MATERIALS BY SPRAYING

FIELD

[0001] Embodiments of the present invention relate generally to lithium-ion batteries, and more specifically, to a method of fabricating such batteries using thin-film deposition processes.

BACKGROUND

[0002] Fast-charging, high-capacity energy storage devices, such as supercapacitors and lithium (Li) ion batteries, are used in a growing number of applications, including portable electronics, medical devices, transportation, grid- connected large energy storage, renewable energy storage, and uninterruptible power supplies (UPS). In modern rechargeable energy storage devices, the current collector is made of an electric conductor. Examples of materials for the positive current collector (the cathode) include aluminum, stainless steel, and nickel. Examples of materials for the negative current collector (the anode) include copper (Cu), stainless steel, and nickel (Ni). Such collectors can be in the form of a foil, a film, or a thin plate, having a thickness that generally ranges from about 6 to 50 pm.

[0003] A typical lithium ion battery consists of a carbon anode and a lithium metal oxide or phosphate cathode separated by an electrolyte liquid consisting of a lithium salt such as LiPF ₆ , LiBF ₄ , or LiCIO ₄ in an organic solvent such as ethylene carbonate, or by a solid polymer electrolyte, such as polyethylene oxide, complexed with lithium salts and/or filled with liquid electrolytes. The cathode material is typically selected from lithium transition metal oxides, such as LiMn ₂ O , LiCoO _2i LiNiO ₂ , or combinations of Ni, Li, Mn, and Co oxides and includes electroconductive particles, such as carbon or graphite, and binder material. The cathode material is considered to be a lithium-intercalation compound, in which the quantity of conductive material is in the range from about 0.1 % to about 15% by weight. The cathode material may be applied to a conductive sheet electrode as a paste and compacted between hot rollers, or sprayed on as a solution or slurry, and the resulting substrate dried to remove the liquid carrier.

[0004] Graphite is frequently used as the anode material and can be in the form of a lithium-intercalation meso-carbon micro bead (MCMB) powder made up of MCMBs having a diameter of approximately 10 pm. The lithium-intercalation MCMB powder is dispersed in a polymeric binder matrix. The polymers for the binder matrix are made of thermoplastic polymers including polymers with rubber elasticity. The polymeric binder serves to bind together the MCMB material powders to preclude crack formation and prevent disintegration of the MCMB powder on the surface of the current collector. The quantity of polymeric binder is in the range of about 0.5% to about 5% by weight. The polymer/MCMB mixture may be applied as a paste and compacted between hot rollers, or in a liquid solution, and the resulting substrate dried to remove the solvent.

[0005] Some Li-ion batteries use separators made from microporous polyolefin polymer, such as polyethylene foam, which are applied in a separate manufacturing step. The separator is generally filled with a liquid electrolyte, as described above, to form the finished battery.

[0006] As the use of thin-film Li-ion batteries continues to grow, there is an ongoing need for thin-film Li-ion batteries that are smaller, lighter, and can be more cost effectively manufactured.

SUMMARY

[0007] Embodiments described herein provide an apparatus for forming an electrochemical layer on a substrate. The apparatus has a first processing stage with a liquid precursor source, an atomizing gas source, and a source of drying energy coupled to a first dispenser. A collection stage proximate the first dispenser has a solids receptacle. A second processing stage has a second dispenser proximate the collection stage and a source of activation energy coupled to the second dispenser. [0008] Some embodiments described herein provide apparatus for depositing an electrochemical layer on a substrate, the apparatus having a drying station, a collection station, and a synthesis station. The drying station has a thermal spray nozzle with a liquid precursor source and an atomizing gas source coupled to a mixing location thereof, an atomizing aperture separating the mixing location from a drying location, a source of chemical or thermal drying energy coupled to the drying location, and an output orifice proximate to the drying location. The collection station has a cyclone separator and a hopper, and a tangential feed point of the cyclone separator is proximate to the output orifice of the drying station. A solids output portion of the cyclone separator is proximate to the hopper, and a source of electrical energy may be coupled to a wall of the cyclone separator. The synthesis station has a plasma spray nozzle with an inlet coupled to an outlet of the hopper and to a plasma forming gas source, and a source of electric power is coupled to the plasma spray nozzle. A flame spray nozzle may be used instead of the plasma spray nozzle in some embodiments. An additive nozzle is located a defined distance from an outlet of the plasma spray nozzle.

[0009] Other embodiments include a method of forming an electrochemical layer on a substrate by forming a precursor powder from a liquid precursor using a continuous drying process, forming an electrochemical precursor from the precursor powder by reacting the precursor powder with oxygen in a plasma or combustion process, dispensing the electrochemical precursor toward a substrate in a stream, adding a polymer binder to the stream to form a deposition mixture, and depositing the deposition mixture on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] So that the manner in which the above-recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. [0011] Figure 1 is a schematic diagram of a Li-ion battery according to one embodiment.

