Abstract:
A drop-fill assembly and method for uniformly distributing electrode active particles onto a current collector is described. The drop-fill assembly comprises a conduit containing two or more spaced apart sifting screens. A funnel is located upstream of the sifting screens to distribute an electrode active powder into the center of the conduit with a downward velocity. The mesh of any one sifting screen is out of direct alignment with respect to the next or previous screen. The electrode active powder is poured into the funnel and distributed across the conduit&#39;s cross-section as it bounces off and passes through the misaligned sifting screens. The powder exits at the bottom of the conduit lying in a thin, uniform layer on a current collector, taking on the shape of the desired electrode due to the boundary of the conduit and pressing fixtures located above and beneath the current collector. The powder layer is then pressed on to the current collector to produce an electrode.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from provisional application Ser. No. 60/417,329, filed Oct. 9, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to the conversion of chemical energy to electrical energy. More particularly, the invention relates to the manufacture of electrode active structures, such as cathode electrodes, for incorporation into electrochemical cells. In building a cathode, particularly one made from a granular material, it is important that the active material is of a uniform thickness and packing density supported on the opposed contact surfaces of the intermediate current collector. Having a uniform layer of active material contacting each side of the current collector promotes improved electrical performance, especially as end-of-life (EOL) cell discharge approaches. Exemplary cathode active materials are silver vanadium oxide (SVO) and fluorinated carbon (CF x ). 
     The present invention is also applicable to anode electrodes, particularly those used in secondary or rechargeable cells where a granular active material is the anode active material. An exemplary anode material is of a granular carbonaceous material. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a drop-fill assembly and method for uniformly distributing electrode active particles onto a current collector. The drop-fill assembly comprises a conduit containing two or more spaced apart sifting screens. A funnel is located upstream of the sifting screens to distribute an electrode active powder into the center of the conduit with a downward velocity. The mesh of any one sifting screen is out of direct alignment with respect to the next or previous screen. The electrode active powder is poured into the funnel and distributed across the conduit&#39;s cross-section as it bounces off and passes through the misaligned sifting screens. The powder exits at the bottom of the conduit lying in a thin, uniform layer on a current collector, taking on the shape of the desired electrode due to the boundary of the conduit and pressing fixtures located above and beneath the current collector. A deionizer is typically used to prevent static. The powder layer is then pressed on to the current collector to produce an electrode. 
     These and other aspects of the present invention will become more apparent to those skilled in the art by reference to the following description and to the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is an exploded view of the upper parts of the present drop-fill assembly  10  according to the present invention and a pressing fixture assembly  12 . 
     FIG. 1B is an exploded view of the lower parts of the drop-fill assembly  10 . 
     FIG. 2 is a partial cross-sectional view of the pressing fixture assembly  12  used in conjunction with the drop fill assembly  10 . 
     FIG. 3 is a plan view of exemplary shapes for electrodes that are producible with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, FIGS. 1A and 1B are exploded views illustrating the main components or parts of a drop-fill assembly  10  according to the present invention. FIG. 2 illustrates the pressing fixture assembly  12  used in conjunction with the drop fill assembly. The drop-fill assembly  10  is a conduit-shaped structure supported on the pressing fixture assembly  12  and comprises a first block  14 , a second block  16 , a third block  18 , a fourth block  20  and a fifth or upper block  22 . Sifting screens  24 A and  24 B are captured between the first and second blocks  14 ,  16 . Sifting screens  26 A and  26 B are captured between the second and third blocks  16 ,  18 . And, sifting screens  28 A and  28 B are captured between the third and fourth blocks  18 ,  20 . 
     The blocks  14 ,  16 ,  18 ,  20 , and  22  are made of a polymeric material, such as of acrylics or PLEXIGLAS®, and the like. In any event, the polymeric material must not contaminate the active material during use. 
     The first block  14  is a rectangular shaped member comprising spaced apart right and left sidewalls  30 A and  30 B extending to front and back sidewalls  30 C and  30 D. These sidewalls extend to upper and lower parallel planar surfaces  32  and  34 . Openings  36  and  38  are provided through the thickness of the first block  14  extending from the upper surface  32  to the lower surface  34 . Recesses  40  and  42  are provided in the upper surface surrounding the respective openings  36 ,  38 . 
