to deposition of the coating that results in a range of 10-20 μm per minute, which has limited industrial application, such as to production of a very thin battery of the type used in electronic devices. However, these prior art methods are not cost effective when used in a production of other types of batteries, such as, for example, batteries for vehicles, and the like. 
     Alluding to the above, another method, which used vacuum, was also applied in fabrication of the substances of the electrodes. However, this method had negatively impacted the crystalline composition of the materials deposited upon the substrate. Those skilled in the art will appreciate that a shortage of oxygen in spinel phases leads to transformation of cubic crystal matrix to tetragonal one, which negatively affects electrochemical properties. The usage of carbon as a conductive agent, in some of the prior art applications, presents numerous disadvantages because of the lower electrical conductivity of the carbon as compared to metals, thereby creating additional voltage drop at the interface with the metal current collector. 
     The art is replete with various other methods and apparatuses for forming metal current collector for electrodes of a battery cell, which are disclosed in the United States Patent Publication Application Nos. 20020177032 to Suenaga; 20030203282 to Grugeon; 20040248010 to Kato et al.; and the U.S. Pat. No. 6,761,744 to Tsukamato et al. These aforementioned prior art methods share at least one disadvantage such as the active layer formed on top of the metal current collector of the electrodes to define a space therebetween, which negatively impacts cycleability and possibility to properly function in applications requiring higher C-rate. Another disadvantage of the methods mentioned above that negatively impacts both the life span of the battery and the manufacturing costs associates therewith is the structure of the battery wherein the active layer is formed on the metal current collector and additional binders used as adhesion between the active layer and the metal current collector thereby increasing both the weight and size of the battery, which, as mentioned above, negatively impacts both specific characteristics of the battery and the manufacturing costs associates therewith. 
     Alluding to the above, none of these prior art references teaches the method of forming the electrode which leads to an improved battery having the electrode with accessible porosity sufficient for penetration of electrolyte to contact with particles of the active material, conducting agent should provide contact of active substance particles with current collector. In the normal process of gas dynamic (cold spray) deposition, only metallic particles can be deposited on metallic substrate. The ceramic particles are inculcated in metal collector and do not form the necessary porosity. Introduction of a metal powder into mixture with the ceramic components leads to plastic deformation of metal particles at their collision with ceramic particles. As a result of plastic deformation metal particles create films on ceramic particles of the active substance. The resulting material does not have sufficiently accessible pore structure and is characterized by low mechanic strength. In addition, electric contact of each particle with current collector is not provided. Furthermore, at high deposition energies, metal particles can fuse during collision. In this case, conglomerates are formed. Such conglomerates disturb the uniformity of the deposited material. 
     But even with the aforementioned technique, to the extent it is effective in some respect, there is always a need for an improved processes for engineering of porous electrodes that is light, thin, cost effective, have improved cycle ability, specific energy and power as well as ability to properly function in applications that depend upon higher C-rate and easy to manufacture. 
     SUMMARY OF THE INVENTION 
     A metal current collector of the present invention is formed from a metallic tape used to form a first electrode such as an anode and a second electrode such as cathode combined into a cell for producing electric power without limiting the scope of the present invention. The metal current collector of the first electrode and the second electrode has opposed sides defining an initial thickness. An active core is formed inside the metal current collector. The active core is formed from first particles being integral with and extending from the metal current collector of at least one of the first and second electrodes and second particles formed from material other that the first particles of the metal current collector. The first and second particles connect with one another to form a porous grid of a three dimensional configuration of the active core disposed inside the metal current collector thereby resulting in the metal current collector being integral with the active core and presenting a second thickness. Based on application requirements, the second thickness may be substantially the same or smaller than the first thickness. The active core is mixed with and covered by an electrolyte. A layer of isolating bar is continuously disposed about one of the opposed sides of the metal current collector of at least one of the first and second electrodes. An anode layer is formed from lithium, carbon or other covering the active core to extend co-planarly with the layer of isolating bar. An anode current collector is formed from copper, nickel or other metal to extend over the anode layer and the layer of isolating bar. An isolating layer extends over the anode current collector sandwiched between the anode layer and the isolating layer. 