[0012] Figure 2 is a flow diagram summarizing a method according to one embodiment.

[0013] Figure 3 is a schematic cross-sectional view of a film formation apparatus according to one embodiment.

[0014] Figure 4 is a schematic cross-sectional view of a film formation apparatus according to another embodiment.

[0015] Figure 5A is a schematic plan view of a film formation apparatus according to another embodiment.

[0016] Figure 5B is a schematic cross-sectional view of a solids collection apparatus for use in the apparatus of Figure 5A.

[0017] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.

DETAILED DESCRIPTION

[0018] Embodiments disclosed herein generally provide methods and apparatus for forming a film on a substrate. In one embodiment, the film may be an electrochemical film for a thin-film battery, such as a Li-ion battery, or supercapacitor device. An electrochemical precursor or mixture of electrochemical precursors is provided to a processing chamber, where energy is applied to bring the precursor or precursor mixture to a high-temperature state. The high temperature converts the electrochemical precursors into electrochemically active nanocrystals, which form a layer or film on the substrate surface. [0019] Figure 1 is a schematic diagram of a Li-ion battery 100 electrically connected to a load 101 , according to an embodiment of the invention. The primary functional components of Li-ion battery 100 include an anode structure 102, a cathode structure 103, a separator layer 104, and an electrolyte (not shown) disposed within the region between the opposing current collectors 111 and 1 3. A variety of materials may be used as the electrolyte, such as a lithium salt in an organic solvent or a polymeric matrix, which may also be permeated by an organic solvent. The electrolyte is present in anode structure 102, cathode structure 103, and a separator layer 104 in the region formed between the current collectors 111 and 13.

[0020] Anode structure 102 and cathode structure 103 each serve as a half- cell of Li-ion battery 100, and together form a complete working cell of Li-ion battery 100. Anode structure 102 includes a current collector 111 and a first electrolyte containing material 110, such as a carbon-based intercalation host material for retaining lithium ions. Similarly, cathode structure 103 includes a current collector 113 and a second electrolyte containing material 12, such as a metal oxide, for retaining lithium ions. The current collectors 111 and 113 are made of electrically conductive material such as metals. In some cases, a separator layer 104, which may be a dielectric, porous, fluid-permeable layer, may be used to prevent direct electrical contact between the components in the anode structure 102 and the cathode structure 103.

[0021] The electrochemically active material on the cathode side, or positive electrode, of the Li-ion battery 100, may comprise a lithium-containing metal oxide, such as lithium cobalt dioxide (LiCoO ₂ ) or lithium manganese dioxide (LiMnO ₂ ). The electrolyte containing material may be made from an oxide like lithium cobalt oxide, an olivine like lithium iron phosphate, or a spinel like lithium manganese oxide (LiMn ₂ O4), formed in a layer on the positive electrode. In non- lithium embodiments, an exemplary cathode may be made from TiS ₂ (titanium disulfide). Exemplary lithium-containing oxides may be one or more layers of lithium cobalt oxide, or mixed metal oxide, such as LiNi _x Coi _-x- yMn _y O ₂ , for example LiMn ₂ 0 ₄ , which may have up to about 10% excess lithium above stoichiometric proportions. Exemplary phosphates may be iron olivine (LiFePO ₄ ) and it is variants (such as [Li _x Fe _1-x ] _y MgPO4), LiMoPO ₄ , LiCoPO ₄ , Li ₃ V2(PO ₄ )3, LiVOPO _4> LiMP ₂ 0 ₇ , or LiFe ₅ P2O ₇ . Exemplary fluorophosphates may be UVPO4F, UAIPO4F, Li ₅ V(PO4)2F _2j Li ₅ Cr(PO ₄ )2F _2j Li ₂ CoP0 ₄ F, or Li ₂ NiPO ₄ F. Exemplary silicates may be Li ₂ FeSiO ₄ , Li ₂ MnSiO ₄ , or Li ₂ VOSiO ₄ . An exemplary non-lithium compound is Na ₅ V2(PO ₄ )2F3.

[0022] The electrochemically active material on the anode side of the Li-ion battery 100, or negative electrode, may be made from materials described above, namely graphitic microbeads dispersed in a polymer matrix. Additionally, microbeads of silicon, tin, or lithium titanate (Li ₄ Ti ₅ 0 ₁₂ ) may be used with, or instead of, graphitic microbeads to provide the conductive core anode material.