     A through bore  44  extends from the upper surface  32  to the lower surface  34 , intermediate the right wall  30 A and the right recess  40 . Similarly, a through bore  46  extends from the upper surface  32  to the lower surface  34 , intermediate the left wall  30 B and the left recess  42 . Finally, pins  48  and  50  are provided in the first block  14 . They are aligned with their longitudinal axes parallel to those of the respective through bores  44 ,  46 . However, the lower portion of each pin  48 ,  50  protrude below the lower surface  34  of the block. As will be described hereinbelow, pins  48 ,  50  are for positioning the drop-fill assembly  10  supported on the pressing-fixture assembly  12 . The right and left recesses  40 ,  42  are sized to receive the sifting screens  24 A and  24 B, respectively. 
     The second block  16  is a rectangular shaped member comprising spaced apart right and left sidewalls  52 A and  52 B extending to front and back sidewalls  52 C and  52 D. These sidewalls extend to parallel upper and lower planar surfaces  54  and  56 . Openings  58  and  60  are provided through the thickness of the block  16  extending from the upper surface  54  to the lower surface  56 . Respective recesses  62  and  64  surround the openings  58 ,  60 . 
     Respective through bores  66  and  68  extend from the upper surface  54  to the lower surface  56  adjacent to the right and left openings  58 ,  60  and associated recesses  62 ,  64 . When the second block  16  is positioned on the first block  14 , the through bores  66 ,  68  are aligned with the bores  44 ,  46  in block  14 . Also, the sifting screens  24 A and  24 B are positioned between the lower surface  56  of the second block  16  and the first block  14 , captured in recesses  40 ,  42 . With the second block  16  supported on the first block  14 , the upper ends of the pins  48 ,  50  are exposed. 
     The third block  18  is a rectangular shaped member comprising spaced apart right and left sidewalls  70 A and  70 B extending to front and back sidewalls  70 C and  70 D. These sidewalls extend to parallel upper and lower planar surfaces  72  and  74 . Openings  76  and  78  are provided through the thickness of the block  18  extending from the upper surface  72  to the lower surface  74 . Respective recesses  80  and  82  surround the openings  76 ,  78 . 
     Through bores  84  and  86  extend from the upper surface  72  to the lower surface  74  adjacent to the right and left openings  76 ,  78  and associated recesses  80 ,  82 , respectively. When the third block  18  is positioned on the second block  16 , the through bores  84 ,  86  are aligned with the bores  66 ,  68  in block  16 . The sifting screens  26 A and  26 B are positioned between the lower surface  74  of the third block  18  and the second block  16 , captured in recesses  62 ,  64 . 
     The fourth block  20  is a rectangular shaped member comprising spaced apart right and left sidewalls  88 A and  88 B extending to front and back sidewalls  88 C and  88 D. These sidewalls extend to parallel upper and lower planar surfaces  90  and  92 . Openings  94  and  96  are provided through the thickness of the block  20  extending from the upper surface  90  to the lower surface  92 . 
     Through bores  98  and  100  extend from the upper surface  90  to the lower surface  92  adjacent to the right and left openings  94 ,  96 , respectively. When the fourth block  20  is positioned on the third block, the through bores  98 ,  100  are aligned with the bores  84 ,  86  in block  18 . The sifting screens  28 A and  28 B are positioned between the lower surface  92  of the fourth block  20  and the third block  18 , captured in recesses  80 ,  82 . 
     The fifth upper block  22  is a rectangular shaped member comprising spaced apart right and left sidewalls  102 A and  102 B extending to front and back sidewalls  102 C and  102 D. These sidewalls extend to parallel upper and lower planar surfaces  104  and  106 . Funnel shaped openings  108  and  110  are provided through the thickness of the block  20 . The funnels  108 ,  110  have first frusto-conical openings  108 A,  110 A leading from the upper surface  104  to respective second frusto-conical openings  108 B,  110 B exiting at the lower surface. 