     An advantage of the present invention is to provide a unique metal current collector of an electrode with integrated active core having a porous structure received by effective deposition of an active material into the metal current collector substrate in a binder free fashion while maintaining outstanding adhesion. 
     Another advantage of the present invention is to provide a current collector wherein an active layer is formed inside the current collector thereby increasing the specific characteristics of the cell. 
     Still another advantage of the present invention is to provide a unique method for fabricating the electrodes wherein the metal current collector presents nano-structured surface at low cost. 
     Still another advantage of the present invention is to provide an electrode material having an improved nano-structure which is utilized as at least cathode or anode of a fuel cell leading to low thermal stability and improved cycling ability. 
     Still another advantage of the present invention is to provide a unique method of forming the inventive electrode structure for the cell by virtue of a unique high-pressure deposition solidification method wherein the particles of active material and solidified drops formed as a result of formation of aerosol mixture form a grid presenting a continuous surface of the metal current collector of the electrode. 
     Still another advantage of the present invention is to provide the metal current collector for the electrode presenting stable operation in a broad range of discharge rates and operating temperatures. 
     Still another advantage of the present invention is to provide high-performance equipment and methodology for high speed deposition of the particle of the active material while suppressing it&#39;s possible thermo-chemical degradation. 
     The present inventive concept has various applications including and not limited to high efficiency thin-film photovoltaic solar cells for cost-effective renewable energy, fuel cell components such as catalytic membranes for environmentally friendly power supplies, super capacitors for smaller and lighter portable handheld devices such as cell phones, laptops, thin film sensors for more effective monitoring and control of temperature, illumination, and humidity, high-conductivity wires with low resistance adaptable for manufacturing of a wide variety of electronic devices, and the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1A  illustrates cross sectional view of a structure on an inventive metal current collector for electrodes of opposite polarity wherein particles of an active material are represented by crystals or amorphous particles interconnected with a multitude of other particles of circular shape representing accreted and crystallized drops of melted metal current collector; 
         FIG. 1B  illustrates a perspective view of the structure of the metal current collector of an electrode of  FIG. 1A ; 
         FIG. 2A  illustrates is a perspective and segmental view of the metal current collector of the electrode and the first particles colliding therewith thereby melting the metal current collector with some particles partially entering the metal current collector; 
         FIG. 2B  is a partially cross sectional view of the electrode having the metal current collector of  FIG. 2A ; 
         FIG. 2C  illustrates is a perspective and segmental view of the metal current collector and the first particles disposed inside the metal current collector with the areas of local melting of current collector shown in phantom; 
         FIG. 2D  is a partially cross sectional view of the metal current collector of  FIG. 2C  with the first particles shown in phantom; 
         FIG. 2E  illustrates is a perspective and segmental view of the metal current collector and the metal drops splashed from the metal current collector as in response to the impact of the first particles against the metal current collector and applying ultrasonic vibration; 
         FIG. 2F  is a partially cross sectional view of the electrode of  FIG. 2E ; 
         FIG. 2G  illustrates is a perspective and segmental view of the metal current collector and the metal drops solidified in the shaped of the second particles and interconnected with the first particles to form a grid of a porous structure of an active core inside the metal current collector; 
         FIG. 2H  is a partially cross sectional view of the metal current collector of  FIG. 2G ; 
         FIG. 3A  illustrates a perspective view of an apparatus for forming the electrode having the metal current collector disposed therein; 
         FIG. 3B  illustrated a fragmental view of the apparatus shown in  FIG. 3A ; 
         FIGS. 4A through 4E  illustrate various cross sectional view of the metal current collector of the present invention as the metal current collector is moved along an assembly path with the active core being formed inside the metal current collector; 