[0023] A cathode material as described above may be formed from liquid precursors in a process and apparatus that decouples a drying operation and a synthesis operation. Figure 2 is a flow diagram summarizing a method 200 according to one embodiment. The method 200 is useful for forming a layer of an electrochemical agent, such as the electrochemically active materials, cathode and/or anode materials described above, on a substrate. The substrate may have a surface that comprises a conductive current collector for a battery structure, as described above with respect to Figure 1. For example, the substrate may have an aluminum electrode surface.

[0024] At 202, a first precursor is provided to a first processing apparatus through a conduit. In one embodiment, the first processing apparatus may be a spraying apparatus or dispenser. The first precursor may comprise one or more electrochemical precursors in a solution. The solution may be an aqueous solution of metal salts or other metal solutes, which may contain miscible carbon- containing liquids such as alcohols. Carbon-containing solutes such as sugars may also be dissolved in the solution. As will be described further below, carbon- containing liquids and solids may usefully add carbon to the electrochemically active material deposited on the substrate. The solution may be atomized by co- flowing with a gas such as argon, helium, nitrogen, air, oxygen, hydrocarbon, or a mixture thereof, through a small opening of the first processing apparatus. For reasonable atomization, the solution will generally have low viscosity, such as about 10 cP or less.

[0025] The first precursor may be an aqueous solution of metal nitrate salts Mx(NO ₃ )y, where x and y depend on the natural valence of the metal M. The metal M may be lithium, manganese, nickel, cobalt, titanium, vanadium, iron, sodium, or chromium, and the first precursor may comprise a plurality of metals. Other salts, such as organic salts, of the above metals may be used instead of, or in addition to, the nitrates. In one embodiment, one or more carboxylates, for example formates, acetates, or tartrates may be used.

[0026] A precursor comprising a plurality of metal salts may be made by mixing standard solutions of individual metal salts in desired quantities. For example, 1 M LiNO ₃ may be added to 1 M Ni(NO ₃ ) ₂ , 1 M Mn(NO ₃ ) ₂ , and/or 1 M Co(NO ₃ ) ₂ or standard solutions of other metals. In some embodiments, excess lithium, such as between about 1 % excess and about 15% excess, for example about 10% excess, may be used to improve performance of a deposited electrochemical layer. For example, 330 ml_ of the 1 M LiNO ₃ may be mixed with 100 ml_ each 1 M solutions of Ni(NO ₃ ) ₂ , Mn(NO ₃ ) ₂ , and Co(NO ₃ ) ₂ to form an aqueous base stock.

[0027] Carbon may be added by mixing in an organic compound, which may be a solvent comprising oxygen and hydrogen, or a sugar, all of which dissolve in, or are miscible with, water. Isopropyl alcohol, ethylene glycol, propylene glycol, are examples of organic solvents that may be used. Sucrose is an exemplary sugar. Oxalyldi hydrazine (a.k.a. oxalic acid hydrazide), and urea are other solutes that may be used. The precursor mixture may be between about 80% and about 100% by weight of the aqueous base stock, between about 0% and about 7% organic solvent, and between about 0% and about 5% sugar by weight. An exemplary electrochemical precursor contains 85% aqueous base stock, 10% isopropyl alcohol, and 5% sugar.

[0028] At 204, energy is applied to the first precursor in the first processing apparatus to form a powdered electrochemical precursor, which may comprise nanocrystals of the electrochemical precursors dissolved in the first precursor. The first processing apparatus may be a flame sprayer, hot air sprayer, or plasma sprayer. Using a flame sprayer, the first precursor is flowed into a nozzle with a flammable gas, such as methane or acetylene, along with an oxygen source such as air or oxygen gas. The flammable gas ignites, releasing energy into the first precursor, which is typically atomized, evaporating the liquids from the first precursor and crystallizing the dissolved solutes. The solution may be atomized using an inert gas such as nitrogen, argon, or helium, or using one of the reacting gases, such as the flammable gas, the oxygen source, or the combined flammable mixture of flammable gas and oxygen source.

[0029] The first processing apparatus typically dries the electrochemical precursors by evaporating or reacting the liquid carriers in the first precursor, crystallizing the electrochemical precursors into a powder. Oxidation reactions performed in the first processing apparatus are performed to add a desired amount of energy to the drying or crystallization process without oxidizing the electrochemical precursors. In most cases, less than about 1 % of the electrochemical precursor will react with oxygen in the first processing apparatus.