     Respective through bores  112  and  114  extend from the upper surface  104  to the lower surface  106  adjacent to the right and left funnels  108 ,  110 . When the fifth block  22  is positioned on the fourth block, the through bores  112 ,  114  are aligned with the bores  98 ,  100  in block  20 . 
     The first, second, third, fourth and fifth blocks  14 ,  16 ,  18 ,  20  and  22  preferably each have a height as measured from their respective upper surfaces to their lower surfaces of about one inch to about three inches. In that respect, the drop-fill assembly  10  can have its various block  14 ,  16 ,  18 ,  20  and  22  of various heights as either unitary members or, there can be spacer blocks inserted into the column to add more height. The spacer blocks would not necessarily both support and capture a sifting screen, but are provided to add height to the overall assembly. This may be necessary, for example, when different active materials are being processed. One active material may require a higher fall height to the current collector than another to provide the desired uniform thickness layer on the opposite sides of the current collector. 
     An elongated bolt  116  extends through the aligned through bores  44 ,  66 ,  84 ,  98  and  112  in the respective blocks  14 ,  16 ,  18 ,  20  and  22 . The bolt  116  has an enlarged head that nests in a recess in the lower surface  34  of the first block  14 . A threaded portion of the bolt extends above the upper surface  104  of the fifth block  22  and receives a nut  118 . Similarly, an elongated bolt  120  extends through the aligned bores  46 ,  68 ,  86 ,  100  and  114  in respective blocks  14 ,  16 ,  18 ,  20  and  22 . An enlarged head of the bolt  120  nests in a recess in the first block lower surface. A threaded portion of the bolt extends above the upper surface  104  of the fifth block  22  and receives a nut  122 . That way, the bolts  116  and  120  secure the blocks  14 ,  16 ,  18 ,  20  and  22  together with the sifting screen pairs  24 A,  24 B,  26 A,  26 B,  28 A and  28 B captured in their respective recesses. 
     The pressing fixture assembly  12  comprises a lower pressing fixture plate  124  and an upper pressing fixture plate  126 . As shown in FIG. 2, the upper fixture plate  126  is supported on the lower fixture plate  124  by vertically oriented guide pins  127  and  128 . The guide pins  127 ,  128  are press fit into openings in the lower fixture plate  124  and prevent relative lateral movement between the fixture plates  124 ,  126  while allowing the upper plate to be slipped off of the lower plate. Threaded members  130  and  132  are received in machined grooves in the guide pins  127 ,  128  to provide additional retaining structure. That way, the upper pressing fixture  126  is in a slip-fit relationship with the lower pressing fixture  124  for positioning a current collector (not shown) there between prior to the drop fill assembly  10  being supported on the pressing fixture assembly  12 . As will be described in detail hereinafter, openings  134  and  136  in the upper pressing fixture plate  126  and openings  138  and  140  in the lower pressing fixture plate  124  receive an electrode active material after it has fallen through the drop-fill assembly  10 . Then, the drop-fill assembly  10  is removed from the pressing fixture assembly  12  and upper plugs  142  and  144  are fitted in the respective openings  134 ,  136  before the pressing fixture assembly is moved to a press for producing the product electrodes. 
     The upper pressing fixture  126  has a generally rectangular cross-section comprising spaced apart right and left sidewalls  126 A and  126 D extending to and meeting with front and back walls  126 C and  126 D. These side walls extend to an upper surface  148  and a lower surface  150  (FIG. 3) providing the upper pressing fixture plate with a thickness dictated by the height of the walls. 
     The opening pairs  134 ,  136  and  138 ,  140  are of a similar shape, although that is not necessary. However, the shape of the openings dictate the shape of the product electrode. In FIG. 1B, the openings  134 ,  136  are of a generally square cross-sectional shape in plan view to provide a similarly configured product electrodes. FIG. 3 shows other exemplary electrode shapes for the openings in the lower and upper pressing fixture plates  124 ,  126 . Those include generally rectangular with a radiused edge  150 , elongated generally rectangular with two radiused edges  152 , generally rectangular with curved sides  154  and  156  of different radii, and generally rectangular with curved edges  158 . Those skilled in the art will understand that the openings can have a myriad of other shapes, only limited by the configuration of a cell into which the resulting electrode is to be used. 