         FIG. 5  shows a schematic vie of the assembly of the cell by combining the electrodes of opposite polarity with each electrode having inventive active core inside the current collector; 
         FIG. 6A  illustrate various microscopic views of fracture of the inventive electrode to clearly illustrate the first and second nano-particles of the active core with each of the particles having nano-dimensions; 
         FIG. 6B  illustrate the cross section structure of initial aluminum current collector before the active material deposition; 
         FIG. 6C  illustrate the cross section structure of the electrode with the active layer deposited inside current collector shown in the  FIG. 6B ; 
         FIG. 7  presents a graph illustrating electrochemical testing results of the cell having a cathode electrode formed according to the present invention; 
         FIG. 8A  is a perspective view of at least one configuration of the inventive cell; 
         FIGS. 8B and 8C  show a microscopic views of the cross section of the thin cell with at least one electrode formed according to present invention; and 
         FIG. 9  presents another graph illustrating electrochemical testing results of the cell having at least one electrode formed according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the Figures, wherein like numerals indicate like or corresponding parts, an electrode of the present invention is generally shown at  10 . The electrode  10  of the present invention is formed from a metallic tape, generally indicated at  11  and shown fragmentally in  FIGS. 1A to 2H , is used to form a first electrode such as an anode and a second electrode such as cathode, both illustrated at A and C, respectively, in  FIGS. 5 and 8B  and  8 C, and spaced by a separator S and combined into a cell, generally indicated at  13  in  FIG. 8A , for producing electric power without limiting the scope of the present invention. The metal current collector  11  of the first electrode and the second electrode has opposed sides  12  and  14  defining an initial thickness  16 , as best illustrated in a cross sectional view shown in  FIG. 1A . An active core, generally shown at  18  in  FIG. 1A , is formed inside the metal current collector  10 . The active core  18  is formed from first particles  20  being integral with and extending from the metal current collector  11  of at least one of the first and second electrodes. The first particles  20  are formed as the second particle  22 , impacting the metal current collector  11 , as best shown in  FIGS. 2A and 2B , resulting in local increased temperature of the metal current collector  11 , which locally melts, as shown in  FIGS. 2C and 2D , as the second particles  22  are at least partially penetrate the metal current collector  11 . As best illustrated in  FIGS. 2E and 2F , the impact of the second particles  22  onto the melted metal current collector  11  results in multitude of aerosol drops  24  separated from the metal current collector  11 , as best illustrated in  FIGS. 2E and 2F . The active core  18  is formed in response to solidification of the aerosol drops  24 , which follows local melting and ultrasonic cavitations of the metal current collector  11  thereby forming the first particles  20 . The first particles  20  are integral with the metal current collector and present circular or globular configuration, as view in a cross section. The second particles are formed from of active material, other that the metal current collector  11 , and may present a rectangular configuration, or other configuration, and the like, as best shown in  FIGS. 1A and 1B , without limiting the scope of the present invention. The circular configuration of the second particles  22 , as shown in  FIGS. 2A through 2H  are for illustrative purposes only without intent to limit the scope of the present invention. the active material of the second particles  22  includes and not limited to silicon, carbon, germanium, oxides, salts, ceramic components, LiCoO 2 , LiMn 2 O 4 , LiFePO 4 , MnO 2 , Li, Si, C, Ge, SnO, SnO 2 , and the like, without limiting the scope of the present invention. 
     The first and second particles  20  and  22  are connected with one another to form a porous grid, generally indicated at  32  in  FIGS. 1A and 1B  of a three dimensional configuration of the active core  18  disposed inside the metal current collector  11  thereby resulting in the metal current collector  11  being integral with the active core  18  and presenting a second thickness  34 . The grid  32  is further defined by the first particles  20  being continuously connected with the metal current collector  11  thereby eliminating sharp interface between the grid  32  and the metal current collector  11 . The first particles  20  are connected to the second particles  22  and the metal current collector  11  in a diffusible fashion with the second particles  22  being at least partially exposed through and beyond the grid  32 . Alternatively, the second particles  22  are inside the grid  32  of the active core  18  and do not exposed beyond the active core  18 . The first particles  20  and the second particles  22  are free from low conductivity films at interface defined between the first and second particles  20  and  22  and the metal current collector  11 . The first particles  20  are fused with one and the other thereby forming an inter-layered structure of the grid  32  with the second particles  22  disposed therebetween. The second particles  22  and the metal current collector  11  define points of contacts having a thermal decomposition temperature being lower than a melting temperature of the first particles  20 . The second particles  22  present a size ranging from at least 50 nm and up to 500 nm. The first particles  20  present a size ranging from at least 5 nm and up to 100 nm. 