[0030] Carbon-containing species in the first precursor may provide different results. Carbon-containing liquids included in the first precursor may also oxidize, in addition to any reactive gases, to add energy to the drying operation. Amorphous carbon particles may form, and may be mixed with the powdered crystals emerging from the flame sprayer. Additionally, carbon-containing solutes in the first precursor may crystallize or form amorphous particles, or a mixture of both, along with the electrochemical precursors in the powder. Adding carbon to the crystals may offer advantages during processing and in performance of the finally deposited film, as discussed further below.

[0031] Alternately, hot air may be mixed with the first precursor in a sprayer to accomplish drying. The hot air may be used to atomize the first precursor, or the first precursor may be atomized using an inert gas, as described above, and then mixed with the hot air. Any carbon-containing liquids in the first precursor may oxidize upon exposure to the hot air, leaving carbon in the powder.

[0032] A plasma sprayer may also be used for converting the first precursor to a powder. The first precursor is atomized into an activation chamber of a plasma sprayer, where electrical energy, such as DC or RF, is coupled into the atomized precursor. The electrical energy may increase the temperature of the first precursor to crystallize the electrochemical solutes, or a reactive material such as a hydrocarbon gas may be added to the mixture to release energy and raise the temperature of the mixture further. Carbon-containing species in the first precursor likewise result in carbon inclusion in the powder from the plasma spray process.

[0033] In general, the energy source, flame, plasma, or hot air, to the sprayer is established prior to providing the first precursor. In the flame spray embodiment, the flammable gas is ignited with the oxygen source, and then atomization of the first precursor into the established flame follows. In the hot air embodiment, flow of the hot air is established before flow of the atomized precursor is started. In the plasma spray embodiment, a plasma is formed using an inert gas flow into the plasma sprayer, and then flow of the precursor mixture is started. Flow of the first precursor to the first processing apparatus is increased until the energy input to the first precursor reaches a lower limit needed to accomplish the desired processing, such as drying. In a continuous drying process, degree of drying may be controlled by adjusting the flow of the first precursor to the first processing apparatus. Energy input may be controlled by adjusting flow of the flammable gas and oxygen source or the ratio thereof, or by adjusting the flow or temperature of the hot air.

[0034] Moisture is generally removed from the powder by the energetic process. The first precursor is heated to a temperature of 200 ^° C or higher, to volatilize the liquid and crystallize the solutes. Pressure drop through the first processing apparatus may be increased by valves or apertures within the first processing apparatus to encourage evaporation. The powder may be completely dried by the energetic spray process, or some moisture may be left to volatilize after spraying, if desired. Particle size may be controlled by processing temperature and atomization flow. In general, finer atomization and higher temperature produce smaller crystals. In the first processing step, it is generally preferred to avoid oxidizing the metal solutes to a great extent. Temperature of the first processing step is therefore typically below about 800°C. At higher severity processing, nanocrystals may be formed. After spraying, the powder is typically maintained at a temperature of 200°C or higher to finish drying and prevent accumulation of moisture and agglomeration subsequent to drying.

[0035] At 206, the particles formed by applying energy to the first precursor are collected using a collection apparatus. Collection of the powder enables the powder to be stored, transported, or fed to a synthesis apparatus for deposition onto a substrate. Further drying may also be done in the collection apparatus. The collection apparatus may also be sealed to prevent moisture intrusion after collecting. The collection apparatus may be a cyclone separator, or other centrifugal separator, or a hopper, any of which may be electrostatically enhanced. The powder is dispensed from the first processing apparatus into a feed point of the collection apparatus. For a cyclone separator, the first processing apparatus may be configured to dispense the powder into a tangential feed point of the cyclone separator. For a hopper, the powder may be dispensed into a central portion of the hopper. Alternately, a centrifugal separator, such as a cyclone separator, may be configured to dispense collected powder into a hopper.

[0036] At 208, the collected powder is fed to a second processing apparatus to synthesize electrochemically active materials and to deposit them onto a substrate. The powder may be mixed with a fluidizing gas to facilitate feeding into the second processing apparatus. An oxygen containing gas is blended with the powder, and energy is added to the mixture to start a reaction of the oxygen with the powder. The energy input may be accomplished through combustion of a flammable gas mixture, or through plasma. In a plasma embodiment, the fluidizing gas may be a plasma forming gas such as argon or nitrogen. Carbon may be added to the reaction mixture in the second processing apparatus, as well, through carbon-containing gases, such a hydrocarbon gases, or liquids, such as organic fluids that may carry carbon-containing solutes. The carbon-containing gas or liquid may be blended in a co-feed with the powder, or may be provided through a separate pathway. In one embodiment, a carbon-containing gas may be used optionally with an inert gas to fluidize the powder for feeding to the second processing apparatus.