     Bevels  160 A and  160 B surround the side-by-side openings  134 ,  136 . The bevels help funnel the electrode active material into the openings  134 ,  136  centered substantially at an equal distance between the right and left sidewalls  126 A,  126 B and the front and back sidewalls  126 C,  126 D of the upper pressing fixture plate  126 . 
     The lower pressing fixture plate  124  is somewhat larger than the upper pressing fixture plate  126  in rectangular cross-section and comprises spaced apart right and left sidewalls  124 A and  124 B extending to and meeting with front and back walls  124 C and  124 D. These sidewalls extend to an upper surface  162  and a lower surface  164  providing the fixture plate with a thickness between the surfaces. 
     As shown in FIG. 2, the pressing fixture assembly  12  includes a set-up cradle  166  that supports the lower pressing fixture plate  124 . The cradle  166  comprises a base plate  168  having threaded openings  170 A,  170 B in its opposed sides. The openings  170 A,  170 B receive screws  172 ,  174 . Upstanding legs  176  and  178  are movably secured to the base plate  168  by the screws  172 ,  174 . While not shown in the drawing, the legs are provided with grooves so that upon loosening the screws, the base plate is vertically adjustable relative to the legs. 
     A spacer plate  180  rests on top of the base plate  168  and is vertically movable up and down relative to the legs  176 ,  178  along with the base plate. The lower surface of the lower pressing fixture plate  124  has a cut-out  182  centered in communication with the openings  138 ,  140 . An adjusting plate  184  is nested in the cut-out  182 . The adjusting plate  184  supports lower plugs  186  and  188  housed in respective openings  138 ,  140  on the lower pressing fixture plate  124 . The height of the adjusting plate  184  together with the height of the lower plugs  186 ,  188  is substantially equal to the depth of the openings  138 ,  140 . That way, when the screws  172 ,  174  are loosened and base plate  168  is moved relative to the legs  176 ,  178 , the spacer plate  180 , adjusting plate  184  and supported plugs  186 ,  188  are moved relative to the upper surface  162  of the lower pressing fixture plate  124 . This movement is used to regulate the resulting amount of electrode active material that fills in below the current collector (not shown) captured between the pressing fixture plates  124 ,  126 . 
     In use, an active material in a particulate form is loaded into the funnels  108 ,  110 . The funnels are sized so that about 0.1 cc/sec. to about 1.0 cc/sec., more preferably about 0.3 cc/sec. to about 0.5 cc/sec., of active material exits the second frusto-conical openings  108 B,  110 B. That way, the funnels serve to meter the rate of descent of the active particles through the assembly  10 . 
     The active material from the funnels first falls through the openings  94 ,  96  in the fourth block  20  and impinges on the screens  28 A,  28 B. As the active material bounces off of and passes through the screens, it tends to substantially occupy the entire area of the openings  76 ,  78  in block  18  below the screens. 
     The active material continues its free fall through the openings  76 ,  78  in third block  18  to then impinge on sifting screens  26 A,  26 B. An important aspect of the present invention is that the mesh of the sifting screens  26 A,  26 B is oriented at from about a 10° to about an 80° angle, more preferably at about a 45° angle out of direct alignment, with respect to the mesh of the upper sifting screens  28 A,  28 B. That is, each of the screen  28 A,  28   b  comprises warp and weft strands that are aligned at about 90° with respect to each other. Then, the warp and weft strands of sifting screens  26 A,  26 B are preferably aligned at about a 45° angle with respect to the warp and weft strands of screens  28 A,  28 B. This pattern is continued throughout the entire assembly so that the orientations of the warp and weft strands of any one sifting screen are angled with respect to those of the sifting screens immediately above and below it. 