     Based on application requirements, the second thickness  34  may be substantially the same or smaller than the first thickness  16 . The grid  32  presents a plurality of pores, only some of the pores are shown at  36  in  FIG. 1A . The grid  32  may present 60 percent of the pores  36  and 40 percent of the first and second particles  20  and  22  of a total volume of the active core  18 . This ratio is not intended to limit the scope of the present invention. The pores  36  may present up to 80 percent of the active core  18  or only 0.55 percent of the active core  18 . This ratio is not intended to limit the scope of the present invention. The active core  18  is mixed with and covered by an electrolyte, as best shown at  38  in  FIG. 4C . The electrolyte  38  may be liquid or non-liquid. 
     Alluding to the above, one of the advantages of the present invention is the absence of an oxide film at contact points the first and second particles  20  and  22 , which reduces electronic resistance at the interface of the cathode&#39;s C active substance and metal binding. Multitude of contact points defined between the particles  20  and  22  and the metal current collector  11  expose the greater part of the active core  18  open to electrochemical interaction with the electrolyte. The size of the first particles  20  as viewed in cross section is between 5 to 100 nm. The size of the second particles  22  formed from the active substance is between 50 to 500 nm. Based on the results conducted by the applicant through a quantitative electron-microscopic inspection, the average number of contacts of the metal, i.e. the first particles  20  and the metal current collector  10  with the second particles  22  of the active material is 25-32 per square micron of particle surface, thereby providing reliable and improved outlet of electrons to the metal current collector  10  during cyclic changes in active substance particle size during reversible electrode operation in the cell  13 . In some applications of the present invention the three-dimensional grid  32  has low thickness and the second particles  22  of form the dense one layer film on the electrode surface. 
       FIGS. 3A and 3B  illustrate fragmental view of the inventive apparatus  40  of the present invention, which is described in great details in the patent application serial number incorporated herewith in its entirety.  FIGS. 3A and 3B  illustrate a nozzle  42  through which the second particles  22  of the active material are injected onto the tape  44  of the electrode  10  rolled between a pair of rollers  46  and  48 . An ultrasonic vibrator, generally shown at  45  in  FIGS. 3A and 3B , is positioned to abut the inner side of the tape  44 . The functional aspects and purpose of the ultrasonic vibrator  45  are disclosed in the patent application Ser. No. 11/560,922 incorporated herewith by reference in its entirety. A brush  50  is positioned adjacent the tape  44  to extract excess of the first and second particles  20  and  22 .  FIGS. 4A through 4E  illustrate various cross sectional view of the electrode  10  of the present invention as the metal current collector  11  is moved along an assembly path with the active core  18  being formed inside the metal current collector  11 . As the active core  18  is formed inside the metal current collector  11 , as described above, and is filled and/or mixed with the electrolyte  38 , a layer of isolating bar  60  is continuously disposed about one of the opposed sides  12  of the electrode  10  of at least one of the first and second electrodes. In one embodiment, the electrode  10  can be an anode and can also include an anode layer  62  formed from lithium covering the active core  18  to extend co-planarly with the layer of isolating bar  60 . In such an embodiment, an anode current collector  64  formed from copper, nickel or other metal can extend over the anode layer  62  and the layer of the isolating bar  60 . An isolating layer  66  extends over the anode current collector  64  sandwiched between the anode layer  62  and the isolating layer  66 . The structure of the electrode  10  as set forth above is applicable to both the anode A and the cathode C of the present invention.  FIGS. 8B and 8C  illustrate a cross section of the cell includes the anode A and the cathode C formed by the method of the present invention, clearly illustrating the dimensions of the anode A of 15 μm, the cathode of 9 μm, and the separator S of 10 μm. The table shown further below illustrates dimensions and technical characteristics of the preferred embodiment of the cell  13  of the present invention. However, these dimensions are illustrated for exemplary purposes as one of the embodiment of the present invention and are not intended to limit the scope of the present invention. 
     