[0037] Carbon may be advantageous for inclusion in a deposited cathode material as a binder for the deposited layer, and the conductivity of carbon improves film performance. Adding carbon may also prevent vaporization of the electrochemical material particles during a synthesis operation at high temperatures by forming a low molecular weight amorphous carbon coating over the particles. The coating controls energy input into the particles so that a synthesis reaction proceeds without vaporizing the electrochemical material.

[0038] The second processing apparatus dispenses a stream of crystals or nanocrystals of an electrochemically active material having the general formula LiNi _w Mn _x COyO _z , wherein w, x, and y are each between about .3 and 1.5 and z is between about 1.5 and 2.5. Where the second processing apparatus is a plasma sprayer, plasma is ejected from the apparatus with the crystals entrained in a stream of hot gas and plasma. The crystals may exit the processing chamber at a velocity of between about 1 m/sec and about 600 m/sec, such as about 100 m/sec. the stream forming a plasma jet having a length between about 0.1 and 1.5 m, such as about 1 m. The substrate is typically positioned between about 0.1 and 1.5 m from the plasma chamber.

[0039] In each processing stage, a carbon containing gas, which may be a hydrocarbon such as methane, ethane, acetylene, propane, or another fuel, may be added to the first or the second processing apparatus, for example by mixing with the atomizing gas, or separately provided to the apparatus to add carbon to the mixture, if desired, and to control the energy release of the processing stage. The carbon containing gas may add additional carbon above that in the precursor mixture, or all carbon may be added through the carbon containing gas. Oxygen may be mixed with the carbon containing gas to provide a more energetic reaction in any of the flame spray, plasma spray, or hot air spray embodiments. Total carbon content of the deposited film may be controlled by adjusting a flow rate of the carbon containing gas, the carbon components of the electrochemical precursor, or both. Reaction temperature may also be controlled by adjusting the flow rate of the carbon containing gas and/or oxygen provided therewith. A hydrogen containing carrier gas may also be used to control temperature of the process. Depending on the embodiment, processing temperature is typically maintained between about 200°C and about 2,000°C. For a flame spray embodiment, temperature is typically maintained between about 200°C and about 1 ,000°C, such as between about 400°C and about 800°C. For a plasma spray embodiment, temperature is typically maintained between about 600°C and about 2,000°C, such as between about 800°C and about 1 ,600°C, for example about 900°C.

[0040] An additive may be blended with the crystals outside the processing apparatus as the stream moves toward the substrate. The additive is generally provided to facilitate binding the electrochemical crystals to the substrate. The additive may comprise a binding agent, such as a polymer, to hold the crystals on the surface of the substrate. The binding agent may have some electrical conductivity to improve the performance of the deposited layer. In one embodiment, the binding agent is a carbon containing polymer having a low molecular weight provided at a ratio of less than about 100 polymer molecules per nanocrystal. The low molecular weight polymer may have a weight average molecular weight of less than about 3,000,000 g/mol to promote adhesion of the nanoparticles to the substrate. The ratio of polymer molecules to crystals provides space between the crystals and promotes adhesion without hindering a substantially free flow of electrons and ions through the deposited layer.

[0041] The additive is typically provided as a liquid, for example a solution, suspension, or emulsion. In one embodiment, the additive is a modified styrene- butadiene rubber ("SBR") material in a water emulsion sprayed into the crystal stream exiting the processing chamber. Flow rate of the binder precursor is generally between about 10% and about 75%, for example about 20%, of the mass flow rate of crystals exiting the second processing apparatus.

[0042] If the additive is mixed in with the stream of crystals, the mixing location is selected for its energy content. The residual heat in the crystal stream vaporizes the solvent or continuous phase of the liquid, freeing the additive to contact the crystals. In most such cases, the additive is provided at a distance from an exit point of the second processing apparatus that is between about 60% and about 90% of the distance from the second processing apparatus to the substrate, for example between about 70% and about 80%.

[0043] At 210 the nanocrystals and the additive are formed in the deposited layer on the substrate. A minimal quantity of additive occupies interstices between the crystals to adhere them to the film while allowing free flow of electrons and ions through the deposited layer. In some embodiments, the substrate may be heated during formation of the film to encourage close settling of the crystals before the binding agent, and any residual carbon deposited with the crystals, hardens. Close settling of the crystals is promoted by subsequent collision of crystals emerging from the second processing apparatus so long as the binding medium has not become too resistant to movement.