     The active material continues its free fall through the screens  26 A,  26 B and the openings  58 ,  60  of the second block  16  where they once again impinge upon sifting screens  24 A,  24 B. Again, these screens are angled at from about a 10° to about an 80°, more preferably at about a 45° angle, with respect to the mesh of the screens  26 A,  26 B above them. By now, the free falling active material substantially occupies the entire area of the openings  36 ,  38  in a uniform distribution pattern as it falls through the first block  14 . 
     Previously, electrode current collectors have been captured between the lower and upper pressing fixture plates  124 ,  126  centered with respect to the respective right and left opening pairs  134 ,  138  and  136 ,  140 . The current collectors can be screens, perforated foils or of an expanded mesh. In any event, the current collectors have from about 2% to about 80% open area, more preferably form about 40% to about 75% open area. This is sufficient to allow some of the active material to fall through the current collectors and fill in the open area above the lower plugs  186 ,  188  in the lower pressing fixture plates  124 . The remaining active material accumulates in the openings  134 ,  136  above the current collectors. 
     In an alternate embodiment, about one-half of the active material needed for an electrode is first loaded into the open area of the openings above the lower plugs before the current collectors are captured between the pressing fixture plate  124 ,  126 . This is generally going to be the case for current collectors that are not perforated or that do not have a sufficient amount of open area to ensure a sufficient amount of active material is pressed onto the lower side of the current collector. 
     Then, the drop-fill assembly is supported on the pressing fixture assembly  12  with the pegs  48 ,  50  received in the respective openings  190 ,  192 . This serves to position the various blocks  14 ,  16 ,  18 ,  20  and  22  and the associated sifting screen pairs aligned with the current collectors. The remaining one-half of the required active material for the electrode build is loaded into the funnels  108 ,  110  and allowed to fall through the blocks and sifting screens to cover the other side of the current collectors with a uniform thickness layer having a generally even particle size distribution. 
     While not shown in the drawings, after the active material is filled onto the opposite sides of the current collectors as uniform thickness layers, the drop fill assembly  10  is removed from the pressing fixture assembly  12 . Plugs  142  and  144  are inserted into the respective openings  134 ,  136 , and the pressing fixture assembly  12  is moved to a press. The press subjects the active material to a force of about one ton to about 150 tons to press contact the active material to the opposite sides of the current collectors. For example, SVO is typically pressed at a force of about 16 to 150 tons while CF x  is pressed at about one to 10 tons. That way, the pressing force serves to lock the active material together through the openings in the intermediate current collectors. 
     While the present drop-fill assembly  10  has been described as having three pairs of sifting screens, that is not necessary. Instead, there can be two pairs or more than three pairs of sifting screen in the assembly. Also, the sifting screens and associated block openings need not be provided as side-by-side pairs. The present assembly  10  can have a single opening in each block, or there can be more than two openings provided in a readily usable pattern. 
     As previously described, a deionizer device can be used with the drop-fill assembly  10  to prevent static charges from building up as the active material falls through the tower of blocks and sifting screens. Also, it may be desirable to have a vibration device (not shown) associated with the assembly. This would help ensure that the active material does not accumulate at a sifting screen, which could eventually clog the assembly. A vibration device would also help provide a uniform layer of active material on the current collector. 
     The drop-fill assembly  10  of the present invention is useful for constructing cells of either a primary chemistry or a secondary, rechargeable chemistry. For both the primary and secondary types, the cell comprises an anode active metal selected from Groups IA, IIA and IIIB of the Periodic Table of the Elements, including lithium, sodium, potassium, etc., and their alloys and intermetallic compounds including, for example, Li—Si, Li—Al, Li—B and Li—Si—B alloys and intermetallic compounds. The preferred metal comprises lithium. An alternate negative electrode comprises a lithium alloy, such as lithium-aluminum alloy. The greater the amounts of aluminum present by weight in the alloy, however, the lower the energy density of the cell. 
