Patent Publication Number: US-7214446-B1

Title: Batteries with electroactive nanoparticles

Description:
This application is a continuation of commonly assigned U.S. patent application Ser. No. 09/333,099 filed Jun. 15, 1999, now U.S. Pat. No. 6,130,007 to Bi et al., entitle “Batteries With Electroactive Nanoparticles,” incorporated herein by reference, which is a continuation of U.S. patent application Ser. No. 08/897,776 Jul. 21, 1997, now U.S. Pat. No. 5,952,125. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to batteries, especially lithium batteries and lithium ion batteries, incorporating nanoparticles, such as vanadium oxide nanoparticles, as an electroactive material. 
     BACKGROUND OF THE INVENTION 
     The microminiaturization of electronic components has created widespread growth in the use of portable electronic devices such as cellular phones, pagers, video cameras, facsimile machines, portable stereophonic equipment, personal organizers and personal computers. The growing use of portable electronic equipment has created ever increasing demand for improved power sources for these devices. Relevant batteries include primary batteries, i.e., batteries designed for use through a single charging cycle, and secondary batteries, i.e., batteries designed to be rechargeable. Some batteries designed essentially as primary batteries may be rechargeable to some extent. 
     Batteries based on lithium have been the subject of considerable development effort and are being sold commercially. Lithium based batteries generally use electrolytes containing lithium ions. The anodes for these batteries can include lithium metal (lithium batteries), or compositions that intercalate lithium (lithium ion batteries). Preferred electroactive materials for incorporation into the cathodes are compositions that intercalate lithium. The compositions that intercalate lithium, for use in the cathodes, generally are chalcogenides such as metal oxides that can incorporate the lithium ions into their lattice. Vanadium oxides are examples of promising compounds for the production of cathodes because of their high theoretical energy densities. 
     SUMMARY OF THE INVENTION 
     In a first aspect, this invention features a cathode composition including vanadium oxide particles having an average diameter less than about 1000 nm and a binder. The vanadium oxide particles preferably have an average diameter from about 5 nm to about 150 nm and more preferably from about 5 nm to about 50 nm. The binder can be polyvinylidene fluoride, polyethylene oxide, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylates, mixtures thereof or copolymers thereof. The cathode composition can further include supplementary electrically conductive particles. The supplementary electrically conductive particles can include carbon. The cathode composition preferably includes from about 60 percent by weight to about 98 percent by weight vanadium oxide particles. 
     In another aspect, the invention features a battery including an anode, a cathode comprising vanadium oxide particles having an average diameter less than about 1000 nm and a binder, and a separator element disposed between the anode and cathode. The anode can include lithium metal or a composition that intercalates lithium. Suitable intercalation compounds for the anode include, for example, carbon compounds. The vanadium oxide particles preferably have an average diameter from about 150 nm to about 5 nm. The separator element can include a polymer electrolyte or a porous polymeric material. 
     In another aspect, the invention features a battery including an anode, an electrolyte, a cathode and a separator element disposed between the anode and the cathode, the electrolyte comprising lithium ions and the cathode comprising nanoparticles of intercalation type, electroactive material and a binder, wherein the electroactive material in the cathode performs with an energy density greater than about 900 Wh/kg during discharge of the battery. The battery can be a secondary battery. The electroactive material of the cathode can have an energy density from about 950 Wh/kg to about 1200 Wh/kg. The electroactive material can include vanadium oxide. The electroactive material in the anode can include a lithium intercalation composition. 
     Batteries based on nanoparticles such as vanadium oxide nanoparticles lead to lithium batteries and lithium ion batteries with improved performance characteristics. In particular, the vanadium oxide nanoparticles have increased energy densities compared with larger diameter vanadium oxide particles. Using electroactive materials with increased energy densities yields batteries with higher capacities for a given amount of electroactive material. In this way, longer lasting, lighter and/or smaller batteries can be produced. 
     Other features and advantages of the invention follow from the detailed description below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view of an embodiment of a laser pyrolysis apparatus taken through the middle of the laser radiation path. The upper insert is a bottom view of the injection nozzle, and the lower insert is a top view of the collection nozzle. 
         FIG. 2  is a schematic, sectional view of an oven taken through the center of the quartz tube. 
         FIG. 3  is a schematic, perspective view of a battery of the invention. 
         FIG. 4  is a schematic, perspective view of the three electrode arrangement used in the examples. 
         FIG. 5  is an x-ray diffractogram of VO 2  nanoparticles. 
         FIG. 6  is a transmission electron micrograph view of crystalline VO 2  nanoparticles. 
         FIG. 7  depicts the discharge/recharge cycling of a battery of the invention using VO 2  electroactive particles. 
         FIG. 8  is an x-ray diffractogram of 2-D crystalline V 2 O 5 . 
         FIG. 9  is an x-ray diffractogram of amorphous V 2 O 5    
         FIG. 10  is an x-ray diffractogram of mixed phase V 6 O 13 +V 2 . 
         FIG. 11  is an x-ray diffractogram of crystalline V 2 O 5 , sample A. 
         FIG. 12  is an x-ray diffractogram of crystalline V 2 O 5 , sample B. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Vanadium oxide particles have been produced having diameters less than a micron with vanadium in a variety of oxidation states and with a variety of lattice structures. The small size of the particles results in a significantly increased surface area for a given weight of material. Appropriate vanadium oxide nanoparticles incorporated into a cathode for a lithium based battery exhibit a significantly increased energy density relative to comparable materials of larger particle size. 
     The vanadium oxide nanoparticles not only have high surface area resulting from their small size, but they also can have a high degree of crystallinity. This high degree of crystallinity generally is maintained throughout each nanoparticle. Nanocrystalline materials generally do not rely on pores to generate a high surface area. Pores can be undesirable since they represent a discontinuity in the crystalline lattice. The surface area of the nanoparticles generally results only from the faces of the particle. 