[0044] The composition of the electrochemical precursor may be changed to change the composition of the deposited electrochemically active layer. To make a spinel material such as LiMn ₂ O , for example, the electrochemical precursor may be made using 100 ml_ of 1 M LiNO ₃ solution and 200 mL of 1 M Mn(N0 ₃ ) ₂ solution, with appropriate amounts of oxygen containing materials. A high capacity layer may be formed by depositing a lithium based material rich in nickel, for example about 60% nickel by weight, or more. Conversely, a high stability layer may be formed by depositing a lithium based material relatively low in nickel, for example less than about 40% nickel by weight. Materials rich in nickel are less stable because the nickel tends to react with many electrolytes used in battery formulations. As described above, this tendency may be controlled by forming a high stability shell around a high capacity core. [0045] In alternate embodiments, particles may be coated with materials other than carbon for synthesis processing. Thin coatings of alumina, aluminum fluoride, aluminum phosphate, aluminum hydroxide, may be used. Aluminum may be added to the process as aluminum alkyls, for example trimethylaluminum. Fluorine may be added as HF. Phosphorus may be added as phosphine, PH ₃ . The coating material are generally applied at a stage of the synthesis process after oxidation of the electrochemical metals.

[0046] In some embodiments, a shell may be formed between each crystal and its coating prior to depositing the crystals on the substrate. The shell may be formed by providing an electrochemical precursor with composition different from the first precursor described above to the second processing apparatus. The material provided to form the shell is generally an electrochemical material desirous of crystallization, so the shell material is generally provided at a location that is adjacent to, or overlaps with, the reactive zone that reacts the crystals from the first processing stage with oxygen. For example, the shell material may be mixed with the powder charged to the second processing apparatus such that the shell material is exposed to the energy of the second processing stage, crystallizing the shell material around the newly formed electrochemical crystals prior to deposition on the substrate.

[0047] In one example, a shell material may be provided to cover a high capacity, low stability, electrochemical core with a high stability shell to prevent reactions between the core and the electrolyte. A high capacity core may be an electrochemical mixture having elevated nickel content, whereas a high stability shell may have lower nickel content. The high nickel content of the core may undergo chemical reactions with some electrolyte materials. Forming a shell of lower nickel content around the high capacity core preserves the capacity of the core while preventing such chemical reactions.

[0048] Porosity of the deposited film may be controlled by adjusting the speed with which the stream of crystals exits the dispenser apparatus. Increasing the speed generally lowers the porosity of the film. Size of the crystals may be controlled by degree of atomization or severity of drying. Finer atomization, for example by increasing pressure of the atomizing gas, results in smaller particles.

[0049] Figure 3 is a schematic cross-sectional view of an apparatus 300 according to one embodiment. The apparatus 300 comprises a processing chamber 302, substrate support 304, and a dispenser 306, which in some embodiments may be a distributor that dispenses material according to certain desired patterns.

[0050] The dispenser 306 comprises an activation chamber 308 and a nozzle 320, though which the activated precursor mixture exits the dispenser 306. A first precursor mixture is provided to the activation chamber 308 through a first source conduit 336 in fluid communication with a precursor source (not shown), which may feature an atomizer for liquid, slurry, or suspension precursors. The first source conduit 336 delivers the first precursor mixture to a flow controller 334, which controls flow of the first precursor through a first precursor delivery conduit 312 into the activation chamber 308. The nozzle 320 carries the activated first precursor mixture from the activation chamber 308 through opening 318 to a mixing zone 322 near the end of the nozzle 320.

[0051] The first precursor in the activation chamber 308 is exposed to an electric field coupled into an interior portion 310 of the activation chamber 308 by a source of electric energy 352. Although shown in the embodiment of Figure 3 as a DC source, the electric source 352 may be an RF or DC source. Electrical insulators 330 may be disposed in the walls of the dispenser 306 to confine the electric energy to the activation chamber 308.

[0052] The mixing zone 322 may be an enclosure adjacent to the activation chamber 308 or a confined space configured to direct the gas mixture toward the substrate in a desired pattern as the mixture reacts. In one example, a second precursor, which may comprise carbon, oxygen, or both, is provided through an annular pathway 328 around the nozzle 320. The annular pathway 328 is configured to flow the second precursor into the activated first precursor in a uniform manner as it exits the nozzle 320. As the precursor streams mix, active species in the first precursor may react with components of the second precursor, generating heat to facilitate the nanocrystallization process, and pressure to propel the activated material outward in a stream of nanocrystals having a spread pattern. The precise geometry of the nozzle 320 and the mixing zone 322 may be adjusted to achieve any desired flow pattern or mixing method. The exact method of mixing devised may help control heat transfer into the nanocrystals. For example, a mixing method incorporating vortex flow of the first and second precursors may be useful in controlling application of heat from the mixing zone reactions, which may include combustion reactions, to the nanocrystals.