     For a primary cell, the anode is a thin metal sheet or foil of the lithium material, pressed or rolled on a metallic anode current collector, i.e., preferably comprising nickel, to form the negative electrode. In the exemplary cell of the present invention, the negative electrode has an extended tab or lead of the same material as the current collector, i.e., preferably nickel, integrally formed therewith such as by welding and contacted by a weld to a cell case of conductive material in a case-negative electrical configuration. Alternatively, the negative electrode may be formed in some other geometry, such as a bobbin shape, cylinder or pellet to allow an alternate low surface cell design. 
     In secondary electrochemical systems, the anode or negative electrode comprises an anode material capable of intercalating and de-intercalating the anode active material, such as the preferred alkali metal lithium. A carbonaceous negative electrode comprising any of the various forms of carbon (e.g., coke, graphite, acetylene black, carbon black, glassy carbon, etc.) that are capable of reversibly retaining the lithium species is preferred for the anode material. A “hairy carbon” material is particularly preferred due to its relatively high lithium-retention capacity. “Hairy carbon” is a material described in U.S. Pat. No. 5,443,928 to Takeuchi et al. This patent is assigned to the assignee of the present invention and incorporated herein by reference. Graphite is another preferred material. Regardless of the form of the carbon, fibers of the carbonaceous material are particularly advantageous because they have excellent mechanical properties that permit them to be fabricated into rigid electrodes that are capable of withstanding degradation during repeated charge/discharge cycling. Moreover, the high surface area of carbon fibers allows for rapid charge/discharge rates. 
     A typical negative electrode for a secondary cell is fabricated by mixing about 90 to 97 weight percent “hairy carbon” or graphite with about 3 to 10 weight percent of a binder material, which is preferably a fluoro-resin powder such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylenetetrafluoroethylene (ETFE), polyamides, polyimides, and mixtures thereof. This negative electrode admixture is provided on a current collector such as of a nickel, stainless steel, or copper foil or screen by the drop-fill assembly  10  of the present invention or by casting, pressing, rolling or otherwise contacting the admixture thereto. 
     By way of illustration, and in no way intended to be limiting, exemplary cathode active materials comprise silver vanadium oxide having the general formula Ag x V 2 O y  (SVO) in any one of its many phases, i.e. β-phase silver vanadium oxide having x=0.35 and y=5.18, γ-phase silver vanadium oxide having x=0.80 and y=5.4 and ε-phase silver vanadium oxide having x=1.0 and y=5.5, and combination and mixtures of phases thereof. For a more detailed description of silver vanadium oxide materials, reference is made to U.S. Pat. No. 4,310,609 to Liang et al., U.S. Pat. No. 5,389,472 to Takeuchi et al., U.S. Pat. No. 5,498,494 to Takeuchi et al. and U.S. Pat. No. 5,695,892 to Leising et al., all of which are assigned to the assignee of the present invention and incorporated herein by reference. 
     Another preferred metal oxide has the general formula Cu x Ag y V 2 O z , (CSVO). This cathode active material about 0.01≦x≦1.0, about 0.01≦y≦1.0 and about 5.01≦z≦6.5. For a more detailed description of this cathode active material, reference is made to U.S. Pat. No. 5,472,810 to Takeuchi et al. and U.S. Pat. No. 5,516,340 to Takeuchi et al., both of which are assigned to the assignee of the present invention and incorporated herein by reference. 
     Additional cathode active materials for a primary cell include manganese dioxide, cobalt oxide, nickel oxide, copper vanadium oxide, titanium disulfide, copper oxide, copper sulfide, iron sulfide, iron disulfide, fluorinated carbon, and mixtures thereof. 
     In secondary cells, the positive electrode preferably comprises a lithiated material that is stable in air and readily handled. Examples of such air-stable lithiated cathode active materials include oxides, sulfides, selenides, and tellurides of such metals as vanadium, titanium, chromium, copper, molybdenum, niobium, iron, nickel, cobalt and manganese. The more preferred oxides include LiNiO 2 , LiMn 2 O 4 , LiCoO 2 , LiCo 0.92 Sn 0.08 O 2  and LiCo 1−x Ni x O 2 . 