     Amorphous nanoparticles can also be produced. Amorphous vanadium oxides can have very high energy densities. Amorphous bulk particles can undergo crystalline rearrangements that reduce the energy density during the cycling of secondary batteries. 
     The vanadium oxide nanoparticles can be incorporated into a cathode film with a polymeric binder. The resulting film is appropriate for use as a cathode. While some of the vanadium oxides are reasonable electrical conductors, the film preferably incorporates additional electrically conductive particles held by the binder along with the vanadium oxide particles. The cathode film can be used in a lithium battery or a lithium ion battery. 
     A. Production of Vanadium Oxide Nanoparticles 
     Laser pyrolysis has been found to be a powerful technique for producing vanadium oxides nanoparticles. In addition, the nanoscale vanadium oxide particles produced by laser pyrolysis can be subjected to additional processing to alter the properties of the nanoparticles without destroying the nanoparticle size. 
     A basic feature of successful application of laser pyrolysis for the production of vanadium oxide nanoparticles is the production of a molecular stream containing a vanadium precursor, a radiation absorber and an oxygen source. The molecular stream is pyrolyzed by an intense laser beam. The intense heat resulting from the absorption of the laser radiation induces the oxidation of the vanadium precursor in the oxidizing environment. As the molecular stream leaves the laser beam, rapid quenching of the vanadium materials results in particle formation. 
     The reaction conditions determine the qualities of the vanadium oxide particles produced by laser pyrolysis. The appropriate reaction conditions to produce a certain type of nanoparticles generally depend on the design of the particular apparatus. The reaction conditions for laser pyrolysis can be controlled relatively precisely in order to produce vanadium oxides with desired properties. 
     Appropriate precursor compounds generally include vanadium compounds with sufficient vapor pressure to yield desired amounts of precursor vapor. Suitable vanadium precursor compounds include, for example, VCl 3 , VCl 4 , VCCl, V(CO) 6  and VOCl 3 . The Cl in these representative precursor compounds can be replaced with other halogens, e.g., Br, I and F. Preferred oxygen sources include, for example, O 2 , CO, CO 2 , O 3  and mixtures thereof. 
     Preferred lasers include, for example, CO 2  lasers, which produce infrared radiation. Infrared absorbers for inclusion in the molecular stream include, for example, C 2 H 4 , NH 3 , SF 6  and O 3 . O 3  can act as both an infrared absorber and as an oxygen source. The radiation absorber, such as the infrared absorber, absorbs energy from the radiation beam and distributes the energy as heat to the other reactants to drive the pyrolysis. 
     An inert shielding gas can be used to reduce the amount of reactant and product molecules contacting the reactant chamber components. For the production of vanadium oxide nanoparticles, appropriate shielding gases include, for example, Ar, He and N 2 . 
     Referring to  FIG. 1 , a pyrolysis apparatus  100  involves a reactant supply system  102 , reaction chamber  104 , collection system  106  and laser  108 . Reactant supply system  102  includes a source  120  of vanadium precursor. For liquid precursors, a carrier gas from carrier gas source  122  can be introduced into precursor source  120 , containing liquid precursor to facilitate delivery of the precursor. The carrier gas from source  122  preferably is either an infrared absorber or an inert gas. The carrier gas preferably is bubbled through the liquid vanadium precursor. The quantity of precursor vapor in the reaction zone is roughly proportional to the flow rate of the carrier gas. 
     Alternatively, carrier gas can be supplied directly from an infrared absorber source  124  or an inert gas source  126 , as appropriate. The oxidizing agent is supplied from source  128 , which can be a gas cylinder. The gases from the vanadium precursor source  120  are mixed with gases from oxidizing agent source  128 , infrared absorber source  124  and inert gas source  126  by combining the gases in a single portion of tubing  130 . The gases are combined a sufficient distance from the reaction chamber  104  such that the gases become well mixed prior to their entrance into the reaction chamber  104 . The combined gas in tube  130  passes through a duct  132  into rectangular channel  134 , which forms part of an injection nozzle for directing reactants into the reaction chamber. 
     Flow from sources  122 ,  124 ,  126  and  128  are preferably independently controlled by mass flow controllers  136 . Mass flow controllers  136  preferably provide a controlled flow rate from each respective source. Suitable mass flow controllers include, for example, Edwards Mass Flow Controller, Model 825 series, from Edwards High Vacuum International, Wilmington, Mass. 
     Inert gas source  138  is also connected to a inert gas duct  140 , which flows into annular channel  142 . A mass flow controller  144  regulates the flow of inert gas into inert gas duct  140 . Inert gas source  126  can also function as inert gas source for duct  140 , if desired. 
     The reaction chamber  104  includes a main chamber  200 . Reactant supply system  102  connects to the main chamber  200  at injection nozzle  202 . The end of injection nozzle  202  has an annular opening  204  for the passage of inert shielding gas and a rectangular slit  206  for the passage of reactant gases to form a molecular stream in the reaction chamber. Annular opening  204  has an diameter of about 1.5 inches and a width along the radial direction of about 1/16 in. The flow of shielding gas through annular opening  204  helps to prevent the spread of the reactant gases and product particles throughout reaction chamber  104 . 
     Tubular sections  208 ,  210  are located on either side of injection nozzle  202 . Tubular sections  208 ,  210  include ZnSe windows  212 ,  214 , respectively. Windows  212 ,  214  are about 1 inch in diameter. Windows  212 ,  214  are preferably plano-focusing lenses with a focal length equal to the distance between the center of the chamber to the surface of the lens to focus the beam to a point just below the center of the nozzle opening. Windows  212 ,  214  preferably have an antireflective coating. Appropriate ZnSe lenses are available from Janos Technology, Townshend, Vt. Tubular sections  208 ,  210  provide for the displacement of windows  212 ,  214  away from main chamber  200  such that windows  212 ,  214  are less likely to be contaminated by reactants or products. Window  212 ,  214  are displaced, for example, about 3 cm from the edge of the main chamber  200 . 
     Windows  212 ,  214  are sealed with a rubber o-ring to tubular sections  208 ,  210  to prevent the flow of ambient air into reaction chamber  104 . Tubular inlets  216 ,  218  provide for the flow of shielding gas into tubular sections  208 ,  210  to reduce the contamination of windows  212 ,  214 . Tubular inlets  216 ,  218  are connected to inert gas source  124  or to a separate inert gas source. In either case, flow to inlets  216 ,  218  preferably is controlled by a mass flow controller  220 . 
     Laser  108  is aligned to generate a laser beam  222  that enters window  212  and exits window  214 . Windows  212 ,  214  define a laser light path through main chamber  200  intersecting the flow of reactants at reaction zone  224 . After exiting window  214 , laser beam  222  strikes power meter  226 , which also acts as a beam dump. An appropriate power meter is available from Coherent Inc., Santa Clara, Calif. Laser  108  can be replaced with an intense conventional light source such as an arc lamp. Preferably, laser  108  is an infrared laser, especially a CW CO 2  laser such as an 1800 watt maximum power output laser available from PRC Corp., Landing, N.J. or a Coherent® model 525 (Coherent Inc., Santa Clara, Calif.) with a maximum power output of 375 watts. 
     Reactants passing through slit  206  in injection nozzle  202  initiate a molecular stream. The molecular stream passes through reaction zone  224 , where reaction involving the vanadium precursor takes place. Heating of the gases in reaction zone  224  is extremely rapid, roughly on the order of 10 5 ° C./sec depending on the specific conditions. The reaction is rapidly quenched upon leaving reaction zone  224 , and nanoparticles  228  are formed in the molecular stream. The nonequilibrium nature of the process allows for the production of nanoparticles with a highly uniform size distribution and structural homogeneity. 
     The path of the molecular stream continues to collection nozzle  230 . Collection nozzle  230  is spaced about 2 cm from injection nozzle  202 . The small spacing between injection nozzle  202  and collection nozzle  230  helps reduce the contamination of reaction chamber  104  with reactants and products. Collection nozzle  230  has a circular opening  232 . Circular opening  232  feeds into collection system  106 . 
     The chamber pressure is monitored with a pressure gauge attached to the main chamber. The preferred chamber pressure for the production of vanadium oxides ranges from about 80 Torr to about 300 Torr. 
     Reaction chamber  104  has two additional tubular sections not shown. One of the additional tubular sections projects into the plane of the sectional view in  FIG. 1 , and the second additional tubular section projects out of the plane of the sectional view in  FIG. 1 . These tubular sections have windows for observing the inside of the chamber. In this configuration of the apparatus, the two additional tubular sections are not used to facilitate production of nanoparticles. 
     Collection system  106  can include a curved channel  250  leading from collection nozzle  230 . Because of the buoyant nature of the nanoparticles, the product nanoparticles follow the flow of the gas around curves. Collection system  106  includes a filter  252  within the gas flow to collect the product nanoparticles. A variety of materials such as teflon, glass fibers and the like can be used for the filter as long as the material is inert and has a fine enough mesh to trap the particles. Preferred materials for the filter include, for example, a glass fiber filter from ACE Glass Inc. Vineland, N.J. 
     Pump  254  is used to maintain collection system  106  at a reduced pressure. A variety of different pumps can be used. Appropriate pumps  254  include, for example, Busch Model B0024 pump from Busch, Inc., Virginia Beach, Va. with a pumping capacity of about 25 cubic feet per minute (cfm). It may be desirable to flow the exhaust of the pump through a scrubber  256  to remove any remaining reactive chemicals before venting into the atmosphere. The entire apparatus  100  can be placed in a fume hood for ventilation purposes and for safety considerations. Generally, the laser remains outside of the fume hood because of its large size. 
     The apparatus is controlled by a computer. Generally, the computer controls the laser and monitors the pressure in the reaction chamber. The computer can be used to control the flow of reactants and/or the shielding gas. The pumping rate is controlled by either a manual needle valve or an automatic throttle valve inserted between pump  254  and filter  252 . As the chamber pressure increases due to the accumulation of particles on filter  252 , the manual valve or the throttle valve can be adjusted to maintain the pumping rate and the corresponding chamber pressure. 
     The reaction can be continued until sufficient nanoparticles are collected on the filter  252  such that the pump can no longer maintain the desired pressure in the reaction chamber  104  against the resistance through filter  252 . When the pressure in the reaction chamber  104  can no longer be maintained at the desired value, the reaction is stopped, and the filter  252  is removed. With this embodiment, about 3–5 grams of nanoparticles can be collected in a single run. Therefore, it is straightforward to produce a macroscopic quantity of nanoparticles, i.e., a quantity visible with the naked eye. 
     The configuration of the reactant supply system  102  and the collection system  106  can be reversed. In this alternative configuration, the reactants can be supplied from the bottom of the reaction chamber while the products are collected from the top of the chamber. In this configuration, it is especially preferred to include a curved section in the collection system so that the collection filter is not mounted directly above the reaction chamber. 
     An alternative design of a laser pyrolysis apparatus has been described. See, commonly assigned U.S. patent application Ser. No. 08/808,850, entitled “Efficient Production of Particles by Chemical Reaction,” incorporated herein by reference. This alternative design is intended to facilitate production of commercial quantities of nanoparticles. 
     As noted above, properties of the vanadium oxide nanoparticles can be modified by further processing. For example, the vanadium oxide nanoparticles can be heated in an oven in an oxidizing environment or an inert environment to alter the oxygen content and/or crystal structure of the vanadium. It has been discovered that the use of mild conditions, i.e., temperatures well below the melting point of the nanoparticles, results in modification of the stoichiometry or crystal structure of vanadium oxides without significantly sintering of the nanoparticles into larger particles. This processing is further discussed in commonly assigned and simultaneously filed, U.S. patent application Ser. No. 08/897,903, entitled “Processing of Vanadium Oxide Particles With Heat,” now U.S. Pat. No. 5,989,514, incorporated herein by reference. The heat processing can be performed on initial particles that were not produced by laser pyrolysis, including particles that do not have a generally spherical shape, i.e., particles that are flat sheets or needle like. 