[0053] The second precursor is delivered to the mixing zone 322 by a second precursor source conduit 338 in fluid communication with a second precursor source (not shown). The second precursor flows through the flow controller 334 into a second precursor delivery conduit 314 to the annular pathway 328.

[0054] A third precursor may be delivered through a third precursor delivery conduit 316 flowing from a third precursor source conduit 340, in fluid communication with a third precursor source (not shown), through the flow controller 334. The third conduit 324 may have a distribution head configured to distribute the third precursor in a pattern that substantially overlaps the pattern of impact on the substrate by the crystal stream, such that the crystals are secured to the substrate by the third precursor. The third precursor may be the binding agent referred to above. It should be noted that a binding agent is typically not added to the powder exiting the first processing apparatus described above in connection with Figure 2, so in the event the apparatus of Figure 3 is used as the first processing apparatus of the method 200, a third precursor will not be provided.

[0055] In the apparatus of Figure 3, the dispenser 306 may move with respect to the substrate support 304 to form a film over all, or a substantial portion of, a substrate disposed on the substrate support 304. This may be accomplished by moving the dispenser 306, the substrate support 304, or both. For example, the dispenser 306 may be configured to extend and retract across the chamber 302 using an actuator. Alternately, or in addition, the substrate support 304 may have a positioning mechanism, such as a precision x-y stage, schematically represented at 344.

[0056] Exhaust gases leave the chamber 302 through an exhaust portal 330, which may have any convenient configuration. The portal 330 may be a single opening in a wall of the chamber 302, as shown in Figure 3, or multiple such openings, or a circumferential exhaust channel disposed around a circumference of the chamber 302. The exhaust portal 330 comprises a particle trap 342 to prevent particles generated by the dispenser 306 from reaching vacuum pumps and other processing equipment downstream of the chamber 302. The particle trap 342 may be any suitable device, such as a filter or vortex separator.

[0057] Figure 4 is a schematic cross-sectional view of an apparatus 400 according to another embodiment. The apparatus 400 is similar in most respects to the apparatus 300 of Figure 3. The apparatus 400 comprises a processing chamber 402, substrate support 404, and a dispenser 406, which in some embodiments may be a distributor that dispenses material according to certain desired patterns.

[0058] The dispenser 406 comprises an atomization chamber 408 and a nozzle 420, though which the atomized precursor mixture exits the dispenser 406. A first precursor mixture is provided to the atomization chamber 408 through a first source conduit 436 in fluid communication with a precursor source (not shown). The first source conduit 436 delivers the first precursor mixture to a flow controller 434, which controls flow of the first precursor through a first precursor delivery conduit 412 into the atomization chamber 408. An atomizing gas is generally blended with the first precursor mixture in the first precursor delivery conduit 412 The nozzle 420 carries the atomized first precursor mixture from the atomization chamber 408 through opening 418 to a energy input zone 422 near the end of the nozzle 420.

[0059] The energy input zone 422 may be an enclosure adjacent to the atomization chamber 408 or a confined space configured to direct the gas mixture in a desired pattern. In one example, a second precursor, which may comprise carbon, oxygen, or both, and may be a flammable gas mixture, is provided through an annular pathway 428 around the nozzle 420. The annular pathway 428 is configured to flow the second precursor into the atomized first precursor in a uniform manner as it exits the nozzle 420. As the precursor streams mix, the second precursor delivers energy into the atomized first precursor to create a solids stream comprising a mixture of the solutes in the first precursor. The precise geometry of the nozzle 420 and the mixing zone 422 may be adjusted to achieve any desired flow pattern or mixing method. As noted above in connection with Figure 2, the second precursor may also be a hot gas that is not flammable, such as hot air.

[0060] The second precursor is delivered to the mixing zone 422 by a second precursor source conduit 438 in fluid communication with a second precursor source (not shown). The second precursor flows through the flow controller 434 into a second precursor delivery conduit 414 to the annular pathway 428.

[0061] A third precursor may be delivered through a third precursor delivery conduit 416 flowing from a third precursor source conduit 440, in fluid communication with a third precursor source (not shown), through the flow controller 434. The third conduit 424 may have a distribution head configured to distribute the third precursor in a pattern that substantially overlaps the pattern of impact on the substrate by the nanocrystal stream, such that the nanocrystals are secured to the substrate by the third precursor. As with the apparatus 300 of Figure 3, if the apparatus 400 of Figure 4 is used as the first processing apparatus of the method 200, the third precursor is not provided to the apparatus 400.

[0062] In the apparatus of Figure 4, the dispenser 406 may move with respect to the substrate support 404 to form a film over all, or a substantial portion of, a substrate disposed on the substrate support 404. This may be accomplished by moving the dispenser 406, the substrate support 404, or both. For example, the dispenser 406 may be configured to extend and retract across the chamber 402 using an actuator. Alternately, or in addition, the substrate support 404 may have a positioning mechanism, such as a precision x-y stage, schematically represented at 444.