       
         
               
               
               
             
           
               
                   
               
             
             
               
                 Cathode - Al current collector 
                 Thickness, μm 
                 9 
               
               
                 with active substance LiMn2O4 
                 Δm, mg/cm 2   
                 0.7-0.9 
               
               
                 Separator + polymer electrolyte 
                 Thickness, μm 
                 10-16 
               
               
                 Anode - Cu current collector with Li 
                 Thickness, μm 
                 15 
               
               
                 Total of battery 
                 Expectancy 
                 40 
               
               
                   
                 Thickness, μm 
                   
               
               
                   
                 Real Thickness, μm 
                 50 
               
               
                   
                 See Ris. 2. 
                   
               
               
                   
                 Capacity, mAh/cm2 
                 0.07-0.09 
               
               
                   
                 at low current 
                   
               
               
                   
                 Volume, cm 3   
                 0.01 
               
               
                   
                 Capacity, mAh at 
                 0.18 
               
               
                   
                 low current 
                   
               
               
                   
                 discharge 
                   
               
               
                   
                 Average voltage, 
                 3.9 
               
               
                   
                 V at low current 
                   
               
               
                   
                 discharge 
                   
               
               
                   
                 Energy density Wh/l 
                 70 
               
               
                   
                 Peak Power W/l 
                 &gt;500 
               
               
                   
               
             
          
         
       
     
     As best illustrated in  FIG. 5  an assembly “roll to roll” process of the present invention is generally shown at  68 . The cathode C and the anode A are rolled from two spaced drums  70  and  72  along an assembly path  74  with the metal current collector  10  of each of the cathode C and the anode A facing one another. An electrolyte with separator (if necessary)  76 , either liquid or non-liquid is injected between the cathode C and the anode A in addition to the electrolyte  38  of the metal current collector  10 . A heating element (not shown) is adjacent the assembly path  74  to heat the electrolyte  76  thereby improving polymerization of the electrolyte  76 . After the cathode c and the anode A are sealed  80  a pair of cutting devices  82  and  84  disposed on both sides of the assembly path  74  are cutting the assembled cathode C and the anode A to a multitude of prefabricated cells  13 . Numerous mechanical, laser, and electrical devices are used as cutting devices  82  and  84  and are not intended to limit the scope of the present invention. The cells  13  are sealed hermetically along the peripheral edge or the periphery  86 . 
       FIGS. 6A through 6C  illustrate various cross section microscopic views to clearly illustrate the first and second nano-particles  20  and  22  of the active core  18  with each of the particles having nano-dimensions.  FIG. 7  presents a graph illustrating electrochemical testing results of cathode electrode  10  formed according to the invention.  FIG. 8A  is a perspective view of at least one configuration of the inventive cell.  FIGS. 8B and 8C  show cross section microscopic views of the electrodes of opposite polarity with at least one electrode formed according to the invention.  FIG. 9  presents another graph illustrating electrochemical testing results of the cell shown in the  FIGS. 8  A-C having at least one electrode made according to the present invention. 
     Alluding to the above, the electrode  10  and the method of forming the same have numerous valuable advantages of the prior art electrodes and methods. One of the advantages, for example, is the unique structure of the electrode  10  wherein the active core  18  is formed in an organic binder free fashion, i.e. by the inventive method of solidification of the aerosol drops  24  of the metal current collector  10  and the particles  22  of active material while maintaining adhesion therebetween. Another advantage of the present invention is to provide a unique method for fabricating the electrodes A and/or C wherein the metal current collector  10  presents nano-structured surface, has low thermal stability and improved cycling life. The unique method of forming the electrodes A and/or C utilizes the high-pressure deposition solidification method wherein the particles  22  of the active material and the solidified drops  24  are formed as a result of the formation of the aerosol mixture form the grid  32  presenting a continuous surface of the metal current collector  10  of the electrodes A and/or C. The present inventive concept has various applications including and not limited to high efficiency thin-film photovoltaic solar cells for cost-effective renewable energy, fuel cell components such as catalytic membranes for environmentally friendly power supplies, super capacitors for smaller and lighter portable handheld devices such as cell phones, laptops, thin film sensors for more effective monitoring and control of temperature, illumination, and humidity, high-conductivity wires with low resistance adaptable for manufacturing of a wide variety of electronic devices, and the like. 
     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.