     An example of an apparatus  400  to perform this processing is displayed in  FIG. 2 . Apparatus  400  includes a tube  402  into which the nanoparticles are placed. Tube  402  is connected to an oxidizing gas source  404  and inert gas source  406 . Oxidizing gas, inert gas or a combination thereof to produce the desired atmosphere are placed within tube  402 . 
     Preferably, the desired gases are flowed through tube  402 . Appropriate active gases to produce an oxidizing environment (oxidizing gas) include, for example, O 2 , O 3 , CO, CO 2  and combinations thereof. The oxidizing gases can be diluted with inert gases such as Ar, He and N 2 . The gases in tube  402  can be exclusively inert gases, if desired. 
     Tube  402  is located within the heating oven or furnace  408 . Oven  408  maintains the relevant portions of tube  402  at a relatively constant temperature, although the temperature can be varied systematically through the processing step, if desired. Temperature in oven  408  generally is measured with a thermocouple  410 . The vanadium oxide particles can be placed in tube  402  within a vial  412 . Vial  412  prevents loss of the particles due to gas flow. Vial  412  generally is oriented with the open end directed toward the direction of the source of gas flow. 
     The precise conditions including the type of oxidizing gas (if any), concentration of oxidizing gas, pressure or flow rate of gas, temperature and processing time can be selected to produce the desired type of product material. The temperatures generally are mild, i.e., significantly below the melting point of the material. The use of mild conditions avoids interparticle sintering resulting in larger particle sizes. Some controlled sintering of the vanadium oxide particles can be performed in oven  408  at somewhat higher temperatures to produce slightly larger average particle diameters. 
     For the processing of vanadium oxides, the temperatures preferably range from about 50° C. to about 1000° C., and more preferably from about 80° C. to about 800° C. The nanoparticles preferably are heated for about 1 hour to about 100 hours. High melting point VO 2  is relatively easy to form in the laser pyrolysis apparatuses described above. VO 2  is a suitable starting product for oxidation to other forms of vanadium oxide. Some empirical adjustment may be required to produce the conditions to generate the desired material. 
     B. Properties of the Vanadium Oxide Nanoparticles 
     Vanadium oxide has a intricate phase diagram due to the many possible oxidation states of vanadium. Vanadium is known to exist in oxidation states between V +5  and V +2 . The energy differences between the oxides with vanadium in the different oxidation states is not large. Therefore, it is possible to produce stoichiometric mixed valence compounds. Known forms of vanadium oxide include VO, VO 1.27 , V 2 O 3 , V 3 O 5 , VO 2 , V 6 O 13 , V 4 O 9 , V 3 O 7 , and V 2 O 5 . Single phase vanadium oxide nanoparticles can be crystalline or amorphous. 
     There are also mixed phase regions of the vanadium oxide phase diagram. In the mixed phase regions, particles can be formed that have domains with different oxidation states or different particles can be simultaneously formed with vanadium in different oxidation states. In other words, certain particles or portions of particles have one stoichiometry while other particles or portions of particles have a different stoichiometry. Non-stoichiometric materials can also be formed. 
     The vanadium oxides generally form crystals with octahedral or distorted octahedral coordination. Specifically, VO, V 2 O 3 , VO 2 , V 6 O 13  and V 3 O 7  can form crystals with octahedral coordination. In addition, V 3 O 7  can form crystals with trigonal bipyramidal coordination. V 2 O 5  forms crystals with square pyramidal or distorted octahedral coordination. V 2 O 5  recently has also been produced in a two dimensional crystal structure. See, M. Hibino, et al., Solid State Ionics 79:239–244 (1995), incorporated herein by reference. When produced under appropriate conditions, the vanadium oxide nanoparticles can be amorphous. The crystalline lattice of the vanadium oxide can be evaluated using x-ray diffraction measurements. 
     Vanadium oxide nanoparticles produced by laser pyrolysis possibly combined with further heat processing preferably have an average diameter of less than a micron, or from about 5 nm to about 500, more preferably from about 5 nm to about 150 nm and even more preferably from about 5 nm to about 50 nm. The nanoparticles generally have a roughly spherical gross appearance. Upon closer examination, the particles generally have facets corresponding to the underlying crystal lattice. Nevertheless, the nanoparticles tend to exhibit growth that is roughly equal in the three physical dimensions to give a gross spherical appearance. Diameter measurements on particles with asymmetries are based on an average of length measurements along the principle axes of the crystal. The measurements along the principle axes preferably are each less than about 1 micron for at least about 95 percent of the nanoparticles, and more preferably for at least about 98 percent of the nanoparticles. 
     Because of their small size, the nanoparticles tend to form loose agglomerates due to van der Waals forces between nearby particles. Nevertheless, the nanometer scale of the particles is clearly observable in transmission electron micrographs of the particles. The particles generally have a surface area corresponding to particles on a nanometer scale as observed in the micrographs. Furthermore, as described below, the nanoparticles manifest unique properties due to their small size and large surface area per weight of material. 
     The nanoparticles preferably have a high degree of uniformity in size. As determined from examination of transmission electron micrographs, the particles generally have a distribution in sizes such that at least about 95 percent of the particles have a diameter greater than about 40 percent of the average diameter and less than about 160 percent of the average diameter. Preferably, the nanoparticles have a distribution of diameters such that at least about 95 percent of the particles have a diameter greater than about 60 percent of the average diameter and less than about 140 percent of the average diameter. In addition, the nanoparticles generally have a high level of purity. The vanadium oxide nanoparticles are expected to have a purity greater than the reactant gases because the crystal formation process tends to exclude contaminants from the lattice. 
     The above described techniques have been successfully applied to the production of nanoparticles of vanadium oxide with several different stoichiometries and with different crystal structures with the same stoichiometry. The structures and compositions have been examined using x-ray defractometry. The sizes of some of the particles have been examined using transmission electron microscopy. The properties of the types of vanadium oxide nanoparticles obtained are summarized in Table 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Stoichiometry 
                 Lattice 
               
               
                   
                   
               
             
            
               
                   
                 Single Phase VO 2   
                 Monoclinic 
               
               
                   
                 Single Phase VO 1.27   
                 Tetragonal 
               
               
                   
                 Single Phase V 2 O 5   
                 Amorphous 
               
               
                   
                   
                 2-D crystals 
               
               
                   
                   
                 Crystalline 
               
               
                   
                 Mixed Phase V 6 O 13  + VO 2   
                 V 6 O 13  majority/Monoclinic 
               
               
                   
                 Mixed Phase V 2 O 3  + VO 2   
                 V 2 O 3  majority/Rhombohedral 
               
               
                   
                   
               
            
           
         
       
     
     Additional information on the production and properties of vanadium oxide nanoparticles is found in commonly assigned and simultaneously filed, U.S. patent application Ser. No. 08/897,778, now U.S. Pat. No. 6,106,798, entitled “Vanadium Oxide Nanoparticles,” incorporated herein by reference. 
     C. Lithium Based Batteries 
     Referring to  FIG. 3 , battery  450  has an anode  452 , a cathode  454  and separator  456  between anode  452  and cathode  454 . A single battery can include multiple cathodes and/or anodes. Electrolyte can be supplied in a variety of ways as described further below. Battery  450  preferably includes current collectors  458 ,  460  associated with anode  452  and cathode  454 , respectively. Multiple current collectors can be associated with each electrode if desired. 
     Lithium has been used in reduction/oxidation reactions in batteries because they are the lightest metal and because they are the most electropositive metal. Certain forms of vanadium oxide are known to incorporate lithium ions into its structure through intercalation or similar mechanisms such as topochemical absorption. Intercalation of lithium ions into suitable forms of a vanadium oxide lattice forms Li x VO y . Appropriate vanadium oxides can be an effective electroactive material for a cathode in either a lithium or lithium ion battery. 
     Lithium intercalated vanadium oxide is formed in the battery during discharge. The lithium leaves the lattice upon recharging, i.e., when a voltage is applied to the cell such that electric current flows into the cathode due to the application of an external EMF to the battery. Intercalation generally is reversible, making certain vanadium oxides suitable for the production of secondary batteries. 
     Cathode  454  includes electroactive nanoparticles such as vanadium oxide nanoparticles held together with a binder. Nanoparticles for use in cathode  454  generally can have any shape, e.g., roughly spherical nanoparticles or elongated nanoparticles. Cathode  454  can include other electroactive nanoparticles such as TiO 2  nanoparticles. The production of TiO 2  nanoparticles has been described, see U.S. Pat. No. 4,705,762, incorporated herein by reference. TiO 2  nanoparticles are expected to exhibit relatively high energy densities in lithium based batteries by analogy with the results discovered for vanadium oxides nanoparticles. 
     The cathode optionally can include electrically conductive particles in addition to the electroactive nanoparticles. These supplementary, electrically conductive particles generally are also held by the binder. Suitable electrically conductive particles include conductive carbon particles such as carbon black, metal particles such as silver particles and the like. 
     With vanadium oxide nanoparticles, very high energy densities have been achieved. Preferred vanadium oxide nanoparticles have energy densities in lithium based batteries significantly greater than the theoretical maximum values for the corresponding bulk vanadium oxide particles. Vanadium oxide nanoparticles preferably have energy densities at least about 150 percent of the theoretical maximum of the bulk material, and more preferably at least about 200 percent of the theoretical maximum of the bulk material. Specifically, preferred vanadium oxide nanoparticles in lithium based batteries have an energy density of at least about 900 Wh/kg, preferably at least about 1000 Wh/kg. Electroactive nanoparticles can have an energy density in the range from 1000 Wh/kg to about 1200 Wh/kg. 
     High loadings of particles can be achieved in the binder. Particles preferably make up greater than about 80 percent by weight of the cathode, and more preferably greater than about 90 percent by weight. The binder can be any of various suitable polymers such as polyvinylidene fluoride, polyethylene oxide, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylates and mixtures and copolymers thereof. 
     Anode  402  can be constructed from a variety of materials that are suitable for use with lithium ion electrolytes. In the case of lithium batteries, the anode can include lithium metal or lithium alloy metal either in the form of a foil, grid or metal particles in a binder. 
     Lithium ion batteries use particles of an composition that can intercalate lithium. The particles are held with a binder in the anode. Suitable intercalation compounds include, for example, graphite, synthetic graphite, coke, mesocarbons, doped carbons, fullerenes, niobium pentoxide and SnO 2 . 
     Current collectors  458 ,  460  facilitate flow of electricity from battery  450 . Current collectors  458 ,  460  are electrically conductive and generally made of metal such as nickel, iron, stainless steel, aluminum and copper and can be metal foil or preferably a metal grid. Current collector  458 ,  460  can be on the surface of their associated electrode or embedded within their associated electrode. 
     The separator element  456  is electrically insulating and provides for passage of at least some types of ions. Ionic transmission through the separator provides for electrical neutrality in the different sections of the cell. The separator generally prevents electroactive compounds in the cathode from contacting electroactive compounds in the anode. 
     A variety of materials can be used for the separator. For example, the separator can be formed from glass fibers that form a porous matrix. Preferred separators are formed from polymers such as those suitable for use as binders. Polymer separators can be porous to provide for ionic conduction. Alternatively, polymer separators can be solid electrolytes formed from polymers such as polyethylene oxide. Solid electrolytes incorporate electrolyte into the polymer matrix to provide for ionic conduction without the need for liquid solvent. 
     Electrolytes for lithium batteries or lithium ion batteries can include any of a variety of lithium salts. Preferred lithium salts have inert anions and are nontoxic. Suitable lithium salts include, for example, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(trifluoromethyl sulfonyl imide), lithium trifluoromethane sulfonate, lithium tris(trifluoromethyl sulfonyl) methide, lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, lithium chloride and lithium perfluorobutane. 
     If a liquid solvent is used to dissolve the electrolyte, the solvent preferably is inert and does not dissolve the electroactive materials. Generally appropriate solvents include, for example, propylene carbonate, dimethyl carbonate, diethyl carbonate, 2-methyl tetrahydrofuran, dioxolane, tetrahydrofuran, 1,2-dimethoxyethane, ethylene carbonate, γ-butyrolactone, dimethyl sulfoxide, acetonitrile, formamide, dimethylformamide and nitromethane. 
     The shape of the battery components can be adjusted to be suitable for the desired final product, for example, a coin battery, a rectangular construction or a cylindrical battery. The battery generally includes a casing with appropriate portions in electrical contact with current collectors and/or electrodes of the battery. If a liquid electrolyte is used, the casing should prevent the leakage of the electrolyte. The casing can help to maintain the battery elements in close proximity to each other to reduce resistance within the battery. A plurality of battery cells can be placed in a single case with the cells connected either in series or in parallel. 
     EXAMPLES 
     Vanadium oxide based lithium batteries were evaluated to determine the charge capacity and energy density of the vanadium oxide powders used as active materials in the cathodes. The batteries tested in the following examples were all produced following a common procedure. The vanadium oxide powders (VO) were mixed with a conductive acetylene black powder (AB) (Catalog number 55, Chevron Corp.) at a ratio of 60:30. The powder mixture was ground with a mortar and palette to thoroughly mix the powders. 
     A few drops of polyvinylidene fluoride (PVDF) solution were added to the homogeneous powder mixture. The 10 percent PVDF solution included PVDF (Catalog reference R-1, Elf Atochem North America, Inc., Philadelphia, Pa.) dissolved in 1-methyl-2-pyrroidinone (Aldrich Chemical Co., Milwaukee, Wis.). The final ratio of VO:AB:PVDF was 60:30:10. The resulting slurry was spread onto a preweighed nickel metal mesh. The mesh with the slurry was baked in a vacuum oven overnight at 120° C. to remove the solvent and residual moisture. After removal from the oven, the electrodes were immediately placed in a glove box (Vacuum Atmosphere Co., Hawthorne, Calif.) under an argon atmosphere and weighted again. 
     All discharge/charge experiments were conducted in the glove box. The water and oxygen concentrations in the glove box were measured to be less than 1 ppm and 1.5 ppm, respectively. The samples were tested in a three electrode configuration, as shown if  FIG. 4 . In the test set up, cathode  502  on nickel mesh  504  is place in container  506 . Container  506  holds liquid electrolyte  508 . Counter electrode  510  and reference electrode  512  are also placed into container  506 . Lithium metal was used as both counter electrode and reference electrode. The electrodes are connected to a battery testing system  514 . 
     No separator is needed for this testing configuration since the electrodes are physically separated. Alternatively, the liquid electrolyte can be viewed as the separator. The liquid electrolyte (from Merck &amp; Co., Inc.) was 1M LiClO 4 , in propylene carbonate. 
     The samples were tested at the same discharge/charge rate of C/20 (i.e., a rate such that the cathode would be fully discharged in 20 hours), and cycled between 4.0 volts and 1.8 volts at 25° C. The measurements were controlled by an Arbin Battery Testing System, Model BT4023, from Arbin Instruments, College Station, Tex. The charging/discharging profiles were recorded, and the discharge capacity and energy density of the active materials were obtained. 
     The energy density is evaluated by the integral over the discharge time of the voltage multiplied by the current divided by the mass of the active material. The current is kept approximately constant during discharge. Currents used during testing ranged from about 0.08 mA to about 0.12 mA. The current is adjusted to have an approximately constant current density for all the tests. The current density was about 0.1 mA/cm 2 . The active material mass ranged from about 5 to about 17 mg. 
     Comparative Example 1 
     Commercial V 6 O 13    
     Commercial V 6 O 13  was purchased from Alfa Aesar, a Johnson Matthey Company, Ward Hill, Mass. A 7.8 mg quantity of the commercial V 6 O 13  powder was processed into a cathode and tested in a lithium battery, as described above. Over the course of the 170 hour test, the battery was discharged three times. The initial voltage was 3.54 V. The cell had a discharge capacity of 246.2 Ah/kg and an energy density of the cathode active material of 610.1 Wh/kg. This energy density compared with a theoretical maximum value of 890 Wh/kg based on the reversible intercalation of up to 8 lithium ions per unit cell of vanadium oxide. 
     Example 1 
     VO 2  Nanoparticles 
     Nanoscale VO 2  particles were produced by laser pyrolysis using the apparatus shown in  FIG. 1 . The conditions for the synthesis are presented in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Typical Reaction Parameter Values 
               
            
           
           
               
               
               
               
               
            
               
                 Phase 
                 VO 2   
                 V 2 O 5   
                 V 2 O 5   
                 V 6 O 13  + VO 2   
               
               
                   
               
               
                 Crystal 
                 Monoclinic 
                 2D crystal 
                 Amorphous 
                 Monoclinic 
               
               
                 Structure 
               
               
                 Pressure (Torr) 
                 320 
                 300 
                 135 
                 110 
               
               
                 Argon - Win 
                 700 
                 700 
                 700 
                 700 
               
               
                 (sccm) 
               
               
                 Argon - Sld. 
                 5.6 
                 1.12 
                 0.98 
                 2.1 
               
               
                 (slm) 
               
               
                 Ethylene 
                 460 
                 268 
                 603 
                 173 
               
               
                 (sccm) 
               
               
                 Carrier Gas 
                 Ethyl. 
                 676 (Ar) 
                 116 (Ar) 
                 140 (Ar) 
               
               
                 (sccm) 
               
               
                 Oxygen (sccm) 
                 36 
                 400 
                 284 
                 88 
               
               
                 Laser Output 
                 96 
                 67 
                 180 
                 192 
               
               
                 (watts) 
               
               
                 Nozzle 
                 ⅝ × 1/16 
                 ⅝ × 1/16 
                 ⅝ × 1/16 
                 ⅝ × ⅛ 
               
               
                 Opening (in) 
               
               
                   
               
               
                 sccm = standard cubic centimeters per minute 
               
               
                 slm = standard liters per minute 
               
               
                 Argon - Win. = argon flow through inlets 216, 218 
               
               
                 Argon - Sld. = argon flow through annular channel 142 
               
            
           
         
       
     
     An x-ray diffractogram of nanoscale VO 2  powders is presented in  FIG. 5 . A transmission electron microscope (TEM) photograph of the particles is shown in  FIG. 6 . An analysis of the TEM photo reveals an average particle size of about 22 nm. A plot of voltage as a function of time during the discharge/charge cycling is shown in  FIG. 7 . A battery produced with these materials yielded a Discharge Capacity of 249 Ah/kg and an energy density of 549 Wh/kg. The Discharge Capacity and Energy Density are nearly twice the values obtained from larger VO 2  particles. These values are higher than the theoretical maximum-stoichiometric energy density of 390 Wh/kg for VO 2  for the bulk material at 25° C. See, K. West et al., “Vanadium Oxides as Electrode Materials for Rechargeable Lithium Cells,” J. of Power Sources 20:165–172 (1987), incorporated herein by reference. 
     Example 2 
     Singe Phase 2 D-VO 2 O 5 , Nanoparticles 
     Single phase 2-D V 2 O 5  nanoparticles were produced by laser pyrolysis using the apparatus shown in  FIG. 1 . The conditions for the synthesis are presented in Table 2. 
     A x-ray diffractogram of nanoscale 2-D V 2 O 5  powders is presented in  FIG. 8 . An analysis of a TEM photo of the materials reveals an average particle size of about 20 nm. A battery produced with these materials yielded a Discharge Capacity of 146 Ah/kg and an Energy Density of 380 Wh/kg. 
     Example 3 
     Amorphous V 2 O 5  Nanoparticles 
     Single phase amorphous V 2 O 5  nanoparticles were produced by laser pyrolysis using the apparatus shown in  FIG. 1 . The conditions for the synthesis are presented in Table 2. 
     A typical x-ray diffractogram of nanoscale amorphous V 2 O 5  nanoparticle powders is presented in  FIG. 9 . An analysis of a TEM photo of the materials reveals an average particle size of about 200 nm for the amorphous V 2 O 5  nanoparticles used to form the cathode. Two batteries produced with these materials yielded Discharge Capacities of 186.1 Ah/kg and 177.3 Ah/kg, and Energy Densities of 476 Wh/kg and 446.2 Wh/kg. 
     Example 4 
     Mixed Phase V 6 O 13 /VO 2  Nano-articles 
     Mixed phase crystalline V 6 O 13 /VO 2  nanoparticles were produced by laser pyrolysis using the apparatus shown in  FIG. 1 . The conditions for the synthesis are presented in Table 2. 
     A x-ray diffractogram of the mixed phase nanoscale crystalline V 6 O 13 /VO 2  nanoparticle powders is presented in  FIG. 10 . An analysis of a TEM photo of the materials reveals an average particle size of about 20 to about 30 nm for the mixed phase V 6 O 3 /VO 2  nanoparticles. A battery produced with these materials yielded a Discharge Capacity of 174 Ah/kg and an Energy Density of 403 Wh/kg. 
     Example 5 
     Crystalline V 2 O 5  Nanoparticles 
     The crystalline V 2 O 5  nanoparticles were produced by further processing nanoparticles produced by laser pyrolysis in an oven with an oxygen atmosphere. Two types of nanoparticles produced by laser pyrolysis (Sample A and Sample B) were used for further processing. The nanoparticles of Sample A were amorphous V 2 O 5  particles. The nanoparticles of samples B were crystalline VO 2  nanoparticles. The conditions used for the production of the two samples is shown in Table 3. A third sample was produced by laser pyrolysis using conditions presented in column 3 of Table 3. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Phase 
                 V 2 O 5   
                 VO 2   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Crystal Structure 
                 Amorphous 
                 Monoclinic 
                   