[0063] Exhaust gases leave the chamber 402 through an exhaust portal 430, which may have any convenient configuration. The portal 430 may be a single opening in a wall of the chamber 402, as shown in Figure 4, or multiple such openings, or a circumferential exhaust channel disposed around a circumference of the chamber 402. The exhaust portal 430 comprises a particle trap 442 to prevent particles generated by the dispenser 406 from reaching vacuum pumps and other processing equipment downstream of the chamber 402. The particle trap 442 may be any suitable device, such as a filter or vortex separator.

[0064] Figure 5A is a schematic view of an apparatus 500 for forming an electrochemical layer on a substrate. The apparatus 500 comprises a first processing stage 502, a collection stage 504, and a second processing stage 506. The first processing stage 502 may be a drying apparatus, and may comprise a thermal or plasma sprayer. The collection stage 504 collects material from the first processing stage 502 into a solids receptacle and feeds it to the second processing stage 506. The second processing stage 506, which may be a synthesis apparatus, dispenses material toward a substrate 508 to form an electrochemical layer thereon. The apparatus 500 may be used to perform the method 200 of Figure 2.

[0065] The first processing stage 502 comprises a first dispenser 510, a first precursor source 512, an atomizing gas source 514, and an energy component source 516. The first precursor source 512, atomizing gas source 514, and energy component source 516 may be similar to the first precursor described above in connection with Figure 2. The first dispenser 510 may be generally similar to either of the apparatus 300 or 400 of Figures 3 and 4. The first precursor source 502 is a liquid that is fed, along with the atomizing gas source 514, to a mixing location in the first dispenser 510, through an atomizing aperture or opening to an energy input location. The energy component source 516 is fed to the energy input location for mixing with the atomized first precursor source 502.

[0066] The first processing portion 502 dispenses a powder 518, formed from the first precursor, into the collection portion 504. The collection portion 504 comprises a collection apparatus 520, which may further comprise a solids receptacle 522 and a feeder 524. As described above in connection with Figure 2, the solids receptacle 522 may be a centrifugal separator, such as a cyclone, or a hopper, and may be electrostatically enhanced. For example, an outer wall of a cyclone separator may be energized with a weak DC voltage to encourage particles of the powder 518 to adhere to the walls, enhancing separation of the powder from the gas. Powder thus separated may be dropped into the feeder 524, or directly into a conduit to feed the second processing portion 506. As such, the collection apparatus 520 may consist of a separator, a feeder, or both.

[0067] Figure 5B is a cross-sectional view of a cyclone separator 522A according to another embodiment. The dispenser 510 is shown dispensing the powder 518 into a tangential feed point of the separator 522A. Solids are collected and exit the cyclone separator 522A through a solids exit portal 545 and the majority of gas exits through a gas exit portal 550. The solids exiting the cyclone separator 522A through the solids exit portal 545 may be collected in the feeder 524 of the collection stage 504.

[0068] Solids collected in the collection stage 504 are provided to the second processing portion 506 through a conduit 526. A gas may be blown through the conduit 526 to facilitate movement of the crystal powder into the second processing portion 506. The second processing portion 506 comprises a second dispenser 528, which may be generally similar to the apparatus 300 of Figure 3 or the apparatus 400 of Figure 4, and a third dispenser 536 for dispensing an additive for co-deposition with the electrochemical crystals 530 exiting the second dispenser 528. A precursor 540 for the additive is fed to the third dispenser 538. The third dispenser 538 is generally oriented to dispense the additive over the same area that the crystals 530 are deposited. Insertion of the additive stream into the crystal stream is selected, as described above, to remove a desired amount of liquid from the additive stream.

[0069] An energy producing precursor 532 and an oxygen containing precursor 534, are provided to the second dispenser 528 for forming the electrochemical crystals. The energy producing precursor 532 may be a plasma maintaining gas such as argon, helium, or hydrogen, or a flammable gas such as any of the hydrocarbons described above.

[0070] The apparatus 500 of Figure 5A features two decoupled processing stages for generating electrochemically active materials to deposit on a substrate. Although the electrochemical precursor solutions described above may be converted directly to electrochemically active materials in a single processing stage, dispenser design is complicated by handling a variety of precursors, additives, and energy providing precursors. Decoupling, for example by drying the electrochemical precursors in a first stage and synthesizing electrochemically active materials in a synthesis stage, reduces complexity of dispenser design and footprint of the apparatus.

[0071] While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof.