Environmental Humidity Energy Harvesters

Abstract

The solid-state energy harvester comprises an anode comprising a first transition metal suboxide, a cathode comprising a second transition metal suboxide, and a separator disposed between the anode and the cathode, wherein at least one of the anode, cathode, or separator contains water, and the harvester generates electricity when electrically connected to an external load.

Description

[Technical Field]

[0001] All references cited herein, including but not limited to patents and patent applications, are incorporated by reference in their entirety.

[0002] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority from U.S. Provisional Patent Application No. 63 / 414,161, filed October 7, 2022, which is incorporated herein by reference in its entirety. [Background technology]

[0003] (background) An energy harvester is a device that collects energy from the environment rather than storing it. See, for example, U.S. Patent Nos. 8,115,683, 10,147,863, 10,142,125, and 10,141,492. Energy harvesters collect energy from a variety of sources (e.g., solar, thermal, wind, salinity gradient, kinetic, piezoelectric, pyroelectric, thermoelectric, and RF harvesting devices such as crystal radios). Some generators are very high-power, such as wind and solar, while others are very low-power, such as piezoelectric and RF generators. However, these energy harvesters collect energy from the environment rather than storing it.

[0004] Recent efforts have been made to create batteries that use only electrons, rather than ions, to transfer charge. See Sigler, D., "All-Electron Battery—Stanford Strikes Again," CAFE Foundation (3 / 28 / 2015) (cafe.foundation / blog / electron-battery-stanford-strikes). However, these devices store energy rather than harvest it.

[0005] Therefore, there is a need for energy harvester devices that use solid electrolytes to generate energy on demand from the surrounding environment in a variety of applications.

[0006] All metal oxides have integer valences. Transition metal suboxides are metal oxides in which some of the oxygen atoms in the crystal structure are missing, making the valence of the metal atoms appear to be non-integer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 8,115,683 [Patent Document 2] U.S. Patent No. 10,147,863 [Patent Document 3] U.S. Patent No. 10,142,125 [Patent Document 4] U.S. Patent No. 10,141,492 [Non-patent literature]

[0008] [Non-Patent Document 1] Sigler, D., “All-Electron Battery-Stanford Strikes Again,” CAFE Foundation (3 / 28 / 2015) [Non-patent document 2] Hang et al., "The Role of Multiple Defects Correlated with a Single Oxygen or Metal-Induced Defect in the Formation of Conductive Filaments," Department of Precision Instruments, Brain-Inspired Computing Research Center, Tsinghua University, Beijing, China. [Non-patent document 3] Gellings et al., "Solid state aspects of oxidation catalysis," Institute of Inorganic Materials Science, University of Twente, PO Box 217, NL-7500 AE Enschede, The Netherlands (2000)

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Non-Patent Document 7

Summary of the Invention

Means for Solving the Problems

[0009] Embodiments described herein provide a solid-state energy harvester comprising: a first current collector comprising a conductor; a first layer comprising a first transition metal suboxide and a second transition metal suboxide, the first layer being an anode and in contact with the current collector; a second layer in contact with the first layer, the second layer being a separator; and a third layer comprising a third transition metal suboxide and a fourth transition metal suboxide, the third layer being a cathode and in contact with the second layer and the second current collector, the second layer forming a separator layer between the first layer and the third layer.

[0010] It should be understood that the solid-state energy harvesters described herein may be configured to store energy or may be combined with an energy storage device if desired.

[0011] A further embodiment provides a solid-state energy harvester comprising: a first current collector comprising porous carbon fibers, filaments, powder, or paper and a conductor; a first layer comprising a first transition metal suboxide and a second transition metal suboxide, the first layer being an anode and in contact with the current collector; a second layer in contact with the first layer, the second layer being a separator; and a third layer comprising a third transition metal suboxide and a fourth transition metal suboxide, the third layer being a cathode and in contact with the second layer and the second current collector, the second layer forming a separator layer between the first and third layers; wherein the solid-state energy harvester generates an electric current in the presence of oxygen and water vapor.

[0012] In another aspect, a method for manufacturing a solid-state energy harvester includes grinding an anode mix comprising a first transition metal suboxide, a second transition metal suboxide, and a binder; grinding a cathode mix comprising a third transition metal suboxide, a fourth transition metal suboxide, and a binder; adding and mixing carbon powder to each of the anode mix and cathode mix; forming the anode mix into a first layer, the first layer being the anode; forming a second layer, the second layer being the separator; forming the cathode mix into a third layer, the third layer being the cathode; and connecting the first layer to the second layer and the second layer to the third layer, wherein the first transition metal suboxide and the third transition metal suboxide are different from each other.

[0013] In some embodiments of the method, the anode mix and cathode mix are ground in a high-shear, high-intensity blender for at least 1 minute. The binder may comprise a Teflon binder, preferably poly(1,1,2,2-tetrafluoroethylene), with about 40 volume percent binder in each of the first and third layers. In some embodiments, the first, second, and third layers are compressed in a roller mill to form a back extrusion. The anode mix preferably comprises about 83% nTiO, 17% nWO. 2.9 , 40 volume percent binder (powder), and 2% nanosized acetylene carbon black powder, preferably Vulcan XC 72R or Nano307. In some embodiments, the cathode mixture comprises about 70% nWO 2.9 , 30% Co3O4, 40 volume percent binder (powder), and 2% nano-sized acetylene carbon black powder, preferably Vulcan XC 72R or Nano307. Alternatively, the cathode mixture may comprise about 72% nWO 2.9 and 28% Co3O4, 40 volume percent binder (powder). In some embodiments, the second layer comprises hydrated unplasticized cellophane and a proton exchange membrane, or hydrated unplasticized cellophane loaded with silver.

[0014] In some embodiments of this method, the anode mix is ​​about 83% nTiO, 17% nWO 2.9 , 40 volume percent binder (powder), and 2% nanosized acetylene carbon black powder, preferably Vulcan XC 72R or Nano307; the second layer comprises one of hydrated unplasticized cellophane and a proton exchange membrane; and the cathode mixture comprises about 70% nWO 2.9 , 30% Co3O4, 40 volume percent binder (powder), and 2% acetylene n carbon black (Cabot V72).

[0015] In another embodiment of this method, the anode mix is ​​about 83% nTiO, 17% nWO 2.9 , 40 volume percent binder (powder), and 2% nanosized acetylene carbon black powder, preferably Vulcan XC 72R or Nano307; the second layer comprises one of hydrated unplasticized cellophane or a proton exchange membrane; and the cathode mixture is about 72% nWO 2.9 , 28% Co3O4, 40 volume percent binder (powder), and 2% nano-sized acetylene carbon black powder (preferably Vulcan XC 72R or Nano307). The first and third layers preferably each comprise Teflon particles, the binder comprises a powder, and the first and third layers are each made using a roller mill to force the powder through the rollers of the mill and extrude the Teflon particles into fibrils. In one aspect of the method, forming the anode mix into the first layer includes forming an anode disk and grommet assembly. [Brief explanation of the drawings]

[0016] [Figure 1] An example of the crystal structure of cerium dioxide is shown below. [Figure 2] An example of the reduction mechanism of cerium is shown below. [Figure 3]Shows how oxygen dissolves in water. [Figure 4] The effect of dehydration on the crystal structure of tungsten suboxide WO2.9 is shown. [Figure 5] An exemplary crystal structure of cobalt suboxide (also known as cobalt(II,III) oxide (Co3O4)) is shown. [Figure 6] An example of the crystal structure of Ti4O7 is shown below. [Figure 7] Figure 7A shows an example physical layout of an embodiment of a solid-state energy harvester with multiple extended metal layers between the electrodes, and Figure 7B shows an example physical layout of a six-electrode energy harvester. [Figure 8] 1 illustrates a method for manufacturing rolled electrodes using a rolling mill. [Figure 9] 10 is a graph showing an example of current density when the energy harvester is short-circuited. [Figure 10] 10 is a graph illustrating an example of the recovery of an energy harvester after a short circuit. [Figure 11] 1 is a graph showing exemplary results of recording the open circuit voltage (OCV) of a non-discharging energy harvester in oxygen, argon (0% oxygen), and air after a short circuit. [Figure 12] 1 is a graph showing examples of short-circuit current density in air, oxygen, and argon (0% oxygen). [Figure 13] 1 is a graph showing an exemplary voltammogram of a dead short energy harvester after standing in air for 48 hours. [Figure 14] 1 is a graph illustrating AC impedance of an exemplary solid-state energy harvester. [Figure 15] 1 is a graph illustrating a Nyquist diagram of an exemplary solid-state energy harvester. [Figure 16] 1 shows an exemplary solid-state energy harvester with nickel expanded metal between all electrodes. [Figure 17] 1 is a graph showing a voltammogram of an exemplary solid-state energy harvester. [Figure 18]18A and 18B are graphs showing short circuit discharge and spontaneous recharge of an exemplary solid-state energy harvester, respectively. [Figure 19] FIG. 1 is a diagram of an exemplary three-layer thin film solid-state energy harvester. [Figure 20] 1 is a voltammogram of an exemplary solid-state energy harvester. [Figure 21] 1 is a graph illustrating the long-term open circuit voltage (OCV) of an exemplary solid-state energy harvester. [Figure 22] FIG. 1 is a cross-sectional view of an exemplary solid-state energy harvester. [Figure 23] 1 is a graph showing current density for three 24-hour tests of an exemplary solid-state energy harvester. [Figure 24] 1 is a graph showing OCV recovery after testing an exemplary solid-state energy harvester three times in various environmental gases, including air, oxygen, and the inert gas argon (0% oxygen). [Figure 25] 1 is a graph showing OCV during a test showing OCV recovery in three different gas environments (oxygen, air, and (0% oxygen)). [Figure 26] 1 is a graph illustrating dead short circuit discharge over the life of an exemplary solid-state energy harvester. [Figure 27] 1 is a graph showing the long-term discharge of a typical solid-state energy harvester over an 8-day period. [Figure 28] 10 is a graph showing the effect of adding oxygen or argon (0% oxygen) or air (20% oxygen) to a test chamber during energy harvester discharge for an exemplary solid-state energy harvester. [Figure 29] 1 is a graph showing impedance as a function of current density when humidifying an exemplary solid-state energy harvester to water saturation. [Figure 30] 1 shows limiting currents obtained from voltammograms of three exemplary energy harvester designs. [Figure 31]1 illustrates the general electron flow of an exemplary energy harvester. [Figure 32] An example of a three-layer cell design with an anode (A), separator (Sep), and cathode (C) is shown. [Figure 33] The power density curves for the open circuit voltage (OCV) recovery after 24 hours of short circuiting are shown for a three-layer cell design with graphite added to the anode and cathode, compared to a two-electrode design without graphite added to the anode and cathode. [Figure 34] The three-layer design with added carbon in the electrodes shows an approximately 10-fold increase in power density during complete short-circuit discharge compared to the two-layer design without added carbon in the electrodes. [Figure 35] Three carbon-added electrode designs are shown discharged to 100 mV in air, oxygen, argon, and argon for 24 hours. [Figure 36] The power curves for three exemplary designs are labeled: a two-electrode design with no carbon, a three-electrode design with 3% nanographite loading in the anode and cathode and an SSE layer between the anode and cathode, and a three-electrode design with 3% Vulcan 72 carbon black loading in the anode and cathode and an SSE layer between the anode and cathode. [Figure 37] 1 shows improved performance using an exemplary three-electrode design with gold-plated current collectors, nano-sized powders, and carbon additives. [Figure 38] The improvement in performance from the three-electrode design is shown in FIG. 37, which shows the first derivative of the polarization curve. [Figure 39] 1 shows the results of an exemplary experiment demonstrating the effect of relative humidity (RH) on current output. [Figure 40] 1 shows the cell-specific current densities of exemplary active components (Ti4O7 and Co3O4) with and without exemplary solid electrolyte (SSE) separators (CeO2 and WO2.9). [Figure 41] 1 shows the results of an exemplary study measuring cell power density as a percentage of maximum cell power for varying electrode thicknesses. [Figure 42] An example of a five-layer cell design is shown, with an anode, separator, and cathode within the cell body. [Figure 43] FIG. 1 is an elevation view of a polypropylene gasket used in the manufacture of an exemplary cell. [Figure 44] 3D CAD view of the tester holder used in the fabrication of an exemplary cell. [Figure 45] FIG. 45 is a cross-sectional view of the holder of FIG. 44. [Figure 46] 1 illustrates the chemical mechanism of an exemplary cell. [Figure 47] FIG. 22 shows an exploded view of the oxygen-free cell of Example 22. [Figure 48] FIG. 2 is a cross-sectional view of the oxygen-free cell of Example 22 after loose assembly. In use, the parts are compressed together. DETAILED DESCRIPTION OF THE INVENTION

[0017] The methods, compositions, and devices disclosed below can be described generally or specifically. It should be noted that when the description is specific to a particular embodiment, the embodiment does not limit the scope of the device or method. The features and essence of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0018] Embodiments described herein provide a solid-state energy harvester with a first current collector comprising a highly conductive solid sheet, such as gold-plated brass.

[0019] The first layer of the energy harvester comprises a first transition metal suboxide and a solid-state electrolyte (SSE), the first layer being an anode and in contact with a first current collector.

[0020] The second layer may comprise a mixture of a second transition metal suboxide and a lanthanide oxide or dioxide, the mixture forming a solid state electrolyte (SSE) and in contact with the first layer.

[0021] The third layer of the energy harvester may comprise a third transition metal suboxide, the third layer being the cathode and in contact with the second layer and a porous carbon fiber, filament, powder, or paper current collector.

[0022] The first transition metal suboxides are tungsten suboxide, cobalt suboxide, Na 1.0 Mo 1.5 WO 6.0 , Na 0.9 Mo6O 17 , Na 1.0 Ti 1.5 WO 4.5 , Na 1.2 Ti 0.34 WO4, Ti4O7, Ti5O9, K 1.28 Ti8O 16 , K. 1.04 Ti8O 16 , K. 0.48 Ti8O 16 , Na4WO3, Na 0.90 WO 1.81 , Na 0.82 WO 1.81 , Na 0.74 WO 1.81 , K. 0.9 WO3, WO 2.72 , WO 2.82 , WO 2.9 , Na2WO4, Na 8.2 WO, Na2O2WO3, Na 1.2 Ti 0.34 WO4, Na 1.2 Cu 0.31 WO 7.2 , Na 1.2 Mo 0.31 WO 5.2 and Na2O4WO3.

[0023] The third transition metal suboxides are tungsten suboxide, cobalt suboxide, Co3O4, Na 1.0 Mo 1.5 WO 6.0 , Na 0.9 Mo6O 17 , Na 1.0 Ti 1.5 WO 4.5 , Na 1.2 Ti0.34 WO4, K 1.28 Ti8O 16 , K. 1.04 Ti8O 16 , K. 0.48 Ti8O 16 , Na4WO3, Na 0.90 WO 1.81 , Na 0.82 WO 1.81 , Na 0.74 WO 1.81 , K. 0.9 WO3, WO 2.72 , WO 2.82 , WO 2.9 , Na2WO4, Na 8.2 WO, Na2O2WO3, Na 1.2 Ti 0.34 WO4, Na 1.2 Cu 0.31 WO 7.2 , Na 1.2 Mo 0.31 WO 5.2 and Na2O4WO3.

[0024] The energy harvester can be used to harvest ReO3, Na 0.9 WO3, Na 0.9 WO3 + TiO, Na 0.9 WO3+MoO2, Na 1.0 WO3, Na 1.1 WO3, Na 0.83 WO3, Ti4O7, Co3O4, CeO2, potassium titanate (K 1.28 Ti8O 16 ), KI, KCl, and other suboxides. The anode may optionally contain Na 0.9 W 0.75 Ti 0.25 03, and the cathode may optionally contain Na 0.9 W 0.75 Cu 0.25 F 0.3 O 2.8 may include:

[0025] The first transition metal suboxide, the second transition metal suboxide, or the third transition metal suboxide may be selected from the group consisting of boron, iron, copper, and nickel suboxides.

[0026] In a further embodiment, the first transition metal suboxide is an alkali metal suboxide (eg, rubidium and cesium suboxide).

[0027] The lanthanide oxide may be selected from the group consisting of cerium dioxide, lanthanum oxide or dioxide, praseodymium oxide or dioxide, neodymium oxide or dioxide, promethium oxide or dioxide, samarium oxide or dioxide, europium oxide or dioxide, gadolinium oxide or dioxide, terbium oxide or dioxide, dysprosium oxide or dioxide, holmium oxide or dioxide, erbium oxide or dioxide, thulium oxide or dioxide, ytterbium oxide or dioxide, and lutetium oxide or dioxide.

[0028] In yet another embodiment, the first transition metal suboxide is Ti4O7. In one embodiment, the second transition metal suboxide is WO 2.9 In another embodiment, the third transition metal suboxide is Co3O4. In a further embodiment, the first layer and the third layer are substantially free of noble metals.

[0029] In one embodiment, the first layer, second layer, and third layer each further comprise a binder (eg, unsintered Teflon (PTFE), FEP, paraffin, epoxy).

[0030] The anode may contain about 0.01% to about 14% water, and the cathode may contain about 0.01% to about 4% water.

[0031] In a further embodiment, the first transition metal suboxide, the second transition metal suboxide, and the third transition metal suboxide each have a stoichiometry M x-y and M is a transition metal M; x is the base valence of the transition metal M; y is the deviation from 1, when M is titanium, x is 4 and y is at least 0.5; When M is cobalt, x is 3 and y is at least 0.3; When M is tungsten, x is 5 and y is at least 0.2.

[0032] The conductor may comprise a metal comprising gold, nickel, copper, brass, bronze, or porous carbon fiber.

[0033] In one embodiment, the porous carbon fibers have greater than about 50% porosity, or greater than about 55%, 60%, or 65% porosity, and in other embodiments, the pores have diameters of about 10 μm to about 40 μm, or 15 μm to about 35 μm, or 20 μm to about 30 μm.

[0034] In a further aspect, the current collector comprises a metal foam.

[0035] In one embodiment, a solid-state energy harvester includes a first current collector containing a conductor, a first layer comprising a first transition metal suboxide and a second transition metal suboxide, the first layer being the anode and in contact with the current collector, a second layer in contact with the first layer, the second layer being a separator comprising cellulose, a third layer comprising a third transition metal suboxide and a fourth transition metal suboxide, the third layer being the cathode and in contact with a second current collector comprising porous carbon paper in contact with the second and third layers, and a fine stainless steel screen in contact with the porous carbon paper to form the second (cathode) current collector. Preferably, the first transition metal suboxide comprises Ti4O7 and the second transition metal suboxide is WO 2.9 the third transition metal suboxide comprises Co3O4, and the fourth transition metal suboxide comprises WO 2.9 The second layer is made of hydrated unplasticized cellophane and a proton exchange membrane, or silver-loaded hydrated unplasticized cellophane, or Nafion (formula CHF 13The solid-state energy harvester may comprise a sulfonated tetrafluoroethylene-based fluoropolymer copolymer represented by OS·C₂F₄. Preferably, the thickness of at least one of the first and third layers is about 0.25 mm to about 1 mm, more preferably about 0.7 mm. The conductor preferably comprises gold, nickel, copper, brass, bronze, or porous carbon fiber. The current collector preferably comprises a metal foam. In one embodiment, the solid-state energy harvester generates electric current in the presence of oxygen and water vapor. In one embodiment, the second current collector comprises a stainless steel screen. In one embodiment, the harvester takes the form of a cell assembly including a cathode current collector, a cathode disk and grommet assembly, a cellulose disk, an anode disk and grommet assembly, and a layer of gold-plated brass disks.

[0036] Embodiments described herein provide a solid-state energy harvester system including a first energy harvester and a second energy harvester. The first energy harvester and the second energy harvester comprise solid-state energy harvesters described herein, and a first layer of the first energy harvester is electrically connected to a third layer of the second energy harvester. The first layer of each of the first and second energy harvesters may comprise titanium suboxide, and the third layer of each of the first and second energy harvesters may comprise cobalt suboxide.

[0037] A further embodiment provides a solid-state energy harvester comprising: a current collector comprising a solid metal current collector (e.g., gold-plated); a first layer comprising a first transition metal suboxide and a solid-state electrolyte (SSE), the first layer being the anode and in contact with the current collector; a second layer comprising a mixture of a second transition metal suboxide and a lanthanide oxide or dioxide, the mixture forming an SSE and in contact with the first layer; and a third layer comprising a third transition metal suboxide, the third layer being the cathode and in contact with the second layer, the anode, and the current collector comprising porous carbon fiber, filament, powder, or paper, the solid-state energy harvester generating an electric current in the presence of oxygen and water vapor.

[0038] In one aspect, exposing an exemplary solid-state energy harvester to water vapor and / or elevated relative humidity (RH) may increase the current density generated by the exemplary solid-state energy harvester. In contrast, it is believed that liquid water may decrease the current density generated by the exemplary solid-state energy harvester. In some cases, the solid-state energy harvester may include an internal water supply configured to increase the relative humidity surrounding the solid-state energy harvester.

[0039] Without being bound by any particular theory, it is believed that the dissociation of water molecules adsorbed on the surface results in the formation of hydroxyl groups (OH-) and protons (H + ) is generated, and the proton is thought to be the internal charge transfer element.

[0040] In one embodiment, the anode electrochemical flow is HO+TiO x →TiO x OH - +H + →TiO x +1 / 2O2+H + +2e - , or simply HO-TiO x →1 / 2O2+2H + +2e - In this manner, the electrons travel through an external circuit to the cathode.

[0041] In one embodiment, the cathode electrochemical flow is 2CoOx+2H + +2e - →2CoO x +H2, or simply 2H + +2e - -CoO x →H2 is obtained.

[0042] Without being bound by any particular theory, it is believed that an exemplary solid-state energy harvester may extract oxygen from the anode and hydrogen from the cathode.

[0043] In one aspect, the moisture absorption of exemplary compounds used in solid-state energy harvesters is CoO2>Ti4O7>>Co3O4>WO 2.9 is.

[0044] In some cases, the first transition metal suboxide comprises TiO, the second transition metal suboxide comprises CoO, and the SSE comprises CeO and WO. 2.9 Equipped with.

[0045] In some cases, at least one of the first layer, second layer, and third layer has a thickness of from about 0.25 mm to about 1 mm.

[0046] In some cases, the thickness of at least one of the first layer, second layer, and third layer is about 0.7 mm, alternatively between 0.5 mm and 0.9 mm, or between 0.6 mm and 0.8 mm.

[0047] In some embodiments, the current density generated by the solid-state energy harvester at 85% relative humidity is 45%-55%, or about 50%, of the maximum current density at 100% RH.

[0048] Also provided is a method for manufacturing a solid-state energy harvester. An exemplary method includes the steps of: (1) grinding a solid electrolyte (SSE) comprising a lanthanide, a second transition metal suboxide, and a binder; (2) grinding an anode mixture comprising a first transition metal suboxide, the SSE, and the binder; (3) grinding a cathode mixture comprising a third transition metal suboxide, the SSE, and the binder; (4) adding and mixing carbon powder to each of the anode mixture and the cathode mixture; and (5) grinding a cathode mixture comprising a lanthanide, a second transition metal suboxide, and the binder. (6) forming the anode mixture in a first layer, the first layer being the anode; (7) forming the SSE mixture in a second layer, the second layer being the SSE separator; (8) forming the cathode mixture in a third layer, the third layer being the cathode; and (9) connecting the first layer to the second layer and the second layer to the third layer, wherein the first transition metal suboxide, the second transition metal suboxide, and the third transition metal suboxide are different from one another.

[0049] Without being bound by any particular theory, it is believed that milling steps (2) and (3) followed by step 4 (mixing in carbon powder) unexpectedly improves performance, as described in Example 13 and the accompanying figures.

[0050] In all embodiments of the present invention, the carbon content can vary, but is preferably 1-10%, more preferably about 5%. The carbon used is preferably nano-sized acetylene carbon black powder.

[0051] The first transition metal suboxide and the second transition metal suboxide are tungsten suboxide, cobalt suboxide, Co3O4, Na 1.0 Mo 1.5 WO 6.0 , Na 0.9 Mo6O 17 , Na 1.0 Ti 1.5 WO 4.5 , Na 1.2 Ti 0.34 WO4, Ti4O7, Ti5O9, K 1.28 Ti8O 16, K. 1.04 Ti8O 16 , K. 0.48 Ti8O 16 , Na4WO3, Na 0.90 WO 1.81 , Na 0.82 WO 1.81 , Na 0.74 WO 1.81 , K. 0.9 WO3, WO 2.72 , WO 2.82 , WO 2.9 , Na2WO4, Na 8.2 WO, Na2O2WO3, Na 1.2 Ti 0.34 WO4, Na 1.2 Cu 0.31 WO 7.2 , Na 1.2 Mo 0.31 WO 5.2 and Na2O4WO3.

[0052] In another embodiment, the anode mix, SSE mix, and cathode mix are ground in a high shear, high intensity blender for at least 1 minute.

[0053] In a further embodiment, the first, second, and third layers are not separated by a physical separator. The first transition metal suboxide and the third transition metal suboxide may each be selected from the group consisting of titanium, cobalt, tungsten, or cesium. The first transition metal suboxide may comprise a titanium suboxide. In another embodiment, the water content of each of the anode mix and the SSE mix is ​​less than about 25 weight percent.

[0054] The second transition metal suboxide may comprise a cobalt suboxide.In a further embodiment, the first layer, second layer, and third layer each have a water content of less than about 5% by weight.

[0055] The first layer, the second layer, and the third layer can each comprise a solid electrolyte including tungsten suboxide and cerium dioxide. In a further embodiment, the anode mix, the SSE mix, and the cathode mix each have a water content of less than about 10 wt%.

[0056] The binder may be selected from the group consisting of unsintered polytetrafluoroethylene (PTFE), FEP, paraffin, and epoxy. In one embodiment, the binder is less than about 50 volume percent of each of the first layer, the second layer, and the third layer.

[0057] In yet another embodiment, the first layer, the second layer, and the third layer are compressed in a roller mill to form a back extrusion. In this embodiment, the solid-state energy harvester may optionally not contain a physical separator between the first layer and the second and third layers.

[0058] In one embodiment, the anode mix is ​​about 17% (w / w) CeO, 33% (w / w) WO 2.9 , 50% (w / w) Ti4O7, and 40 volume percent powdered PTFE.

[0059] The cathode mixture was approximately 17% (w / w) CeO2, 33% (w / w) WO 2.9 , 50% (w / w) Co3O4, and 40 volume percent powdered PTFE.

[0060] In one embodiment, the anode mix is ​​about 17% (w / w) CeO, 33% (w / w) WO 2.9 , 50% (w / w) TiO and 40% by volume of powdered PTFE, and the solid electrolyte mixture was approximately 67% (w / w) WO 2.9 , 33% (w / w) CeO2, and 40% by volume of powdered PTFE, and the cathode mixture was approximately 17% (w / w) CeO2, 33% (w / w) WO 2.9 , 50% (w / w) Co3O4 and 40% by volume of powdered PTFE.

[0061] In another embodiment, the first layer, second layer, and third layer each comprise Teflon particles, the binder comprises a powder, and each of the first layer and second layer is made by using a roller mill to force the powder through the rollers of the mill to extrude the Teflon particles into fibrils.

[0062] The solid-state energy harvester may optionally be housed in a non-conductive, substantially gas-impermeable housing, which may have a gas inlet and a gas outlet on opposite sides of the non-conductive, substantially gas-impermeable housing.

[0063] In a further aspect, the electrically non-conductive, substantially gas impermeable housing is made from polyacrylate or polycarbonate.

[0064] (Transition Metal Suboxides and Defect Theory) The general theory described herein is that typical active components of energy harvesters, such as Ti4O7, WO 2.9 , Co3O4, and CeO2. Nonstoichiometric metal oxide suboxides, called Magneli phases, have low band gaps and resistivities and exhibit the highest electrical conductivity. These phases have high oxygen vacancies, and electronic coupling increases with increasing oxygen vacancies. Electrons in the d orbitals split into two components with different energies: t2g and eg orbitals. The electronic conduction pathway can be switched by the drift of charged oxygen vacancies. Conductivity in the conduction band can be the result of either these oxygen vacancies and / or metal-induced defects. The low stoichiometry has been suggested to result from either oxygen vacancies or metal interstitials, which are represented by the following two redox reactions in the Kroger-Vink notation: [ka]

[0065] See, for example, Zhang et al., "The Role of Multiple Defects Correlated with a Single Oxygen- or Metal-Induced Defect in the Formation of Conductive Filaments," Department of Precision Instruments, Brain-Inspired Computing Research Center, Tsinghua University, Beijing, China (Non-Patent Document 2), the entire text of which is incorporated herein by reference.

[0066] Using these reaction equations, the charge transfer reactions can be individually described as follows: O x o+ h · →O · 0

[0067] where O x o represents a neutrally charged oxygen ion located at an oxygen lattice site, h represents an electron hole, and O0 represents a singlet oxygen atom with a single charge. Ce x ce +e - →Ce ’ ce’ is.

[0068] Here, Ce x ce indicates a cerium ion located at a cerium lattice site and having a neutral charge, and Ce ’ ce’ indicates a single negatively charged cerium anion located in an interstitial site.

[0069] This is an exemplary illustration of how a cerium ion located at a neutrally charged cerium lattice site can accept an electron and become a charged cerium ion on that lattice site, and how charge is transferred within the solid electrolytes described herein.

[0070] See also Gellings et al., "Solid state aspects of oxidation catalysis," Institute of Inorganic Materials Science, University of Twente, PO Box 217, NL-7500 AE Enschede, The Netherlands (2000), incorporated herein by reference in its entirety.

[0071] In the case of a proton defect in an oxide, an exemplary formation reaction between a water molecule and an oxygen vacancy is as follows: [ka]

[0072] This reaction creates two net positive hydroxyl groups in the usual oxygen atom positions. Other defect reactions, where proton defects are formed by reaction with hydrogen, are discussed below. Reactions with holes are as follows: [ka] Here, the presence of excess holes is required. Alternatively, the oxidation of hydrogen with the production of free electrons is shown in the following reaction: [ka] Assume that the electrons are donated to the conduction band.

[0073] Gellings et al. propose that at low temperatures, the dissolution of water in the Li / MgO catalyst occurs by reaction with oxygen or oxygen vacancies, as shown in the following reaction equation: [ka]

[0074] At low temperatures (e.g., 673 K), conductivity is found to be driven by OHO ions acting as the primary charge carriers, indicating that water plays an important role in charge transport in both the Ti4O7 anode and the CeO2 solid "electrolyte."

[0075] It is theorized that CeO2 can store and transport oxygen and, under reduced conditions, splits water to release hydrogen as shown in the following reaction equation (see B. Bulfin et al., "Analytical Model of CeO2 Oxidation and Reduction," School of Physics, Trinity College Dublin, College Green, Dublin 2, Ireland, J. Phys. Chem. C, 2013, 117(46), pp. 24129-24137, DOI: 10.1021 / jp406578z, Published (Web): October 16, 2013 (Non-Patent Document 4), which is incorporated herein by reference in its entirety): [ka]

[0076] Bulfin et al. describe the relationship between cerium dioxide and its suboxide state and the resulting activity of these molecules. This is primarily relevant to the production of synthetic fuels and catalytic converters. The relationship described by Bulfin et al. uses the Arrhenius equation, which shows that the rate constant for most chemical reactions increases proportionally to the negative power of the reciprocal of absolute temperature. According to Bulfin et al., this effect is apparent above 500 °C. However, many of Bulfin et al.'s graphs show that some activity occurs even at room temperature.

[0077] In one embodiment, the solid-state energy harvesters described herein perform well up to about 90° C. in the presence of at least about 85% relative humidity.

[0078] One embodiment of the energy harvester described herein is a WO 2.9, CeO2, Co3O4, Ti4O7, and unsintered PTFE powder. Table 1 below shows the composition of an exemplary embodiment, where percentages are by weight and the PTFE binder is by volume. Components 1 and 2 in Table 1 are components of the solid electrolyte (SSE), component 3 is the active component of the anode, and component 4 is the active component of the cathode. PTFE is the binder. The three electrodes shown in Table 1 comprise a titanium-containing anode, a separator, and a cobalt-containing cathode. Moisture values ​​were measured and percentages determined based on the results of multiple factorial experiments shown in Table 1. Omitting the "separator" layer from the design results in a two-electrode design.

[0079] [Table 1]

[0080] In one embodiment, cerium dioxide (CeO2) and tungsten suboxide are used as the solid electrolyte. In this embodiment, the tungsten suboxide is WO 2.9 In this embodiment, these components are 2 parts CeO to 1 part WO 2.9 It exists in a ratio of 2 parts.

[0081] Cerium dioxide is a large molecule (MW=172.12) with oxygen atoms outside the crystal structure. The oxygen atoms are loosely bound, allowing them to move easily from one molecule to the next. Figure 1 shows a cerium atom 101 and an oxygen atom 102. Without being bound by any particular theory, it is believed that the difference in atomic size between the cerium atom 101 and the oxygen atom 102 allows the oxygen atoms to move relatively freely, allowing them to catalyze redox reactions. Figure 1 shows how loosely bound the oxygen atoms are in the large lanthanide cerium.

[0082] In another embodiment, the energy harvester contains a low percentage of water. Neutral water is the H + ions and OH - The molar concentration of the ion is 1x10 -7and is expressed as follows: H2O→H + +OH - 2H2O → 2H2 + O2

[0083] As reported by Zhang et al., CeO2 can catalyze this reaction. Without being bound to any particular theory, the following two mechanisms may be relevant:

[0084] (Mechanism 1) The use of CeO2 as a catalyst with transferable oxygen atoms is described in an article on truck catalytic converters, "Structural, redox and catalytic chemistry of ceria-based materials," G. Ranga Rao et al., Bulletin of the Catalysis Society of India (2003) 122-134 (Non-Patent Document 5), which is incorporated herein by reference in its entirety. CeO2 is used as a catalyst in various pollutant purification catalysts, including the conversion of methane gas to CO2 and water.