               
               
                 Pressure (Torr) 
                 142.5 
                 127 
                 230 
               
               
                 Argon - Win (sccm) 
                 700 
                 700 
                 700 
               
               
                 Argon - Sld. (slm) 
                 0.98 
                 0.98 
                 5.6 
               
               
                 Ethylene (sccm) 
                 1072 
                 268 
                 2680 
               
               
                 Carrier Gas (Argon) sccm 
                 676 
                 676 
                 980 
               
               
                 Oxygen (sccm) 
                 642 
                 200 
                 700 
               
               
                 Laser Output (watts) 
                 215 
                 220 
                 180 
               
               
                 Nozzle Size 
                 ⅝″ × 1/16″ 
                 ⅝″ × 1/16″ 
                 ⅝″ × ⅛″ 
               
               
                   
               
            
           
         
       
     
     Quantities of nanoparticles from both Sample A and Sample B were further processed in an oven, as schematically shown in  FIG. 2 . The nanoparticles were processed in the oven for 16 hours at 202° C. with an O 2  flow rate of 105.6 sccm. The resulting nanoparticles from both Sample A and Sample B were crystalline V 2 O 5  with characteristic x-ray diffraction spectra as shown in  FIGS. 11 and 12 , respectively. Note that nanoparticles of both amorphous V 2 O 5  and crystalline VO 2  were converted into similar vanadium oxide nanocrystals. 
     The crystalline V 2 O 5  nanoparticles were formed into batteries. The crystalline V 2 O 5  nanoparticles from Sample A yielded a Discharge Capacity of 399 Ah/kg and a Energy Density of 1005 Wh/kg while the crystalline V 2 O 5  nanoparticles from Sample B yielded a Discharge Capacity of 
     Ah/kg and an Energy Density of 919 Wh/kg. Note that crystalline V 2 O 3  nanoparticles have resulted in an Energy Density greater than 1000 Wh/kg, which is greater than a factor of two larger than estimated theoretical maximum values for bulk V 2 O 5 . 
     The third sample (column 3 of Table 3) was also further processed in an oven. The nanoparticles were heated for 16 hours at 227° C. with an O 2  flow rate of 105.6 sccm. Processing these heat treated particles into a battery as described above, a Discharge Capacity of 438 Ah/kg and an Energy Density of 1121 Wh/kg were measured. 
     Example 6 
     Summary of Oven Treated Nanoparticles And Nanoparticles Produced Directly by Laser Pyrolysis 
     This example summarizes a set of measurements taken with different batches of vanadium oxide nanoparticles. The nanoparticles were either made directly with laser pyrolysis (Table 4A) or with additional heating in an oven under oxidizing conditions (Table 4B). 
     
       
         
           
               
             
               
                 TABLE 4A 
               
             
            
               
                   
               
               
                 Vanadium Oxide Properties 
               
            
           
           
               
               
               
            
               
                   
                 Discharge Capacity 
                 Energy Density 
               
               
                 Material 
                 (Ah/kg) 
                 (Wh/kg) 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Amorphous V 2 O 5   
                 182 
                 461 
               
               
                 VO 2 * 
                 137 
                 328 
               
               
                 2D − V 2 O 5 ** 
                 146 
                 380 
               
               
                 VO 2   
                 235 
                 519 
               
               
                 VO 2   
                 249 
                 549 
               
               
                 VO 2   
                 168 
                 377 
               
               
                 VO 1.27   
                 118 
                 270 
               
               
                 V 2 O 3   
                 94 
                 209 
               
               
                 Mixed Phase VO 2 /V 6 O 13   
                 228 
                 510 
               
               
                 Amorphous V 2 O 5   
                 188 
                 445 
               
               
                 Mixed Phase - V 6 O 13 /VO 2   
                 174 
                 403 
               
               
                   
               
               
                 *Two measurements were made with the same nanoparticles. The individual values were 140 Ah/kg and 133 Ah/kg (Discharge Capacity), and 323 Wh/kg and 333 Wh/kg (Energy Density) 
               
               
                 **Two measurements were made with the same nanoparticles. The individual values were 146 Ah/kg and 146 Ah/kg (Discharge Capacity), and 378 Wh/kg and 381 Wh/kg (Energy Density). 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4B 
               
             
            
               
                   
               
               
                 Vanadium Oxide Properties - Heat Treated 
               
            
           
           
               
               
               
            
               
                   
                 Discharge Capacity 
                 Energy Density 
               
               
                 Material 
                 (Ah/kg) 
                 (Wh/kg) 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Orthorhombic V 2 O 5   
                 336 
                 848 
               
               
                 Mixed Phase VO 2 /V 2 O 5   
                 297 
                 721 
               
               
                 Orthorhombic V 2 O 5   
                 399 
                 1005 
               
               
                 Orthorhombic V 2 O 5   
                 370 
                 919 
               
               
                 2-D V 2 O 5   
                 292 
                 738 
               
               
                 Mixed Phase 2D V 2 O 5 /VO 2   
                 304 
                 751 
               
               
                   
                 438 
                 1121 
               
               
                   
               
            
           
         
       
     
     The embodiments described above are intended to be representative and not limiting. Additional embodiments of the invention are within the claims. As will be understood by those skilled in the art, many changes in the methods and apparatus described above may be made by the skilled practitioner without departing from the spirit and scope of the invention, which should be limited only as set forward in the claims which follow.