     To discharge such secondary cells, the lithium metal comprising the positive electrode is intercalated into the carbonaceous negative electrode by applying an externally generated electrical potential to recharge the cell. The applied recharging electrical potential serves to draw lithium ions from the cathode active material, through the electrolyte and into the carbonaceous material of the negative electrode to saturate the carbon. The resulting Li x C 6  negative electrode can have an x ranging from about 0.1 to about 1.0. The cell is then provided with an electrical potential and is discharged in a normal manner. 
     An alternate secondary cell construction comprises intercalating the carbonaceous material with the active lithium material before the negative electrode is incorporated into the cell. In this case, the positive electrode body can be solid and comprise, but not be limited to, such active materials as manganese dioxide, silver vanadium oxide, titanium disulfide, copper oxide, copper sulfide, iron sulfide, iron disulfide and fluorinated carbon. However, this approach is compromised by problems associated with handling lithiated carbon outside the cell. Lithiated carbon tends to react when contacted by air or water. 
     The above described cathode active materials, whether of a primary or a secondary chemistry, are formed into an electrode body for incorporation into an electrochemical cell by mixing one or more of them with a conductive additive such as acetylene black, carbon black and/or graphite. Metallic materials such as nickel, aluminum, titanium and stainless steel in powder form are also useful as conductive diluents when mixed with the above listed active materials. The positive electrode of both a primary and a secondary cell further comprises a binder material that is preferably a fluoro-resin powder such as powdered polytetrafluoroethylene (PTFE) or powdered polyvinylidene fluoride (PVDF). More specifically, a preferred cathode active material for a primary cell comprises SVO in any one of its many phases, or mixtures thereof, and/or CSVO mixed with a binder material and a conductive diluent. A preferred cathode active material for a secondary cell comprises lithium cobalt oxide mixed with a binder material and a conductive diluent. 
     In that respect, a preferred positive electrode active admixture according to the present invention comprises from about 80% to 99%, by weight, of a cathode active material comprising either one or both of the SVO and CSVO materials for a primary cell or lithium cobalt oxide for a secondary cell mixed with a suitable binder, a conductive diluent and at least one of the above carbonate compounds. The resulting blended active mixture is formed into a freestanding electrode structure in the above described drop-fill assembly  10 . Electrodes prepared as described above may be in the form of one or more plates operatively associated with at least one or more plates of a counter electrode, or in the form of a strip wound with a corresponding strip of the counter electrode in a structure similar to a “jellyroll”. 
     In order to prevent internal short circuit conditions, the positive electrode is separated from the negative electrode by a suitable separator material. The separator is of electrically insulative material, and the separator material also is chemically unreactive with the negative and positive electrode materials and both chemically unreactive with and insoluble in the electrolyte. In addition, the separator material has a degree of porosity sufficient to allow flow therethrough of the electrolyte during the electrochemical reaction of the cell. Illustrative separator materials include fabrics woven from fluoropolymeric fibers including polyvinylidine fluoride, polyethylenetetrafluoroethylene, and polyethylenechlorotrifluoroethylene used either alone or laminated with a fluoropolymeric microporous film, nonwoven glass, polypropylene, polyethylene, glass fiber materials, ceramics, a polytetrafluoroethylene membrane commercially available under the designation ZITEX (Chemplast Inc.), a polypropylene membrane commercially available under the designation CELGARD (Celanese Plastic Company, Inc.) and a membrane commercially available under the designation DEXIGLAS (C. H. Dexter, Div., Dexter Corp.). The separator may also be composed of non-woven glass, glass fiber materials and ceramic materials. 
     The form of the separator typically is a sheet that is placed between the negative and positive electrodes and in a manner preventing physical contact there between. Such is the case when the negative electrode is folded in a serpentine-like structure with a plurality of positive electrode plates disposed between the folds and received in a cell casing or when the electrode combination is rolled or otherwise formed into a cylindrical “jellyroll” configuration. 
     The primary and secondary electrochemical cells of the present invention further include a nonaqueous, ionically conductive electrolyte. The electrolyte serves as a medium for migration of ions between the negative and the positive electrodes during the electrochemical reactions of the cell, and nonaqueous solvents suitable for the present invention are chosen so as to exhibit those physical properties necessary for ionic transport (low viscosity, low surface tension and wettability). Suitable nonaqueous solvents are comprised of an inorganic salt dissolved in a nonaqueous solvent system. 
     For both a primary and a secondary cell, the electrolyte preferably comprises an alkali metal salt dissolved in a mixture of aprotic organic solvents comprising a low viscosity solvent including organic esters, ethers, dialkyl carbonates, and mixtures thereof, and a high permittivity solvent including cyclic carbonates, cyclic esters, cyclic amides, and mixtures thereof. Low viscosity solvents include tetrahydrofuran (THF), diisopropylether, methyl acetate (MA), diglyme; triglyme, tetraglyme, 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), 1-ethoxy,2-methoxyethane (EME), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and mixtures thereof. High permittivity solvents include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), acetonitrile, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide, γ-valerolactone, γ-butyrolactone (GBL), N-methyl-pyrrolidinone (NMP), and mixtures thereof. 
     The preferred electrolyte for both a primary and a secondary cell comprises a lithium salts selected from the group of LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 , LiClO 4 , LiAlCl 4 , LiGaCl 4 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 CF 3 ) 2 , LiSCN, LiO 3 SCF 2 CF 3 , LiC 6 F 5 SO 3 , LiO 2 CCF 3 , LiSO 3 F, LiNO 3 , LiB(C 6 H 5 ) 4 , LiCF 3 SO 3 , and mixtures thereof. Suitable salt concentrations typically range between about 0.8 to 1.5 molar. 
     In the present invention, the preferred primary electrochemical cell has a negative electrode of lithium metal and a positive electrode of silver vanadium oxide contacted to one side of a current collector and CF x  contacted to the other. For more detail description regarding this type of cathode construction, reference is made to U.S. Pat. No. 6,551,747 to Gan, which is assigned to the assignee of the present invention and incorporated herein by reference. For this primary couple, the preferred activating electrolyte is 1.0M to 1.4M LiAsF 6  dissolved in a 50/50 mixture, by volume, of propylene carbonate and 1,2-dimethoxyethane. A preferred electrolyte for a secondary cell of a carbon/LiCoO 2  couple comprises a solvent mixture of EC:DMC:EMC:DEC. 
     The assembly of the primary and secondary cells described herein is either in the form of a wound element configuration or of a multi-plate design with the negative electrode on the outside to make electrical contact with the cell case in a case-negative configuration. The cell assembly is inserted into a metallic case of a suitable size dimension. The metallic case may comprise materials such as stainless steel, mild steel, nickel-plated mild steel, titanium, tantalum or aluminum, but not limited thereto, so long as the metallic material is compatible for use with components of the cell. 
     A cell header comprising a first hole to accommodate a glass-to-metal seal/terminal pin feedthrough and a second hole for electrolyte filling are provided to close the casing. The glass used is of a corrosion resistant type having up to about 50% by weight silicon such as CABAL 12, TA 23, FUSITE 425 or FUSITE 435. The positive terminal pin feedthrough preferably comprises titanium although molybdenum, aluminum, nickel alloy, or stainless steel can also be used. The cell header is typically of a material similar to that of the case. The positive terminal pin supported in the glass-to-metal seal is, in turn, supported by the header, which is welded to the case containing the electrode stack. The cell is thereafter filled with the electrolyte solution described hereinabove and hermetically sealed such as by close-welding a stainless steel ball over the fill hole, but not limited thereto. 
     The above assembly describes a case-negative cell, which is the preferred construction of either the exemplary primary or secondary cell of the present invention. As is well known to those skilled in the art, the exemplary primary and secondary electrochemical systems of the present invention can also be constructed in case-positive configurations. 
     It is appreciated that various modifications to the present inventive concepts described herein may be apparent to those of ordinary skill in the art without departing from the spirit and scope of the present invention as defined by the herein appended claims.