[0085] The following reaction equation (201 = Ce4+, 202 = O2-, 203 = vacancy, 204 = Ce3+, as shown in Figure 2) shows the steps of the process, where V = vacancy. H2+Ce +4 4O -2 4←Step 1→Reaction 3 Ce +4 4O -2 4H2 ← Step 2 → Reaction 4 Ce +4 2Ce +3 2O -2 3H + V+OH - ←Step 3→Reaction 5 Ce +4 2Ce +3 2O -2 3V + H2O ← Step 4 → Reaction 6 Ce +4 2Ce +3 2O -2 3V Reaction 7 Overall reaction: H2+Ce +4 4O -2 4 → Ce +4 2Ce +3 2O -2 3V Reaction 8

[0086] (Mechanism 2) Cerium dioxide (CeO2) is known for its oxygen transfer properties. CeO2 undergoes rapid redox cycling, e.g., 2CeO2 → Ce2O3 + 1 / 2O2 Reaction 9 Ce +4 →Ce +3 Eo=1.61 Cerium dioxide is Ce +4 / Ce +3 It functions as an oxygen buffer by absorbing and releasing O2 through a redox reaction. This is a reversible reaction, so it functions as an oxygen storage material. In the absence of oxygen (e.g., under an argon atmosphere), the reaction proceeds in the opposite direction. This promotes other electrode reactions with Ti4O7 and Co3O4, which are described below.

[0087] Without being bound by any particular theory, the actual mechanism may be a combination of the two pathways mentioned above and the "deficiency theory" explained above.

[0088] (point of zero charge) In one embodiment, the selected suboxides used in the anode and cathode have well-separated points of zero charge (PZC) (e.g., greater than 1, between 1 and 4, 1.5). PZC refers to the pH established when adsorbed water dissociates. Without being bound by theory, it is believed that this imbalance causes a potential difference between the electrodes. See, for example, Parks et al., "The Zero Point of Charge of Oxides," MIT, 1961 (Non-Patent Document 6); and "Surface charge characterization of metal oxides by potentiometric acid-base titration, revisited theory and experiment," Ma'rta Szekeres and Etelka Tomb a'cz, Department of Physical Chemistry and Materials Science, University of Szeged, Aradi vt. 1, 6720 Szeged, Hungary, 2012 (Non-Patent Document 7).

[0089] (Interaction between dissolved oxygen and water) In another embodiment, the energy harvester preferably contains a small amount of water within the electrodes and responds to the presence of oxygen, or conversely, the removal of oxygen with argon (0% oxygen). Oxygen does not ionize when dissolved in water but is instead held between water molecules, as shown in Figure 3, where the squares 301 represent water molecules (oxygen 102, hydrogen 302) and do not represent entities themselves. The oxygen molecules (303) become intimately involved in holding the diatomic oxygen molecules and thus transporting them from location to location. In a conventional energy harvester, this would be considered the "electrolyte," but in the energy harvester of the present invention, the electrodes are separated by nickel-expanded metal, so charge transport occurs within the electrodes, not between them. Combined with the understanding in the previous paragraph regarding defects in the suboxide crystal structure, one aspect of charge transport is the free flow of charge through the relatively small amount of water.

[0090] In certain embodiments, the anode may contain 0.01% to 15% water. In other embodiments, the anode may contain 0.1% to 10%, 1% to 8%, or 2% to 5% water. In certain embodiments, the second layer may contain 0.01% to 8% water. In other embodiments, the second layer may contain 0.1% to 5%, 1% to 4%, or 2% to 3% water. In certain embodiments, the cathode may contain 0.01% to 5% water. In other embodiments, the cathode may contain 0.1% to 10%, 1% to 8%, or 2% to 5% water.

[0091] In one embodiment, a WO 2.9 The interlayer, consisting of cerium dioxide and tungsten suboxide (WO), allows for the transfer of charge (presumably to oxygen atoms). 2.9 ) are mixed, in one example in equal weight ratios. Tungsten has many oxidation states, with +6 and +4 being the most stable. WO 2.9 makes the valence of tungsten +5.8, which is the average for the entire crystal. 2.9 is available from Global Tungsten (gobaltungsten.com).

[0092] Figure 4 shows the WO 2.9 The crystal structure of WO3 and the effect of dehydration on charge transport are shown. The octahedron shown in 401 represents the orbital field of tungsten, the large black dots 301 represent water molecules, the small black dots 102 represent singlet oxygen in the crystal, and the small light dots 302 represent hydrogen atoms. Without being bound by any particular theory, it is believed that the water molecules shown in Figure 4 allow more movement of the WO3 crystal components. WO x (WO 3-x The same structure exists for "a" (also referred to as "a"), but some of the charge-carrying oxygen is missing from the crystalline mass. Figure 4 shows the effect on the crystal structure as the crystal dehydrates from "a" containing sufficient water molecules 301, to "b" (slightly dehydrated), and finally to "c" (fully dehydrated). In one embodiment, the energy harvester is fabricated in the dehydrated "c" state and then spontaneously hydrated in situ from "b" to "a."

[0093] The following reaction scheme is an example. reduction ("V" = "vacancy") 2(W +6 -OW +6 )+4e - +O2 → Reaction 10 2(W +5 -VW +5 )2(O) + 4e → Reaction 11 2(W +5 -OW +5 )+4e - Reaction 12 Overall reaction: 2(W +6 -OW +6 )+O2→2(W +5 -OW +5 )+2e - oxidation 2(W +5 -OW +5 ) + O2 → Reaction 13 2(W +6 -OW +6 ) + (O) + 2e → Reaction 14 2W +5 +O2 → Reaction 15 (W +6 -OW +6 )+(O)+2e - Reaction Scheme 16 W +6 →W +4 (W +6 →W +5 Unknown) E o ~+ / -0.91 Volts E o Information source: http: / / hyperphysics.phy-astr.gsu.edu / hbase / Chemical / electrode.html Total: 2(W +5 -OW +5 )+O2→2(W +6 -OW +6 )+2(O)+2e - Reaction Scheme 17 Overall reaction equation of the separator reaction 2(W +6 -OW +6 )+O2←H2O →2(W +5 -OW +5 )+2e - Reaction Scheme 18 and 2(W +5 -OW +5 )+O2← H2O →2(W +6 -OW +6 )+2(O)+2e - Reaction Scheme 19 and 2Ce2O3+2O -2 ← H2O →4CeO2+4e - Reaction Scheme 20

[0094] In one embodiment, oxygen enters the separator and both singlet oxygen and electrons exit and migrate to the anode. In this embodiment, the singlet oxygen reacts with cerium oxide, transferring more electrons. Water can play a catalytic role in these reactions.

[0095] In one embodiment, the active component of the cathode is cobalt(II,III) suboxide (Co3O4). Figure 5 shows the crystal structure of Co3O4. +2 is spherical #2 (501), Co +3 The cobalt is shown as sphere #3 (502), and the oxygen atoms are shown as light-colored sphere #1 (202). Cobalt has two oxidation states, +2 and +3, and both are present in this crystal. The oxygen atoms are loosely bonded to the larger cobalt atoms, making them electronegative compared to the TiO anode. When CeO2 is mixed with CoO3, the charged oxygen atoms disperse, reducing the cobalt valence from +2 and +3 in CoO3 to only +2 in CoO, releasing the oxygen atoms into the oxygen pool bound to CeO2.

[0096] As a result of the above reaction, the CeO2-Co3O4 microcrystals undergo a reversible oxidation-reduction reaction, releasing or absorbing oxygen depending on the direction of the oxygen concentration, which is shown by the following radical reaction equation: O2+4e - →2O -2 Reaction Scheme 19 2Co3O4 → 6CoO + O2 Reaction Equation 20 The overall reaction equation for these two reactions is (Co +2.67 ←→Co +2 cations reduced at the cathode via 2Co3O4+4e - →6CoO+O -2 Reaction Scheme 21 From Equation 9 above: 2CeO2 → Ce2O3 + 1 / 2O2 Reaction 9 The overall reaction equation for Equation 21 and Equation 9 is: Co3O4+4e - +2CeO2 → 3CoO+O -2 +Ce2O3+1 / 2O2 Reaction 22 Looking at just the cations: Co +2.67 +Ce +4 →Co +2 +Ce +3 +1.76e - E o Approximately 1.715

[0097] The above is an example of how oxygen atoms can carry a charge and move freely from one cation to another in the manner described herein.

[0098] In one embodiment, the active component of the anode is Ti4O7 (Ti n O 2n-1 (also written as Ti) where n is 4 to 10. n O 2n-1 TiO7 is a type of non-stoichiometric titanium oxide known as the Magneli phase, which exhibits low band gap and resistivity and is the most electrically conductive phase reported for TiO7. The atomic structure of this molecule is shown in Figure 6, where the titanium atoms (601-604) in the TiO7 molecule are labeled "Ti1" through "Ti4," and the oxygen atom is labeled "O" (102). In TiO7, titanium has a valence of +3.5, which is the average value for the crystal, since valences must be integers. As electrons flow through the separator, the TiO7 molecules pass them to the anode conduction band in the Magneli phase and then to the anode current collector.

[0099] These reactions can be summarized as follows: H2O→H + +OH - Reaction Scheme 23 4Ti2O3+2OH - +2O -2 →2Ti4O7+H2O+2e - Reaction Scheme 24 Equation 9 above (expressed in anodic form): Ce2O3+1 / 2O2→2CeO2 Reaction 9 The overall reaction scheme for Equation 12 and Equation 9 is: 4Ti2O3+2OH - +O -2 +2Ce2O3+O2→2Ti4O7+H2O+4CeO2+2e - Reaction Scheme 24 Looking at just the cations: Ti +3 +Ce +4 →Ti +3.5 +Ce +3 E o Approximately 1.085 Complete Energy Harvester Flow: Cathode: CoO 4+ 2e - +4CeO2 → 3CoO + 2Ce2O3 + O2 + 1 / 2O2 Anode: 4Ti2O3+2OH - +O -2 +2Ce2O3+O2→2Ti4O7+H2O+4CeO2+2e - Overall: Co3O 4+ 4CeO2+4Ti2O3+2OH - +2H + +1 / 2O2+2Ce2O3→3CoO+2Ce2O3+2Ti4O7+2H2O+4CeO2 Thus, oxygen and water (dissociated) enter the cathode, the final acceptor for oxygen is the hydroxide ion, and water vapor is produced.

[0100] Table 2 below shows the associated potentials, which are similar to those observed in OCV experiments such as those shown in FIG.

[0101] [Table 2]

[0102] (Source of materials used) Ti4O7, Ti-Dynamics Co.Ltd, Magneli Phase Titanium Oxide-N82, www.Ti-dynamics.com.

[0103] Nano WO 2.9 , "Tungsten Blue Oxide" http: / / globaltungsten.com #P005016

[0104] Co3O4 Cobalt(II,III) Oxide, www.fishersci.com # AAA1612130

[0105] CeO2 Cerium(IV) Oxide, www.fishersci.com #AC199125000

[0106] Teflon 30 Dispersion "DISP30," www.fishersci.com #501090482 or www.chemours.com

[0107] PTFE 7CX: www.chemours.com

[0108] DAIKIN F104 Non-Sintered Teflon Powder

[0109] CABOT Vulcan XC72R (GP-3875) Carbon V72

[0110] ASBURY Graphite Mills “Nano307”

[0111] Crossbond Expanded Metal 4Ni 5-060 P&L x 4: Dexmet Corporation, 22 Barnes Industrial Rd S, Wallingford, CT 06492 (www.dexmet.com)

[0112] Nickel 10 mil shim stock, (www.mcmaster.com) #9707K79

[0113] 3 / 4 inch Silver Bezel: (www.riogrande.com) #950272

[0114] 24kt Gold Cyanide Plating Solution: (www.riogrande.com) #335082

[0115] 24kt gold sheet for anode: (www.riogrande.com) #608030

[0116] Durston rolling mill (www.durston.co.uk,#DRM F130R)

[0117] (Example 1: Pellet electrode) The pellet electrode is fabricated as follows.

[0118] Weighing powders; anode: 17% CeO2, 33% WO x , 50% Ti4O7, solid separator is 33.3% CeO2, 66.7% WO x , the cathode is 17% CeO2, 33% WO x , 50% Co3O4, and the binder is 40% by volume of Teflon 7c.

[0119] Mix the powders in a high-power blender. Prepare a 3 / 4-inch compression cylinder and lubricate it with a small amount of Ausimont Polymist F-5AEx sintered Teflon powder. Place 3 / 4-inch cross-bonded expanded metal discs (Dexmet Corp, 4Ni 5-00 P&L x 4) at the bottom of the compression cylinder. Pour the mixed powder into the cylinder. Layer another 3 / 4-inch cross-bonded expanded metal disc on top of the powder. Place a stainless steel cover plate on top of the cylinder. Compress to 5,000 lbs (11,318 psi) and hold for a few seconds. Remove from the cylinder and measure and record the weight and thickness.

[0120] Since the densities of all components are known, the weights and volumes are used to calculate the porosity of the resulting pellets. The pressure is chosen to provide good binding of the powders and good porosity. In this example, 5,000 pounds was found to be an appropriate pressure.

[0121] The pellets are then placed in a humidity chamber at 100% relative humidity for 4 days, resulting in an internal water content of approximately 5% in the anode, 3.5% in the separator, and 0.6% in the cathode.

[0122] Figure 7A shows the physical layout of one example of the resulting energy harvester with three electrodes: an anode pellet (7A1), a separator pellet (7A2), and a cathode pellet (7A3), with nickel cross-bonded expanded metal (7A6) between each layer, and the anode encased in a gold bezel (7A4) secured in place with epoxy adhesive (7A5). Each pellet also has nickel expanded metal (7A6) on each surface.

[0123] The separator pellet (7A2) is often omitted from the design, resulting in a two electrode design.

[0124] Example 2A: Rolled Electrode An embodiment of the rolled electrode is made as follows.

[0125] Weighing powders; anode: 17% CeO2, 33% WO x , 50% Ti4O7, solid separator is 33.3% CeO2, 66.7% WO x , the cathode is 17% CeO2, 33% WO x , 50% Co3O4, binder is 40% by volume Teflon 7c. Mix in a high-power blender.

[0126] Adjust the gap of a 60 mm diameter precision rolling mill (manufactured by Durston, www.durston.co.uk, #DRM F130R) to 0.178 mm (0.007 in). The rolls must be highly parallel. With the rollers in a horizontal position, pour the powder into the roller nip. Slowly rotate the rollers toward the nip, drawing the powder into the nip and forming a free-standing sheet behind the roller. Remove the sheet and place it on a clean piece of paper. Cut each sheet into a disc using an arch punch (e.g., McMaster Carr 3 / 4 inch (19 mm) diameter punch #3427A19). In one example, the cathode is 1 inch in diameter, the separator is 7 / 8 inch in diameter, and the anode is 3 / 4 inch in diameter to ensure no short circuits between the electrodes. In more precise manufacturing processes, these diameters can be the same.

[0127] The cathode sheet is placed on top of a current collector (e.g., gold, gold-plated nickel, or other metal). An in-electrode current collector may or may not be used on top of this first sheet. If an in-electrode current collector is used, 10 mil nickel shim stock, flat nickel expanded metal, or no spacer (sheets in direct contact) may be used. Following the protocol used for the current collector, next place a separator sheet, then the anode sheet. Place the current collector on top of the anode.

[0128] The resulting energy harvester is assembled into a test fixture, for example, by compressing it with a force of 40 psi.

[0129] Figure 7B shows the physical layout of a three-electrode, thin-rolled energy harvester. No metal spacers are used in this example. In Figure 7B, there is an anode layer 7A1, an anode layer 7A2, a separator layer 7A2, and a cathode layer 7A3 sandwiched between an anode current collector 7B1 and a cathode current collector 7B2. These energy harvester examples do not include an insulating separator, as do most liquid electrolyte energy harvesters.

[0130] The separator layer 7A2 is often omitted from the design, resulting in a two electrode design.

[0131] Example 2B: Rolled Electrode To solve the roller sticking problem described above, another embodiment of the rolled electrode was constructed as follows.

[0132] Weighing powders; anode: 17% CeO2, 33% WO x , 50% Ti4O7, solid separator is 33.3% CeO2, 66.7% WO x , the cathode is 17% CeO2, 33% WO x , 50% Co3O4, binder is 40% by volume Teflon 7c. Mix in a high-power blender.

[0133] A 60 mm diameter Durston precision rolling mill (www.durston.co.uk, #DRM F130R) (801 in Figure 8) is placed in a vertical position (801). Two pieces of sintered Teflon sheet (McMaster Carr #8545K13) at least 1 / 16 inch (1.58 mm) thick are cut (802) to approximately 100 mm (approximately 4 inches) wide and 150 mm (approximately 6 inches) long. The gap of the roller mill is adjusted to twice the thickness of the Teflon sheet plus 0.007 inches (0.178 mm). Alternatively, the rollers can be compressed together air-pressured rather than using a constant gap. This method allows for greater variation in the thickness of the powder fed into the mill than using a constant gap. A pair of 4 inch pancake cylinders (Mead Fluid Dynamics SS-400X1.125-FB) is used, generating 1257 lbs of force at 50 psi. A pressure of about 25 psi (630 pounds force) can produce a strong sheet while maintaining porosity in a useful range (eg, 0% to about 50% porosity).

[0134] The well-mixed powder is poured onto one sheet (803) and milled with a stainless steel rod to a uniform thickness and width, and the second sheet is placed on top. A roller is slowly rotated toward the nip, drawing the Teflon sheet and powder into the nip and creating a free-standing sheet between the Teflon sheets. The Teflon sheet (802) can be replaced with a Teflon-coated metal sheet of the same size, cut from a cookie sheet, for example. The electrode sheets (804) are removed using a safety razor or other sharp instrument and placed on clean paper. Each sheet is cut into a disk using an arch punch (e.g., a 3 / 4-inch (19 mm) diameter punch (e.g., McMaster Carr #3427A19)). The cathode sheet is placed on a current collector (e.g., gold-plated brass or nickel). A current collector may or may not be used on top of this first sheet, as desired. 10 mil nickel shim stock, flat nickel expanded metal, or no spacer (sheets directly contact each other) can be used. Following the protocol used for the current collector, a separator sheet is placed next, followed by the anode sheet. The current collector is placed on top of the anode. Here, gold-plated nickel or brass shim stock was used. The resulting energy harvester is assembled into a test fixture using a compressive force of, for example, 40 psi.

[0135] In another embodiment, the cathode has a diameter of 1 inch, the separator has a diameter of 7 / 8 inch, and the anode has a diameter of 3 / 4 inch. In this embodiment, short circuits between the electrodes are reduced or eliminated. In another embodiment, these diameters can be the same.

[0136] The separator layer may be omitted and the anode and cathode may simply be in direct contact with each other. Alternatively, the anode and cathode may have a concentration gradient of material, for example, resulting in a higher impedance near the interface between the electrodes.

[0137] In some embodiments, the anode and cathode electrodes are doped with carbon (graphite or carbon black), and the SSE layer between the anode and cathode electrodes is free of additives. In this embodiment, charge separation is achieved by utilizing the high impedance of the SSE layer. In yet another embodiment, no load exists that is lower than the total output impedance of the complete unit.

[0138] In many energy harvesters, the cells are placed within a plastic enclosure. Typical plastic enclosures are made of polyacrylate and polycarbonate, but any non-conductive plastic can be used. Adhesives include "airplane glue" for polycarbonate and methyl ethyl ketone (MEK) for polyacrylate. In one embodiment, the functional cells are enclosed in a chamber with a gas inlet and outlet, providing better control of the gas reactants and increased robustness of the resulting cell. When an enclosure is used, gas is pumped between the electrodes at a rate of 5-300 ml / min depending on the test, with an example rate including 50 ml / min per cell.

[0139] Example 3: Testing The test fixture holds the energy harvester with 125 pounds of force to the anode and cathode current collectors, which are made of gold-plated, nickel-200, or brass and mounted on cast acrylic supports. Testing was performed using a Solartron S1287 electrochemical interface and a Solartron S1250 frequency response analyzer, although many other test fixtures will work as well. The pellets were tested both individually and as energy harvesters sandwiched between gold electrodes. The entire device was placed in a plastic bag for gas environment experiments. Tests can typically be performed in air (20% oxygen), 100% oxygen, or argon (0% oxygen). When testing the assembled energy harvester, the cathode is used as the working and reference electrode. The anode is used as the counter and reference electrode. In this example, a negative current is expected upon short-circuiting or potentiostatic discharge of the energy harvester.

[0140] The energy harvesting cell is placed in an airtight enclosure, where gas is introduced into the cell through a port at one end of the enclosure and expelled through an exhaust port. Testing is typically performed in air (20% oxygen), 100% oxygen, or argon (0% oxygen) environments.

[0141] The test includes the following sets: Open circuit voltage (OCV) measurement for 1 minute AC impedance spectroscopy from 1 MHz to 1 mHz with 10 data points per decade. The units are normalized to physical terms by measuring the thickness of the compressed electrode or pellet and knowing the surface area. Polarization curve from OCV +0.25 to 0 volts at a scan rate of 1 mV / s. This gives the exchange potential (Eo), limiting current density, and power density. Voltage cycling voltammogram from OCV to +1.0 volts to -1.0 volts at 50 mV / sec for 5 cycles. The data obtained are as follows: R functionalis found by taking the maximum current at +1V and the minimum current at -1.0V, and by Ohm's law (R functional = dV / di) and calculate the slope between these two points as resistance. Hysteresis at 0 Volts: As with electrochemical or capacitive systems, when electrons are consumed and released during cycling, there is a spread in the current when the potential is going up compared to when it is going down. In effect, electrons are consumed or released, as opposed to simply passing through the system (as they would through a resistor). The greater this hysteresis, the better the crystal is at storing or releasing energy. The spread in current density in the positive and negative directions is the hysteresis, which can be measured as the voltage at zero current.

[0142] Example 4 CeO2, Ti4O7 anode, WO 2.9 Equal amounts of Co3O4 were used in all three electrodes: separator and cathode. CeO2 was mixed with 10% Teflon 7c (DuPont). Each pellet contained 2 grams of active material and pure nickel expanded metal (Dexmet) on both sides. The pellets were prepared as described above and stored in a 100% relative humidity environment for 4 days, resulting in a moisture content of 3.7% for the anode, 1.6% for the separator, and 0.5% for the cathode. To assemble the energy harvester, the anode pellet was bonded to a heavy gold-plated silver bezel with 5-minute curing epoxy around its periphery, while applying 40 PSI pressure to ensure good contact with the gold. The separator was then sealed with epoxy around its periphery, ensuring all oxygen transport from the cathode through the separator.

[0143] The pellet-type energy harvester described in Figure 7A above was subjected to eight cycles in an oxygen atmosphere, followed by a one-hour full short circuit and one-hour recovery period. Because the chamber was not sealed, oxygen diffused out and nitrogen diffused in, but very slowly. Figure 9 shows the current density at short circuit for multiple discharges. Note that in all discharge tests, the cathode is considered the working electrode, so the current is negative and the open-circuit voltage is positive, resulting in inverted vertical axes. The two highest traces (A) show oxygen introduction at approximately 700 seconds, while the other shows oxygen reintroduction at approximately 1600 seconds, demonstrating a dramatic improvement in performance. All other traces are in air (20% oxygen).

[0144] After each short circuit, the energy harvester was allowed to rest in oxygen for one hour. Figure 10 shows the recovery of the energy harvester. The energy harvester consistently recovered from a full short circuit, even after 25 hours of continuous short circuiting.

[0145] The energy harvester was then placed in various atmospheres. Figure 11 shows the results of this experiment. The energy harvester was started in air (20% oxygen). After about 5 minutes, the atmosphere was changed to pure oxygen, and the current density increased from about 30 mV to about 70 mV. After about 20 minutes, the atmosphere was switched to pure argon (0% oxygen), and the potential dropped to zero and even below that. After about 4 hours, the atmosphere was changed back to air (20% oxygen), and the potential returned to about 45 mV. This indicates that external gases have a significant effect on the performance of this energy harvester.

[0146] Next, complete short circuits were performed under various gas atmospheres, and Figure 12 shows the resulting bar graphs of current density under three different gas atmospheres. The current is a cathodic current, so it is a negative value and must be multiplied by -1 as shown in Figure 12. The strong influence of atmospheric air can be seen in the first bar, then oxygen (second bar), and finally argon (0% oxygen) (third bar).

[0147] Figure 13 shows that after leaving the device in air for 48 hours, the current was 170 μA / cm 2 Figure 1 shows a voltammogram of Energy Harvester 28716.4 (October 14, 2016, cell #4) showing a current density of 5 nW / cm at 0.066 volts and an exchange potential of nearly 100 mV. 2 This data is not impedance compensated.

[0148] Figure 14 shows that the AC impedance of this energy harvester is acceptably low. The pellet compression and current distribution of the nickel cross-bonded expanded metal help mitigate impedance issues. Figure 15 shows the Nyquist plot of this energy harvester, showing a large charge transfer resistance (Rct) of 18.8 kΩ.

[0149] Example 6: Exclusion of Water as a Liquid Electrolyte Water absorption improves functionality. To test whether water is a liquid electrolyte, an energy harvester was constructed by inserting five layers of dry nickel expanded metal between the electrodes shown in Figure 16, which shows an anode (7A1), five expanded metal disks (1601), a separator pellet (7A2), five more expanded metal disks (1601), and a cathode pellet (7A3). The source of the electrodes was the fully tested energy harvester described above. The anode and separator were then re-encapsulated under pressure with epoxy resin (7A5) to prevent external contact with air, leaving the cathode pellet (7A3) exposed to air. The energy harvester was reassembled and tested. In this example, electrons and gases can pass between the electrodes, but ions cannot. The pellets were prepared according to Example 1 above.

[0150] Figure 17 shows two voltammograms for these energy harvesters, 30616.1 (November 2, 2016, cell #1). The top line shows the performance with the electrodes close together, and the bottom line shows the performance with five expanded metal disks separating each electrode. The energy harvester performed well even without any ionic transfer between the electrodes. This indicates that ionic transfer is not required and that charge is transferred via electrons and possibly charged gas molecules, but not as ions.

[0151] Figures 18A and 18B are a series of graphs of short-circuit discharge and spontaneous charging of an OCV in air (20% oxygen). The discharge is shown in Figure 18A, with the top line showing the performance of the energy harvester with the electrodes in close contact, and the bottom line showing the performance with five layers of expanded metal between the electrodes. Clearly, there is no ion transport, only electrons and possibly charged gases, and performance continues.

[0152] Figure 18B shows the same set of voltage recovery curves after 1 hour of discharge. Again, the top row shows an energy harvester with the electrodes in contact, while the bottom row shows a battery with the electrodes physically separated and charged multiple times. This performance is also evident in the absence of ionic transport; the energy harvester transports charge solely via electrons.

[0153] These experiments demonstrate that charge can be transferred between electrodes using only electrons or charged gases by using electrodes that are isolated from each other but allow the electrons and gases to pass freely. Oxygen ionization occurs within each electrode (using water vapor as the reagent), and oxygen passes as a gas as electrons move from each cathode toward the anode.

[0154] The improved performance of assembling the electrodes closer together is a physical, not an electrochemical, advantage.

[0155] Without being bound by any particular theory, it is believed that the water present in the energy harvester does not act as an electrolyte, but rather as a reagent within the individual electrodes.

[0156] Example 7 Figure 19 shows a three-layer thin-film energy harvester (Experiment No. 36416) prepared as described above in Examples 2A and 2B using the rolling mill shown in Figure 8. Gold-plated 10 mil brass shimstock 1-inch diameter disks (7B1 and 7B2) were placed between each thin-film anode (7A1), separator (7A2), and cathode (7A3), sandwiched between a pair of gold-plated current collector (7B1 and 7B2) sheets.

[0157] Figure 20 shows the voltammograms for the separated-electrode energy harvester shown in Figure 19, as well as the curves for a three-layer thin-rolled electrode energy harvester, in which the electrodes were simply pressed on top of each other without spacers. The top trace had gold-plated brass spacers between the electrodes. The bottom trace was constructed by crimping the electrodes together without any spacers. Lower voltages indicated higher decades of current density. Both energy harvesters performed well, but the resulting parameters were different. Complete isolation of liquids, ions, and gases did not significantly decrease performance, indicating that this energy harvester transfers charge using only electrons.

[0158] Figure 21 shows the long-term OCV of the thin-electrode energy harvester with a solid spacer between the electrodes of cell 36516 (December 31, 2016). This energy harvester was exposed to oxygen at the start, reaching an OCV of 0.12 volts, which then dropped slightly, but maintained the voltage. After approximately 700 minutes, additional oxygen was added, and performance improved again. Note that the environmental "chamber" was simply a plastic bag closed at the top with a cable tie. It was by no means airtight, allowing atmospheric gases to diffuse over time. After approximately 825 minutes, the bag was filled with argon gas, and a sharp drop in performance was observed. After approximately 875 minutes, oxygen was reintroduced into the "chamber," and performance recovered again. These results demonstrate that the energy harvester functions even when the electrodes are sandwiched or separated by an impermeable layer of nickel. This suggests that the surface area of ​​the active ingredient can be increased by wrapping or coating it on a metal foil.

[0159] Example 8 Figure 22 shows a cross section of a three-layer energy harvester fabricated using the Teflon rolling mill method described in Example 2B above. In this case, each electrode has a different diameter: the bottom layer is a 1-inch (25.4 mm) diameter cathode (7A3), the separator is 7 / 8-inch (22.2 mm) diameter (7A2), and the anode is 3 / 4-inch (19 mm) diameter (7A1). Paper insulation is fabricated to prevent the current collectors from shorting the anode and separator 2201 to the current collecting disks (7B1 and 7B2). This prevents accidental shorting between the anode and cathode, or a direct short circuit of the energy harvester itself. This energy harvester has been subjected to various tests and has performed excellently in all tests to date.

[0160] Short-Circuit Testing: Figure 23 shows the current density for three 24-hour complete short-circuit tests (September 1, 2017) on cell 24417. The current density is much higher than in previous tests, which used progressively thinner electrodes to prevent accidental shorts between the electrodes. These lines indicate several conditions, including gas changes. Considering the lowest line, this represents the initial discharge. The energy harvester was dried after fabrication. For approximately 90% of the test, it was exposed to 100% relative humidity (RH), which significantly improved performance. The next line above that shows the same energy harvester being used continuously in air and at 100% RH until pure oxygen was introduced for 20% of the test. At approximately 25% of the test, pure argon was introduced, removing all oxygen from the test chamber. At 85% of the test, air was introduced (20% oxygen). The top line shows that after a short rest in 100% RH air, oxygen was introduced at the end of the 24-hour test, significantly increasing the current density output. The effect of atmospheric oxygen is clearly evident in the resulting open circuit voltages, with oxygen showing the highest values.

[0161] OCV Recovery Test: Figure 24 shows the OCV after each extended discharge from Figure 23. The bottom line shows the OCV recovery in argon (nearly no oxygen). Note that the test chamber is not completely sealed against atmospheric oxygen contamination. The middle line is the OCV recovery in air, and the top line is in 100% oxygen. Again, it is clear that atmospheric gases play a large role in performance.

[0162] Figure 25 summarizes the OCV across trials from the graph in Figure 24. The light grey bars indicate the rate of increase (i.e., the initial slope of recovery), and the dark bars indicate the voltage reached after 30 seconds.

[0163] The energy harvester was tested primarily with 24-hour dead short-circuit discharge cycles and varying rest periods. Figure 26 plots the dead short-circuit discharges over the life of this energy harvester (Run #24417) in chronological order. Most of the bars represent the current density after a 24-hour test in 100% relative humidity air. Gray bars #4 and #5 represent one-hour discharges in oxygen. The fifth-to-last graph (#20) represents a 12-day discharge in 100% relative humidity air. The fourth-to-last graph (#21) represents a continuous change in ambient gas. The longest discharge is the last bar (#24), showing the current density after five days of discharge. The current output increases over time. The energy harvester appears to self-charge while discharging. The total discharge time for this energy harvester in this series of tests was 560 hours (23 days), delivering 1.5 coulombs.

[0164] The final bar of this test was repeatedly interrupted to measure impedance values. Figure 27 shows this long-term discharge, which was conducted over several days with varying atmospheric gas compositions. The discharge was interrupted several times for several minutes to measure impedance values ​​(shown in Figure 29 below). This long-term test began in a dry state, followed by approximately 24 hours of gas testing in a 100% RH air environment. After 12 days, the next series of gas tests, as shown in Figure 27 below, were conducted. After approximately 290 hours (12 days), the chamber was filled with argon to displace the oxygen.

[0165] Figure 28 shows typical results when air was introduced initially, followed by oxygen after approximately 294.5 hours (12.25 days) as power output increased. The oxygen was then replaced with argon after approximately 294 hours. Air was then introduced 30 minutes later, and argon was introduced after approximately 300 hours. Argon was then introduced multiple times thereafter as atmospheric air continually diffused into the test chamber, again demonstrating the importance of oxygen in this energy harvester.

[0166] Regarding Figure 27, the chamber was refilled with 100% Rh air and operated for an additional 6 days. After the test, the cell not only fully recovered, but also exhibited a higher current density. This cell operated for approximately 20 days without degradation, and the current density improved over the test period.

[0167] Figure 29 shows the relationship between AC impedance and current density at 65 kHz as the energy harvester humidifies from a dry state to a saturated state. 2 values) is seen, which indicates a linear relationship. Without being bound by any particular theory, this would seem to suggest that the change in impedance with increasing current density is caused by water intrusion. In this example, the AC impedance decreases as the current density increases.

[0168] Example 10 A three-layer energy harvester was fabricated using the Teflon rolling method described above in Example 2B, "Rolled Electrodes." In this example, Teflon (PTFE) was added as a water suspension called Teflon 30. These particles are very small compared to the T7c powder described above.

[0169] The recipe for this 12 gram mixture is as follows:

[0170] [Table 3]

[0171] In this embodiment, 40 volume percent Teflon was added to each electrode, similar to that used in Teflon 7C.

[0172] The procedure is as follows: (1) Weigh out the active powder as usual, but without Teflon 7C (alternatively, Teflon F-104 can be used). (2) Place the powder in a 100cc beaker and add 50cc of distilled water. (3) Insert a stir bar and vortex vigorously to avoid drawing in air. (4) Add Teflon emulsion T30 dropwise. (5) Stir for about 30 minutes. (6) Prepare a Buckner funnel and filter the slurry under high vacuum. (7) Place the filter paper with the filter cake still attached in a glass dish. (8) Place in a 120°C drying oven until dry (about 6 hours for this 12 gram recipe). (9) Alternatively, place in a desiccator at room temperature until dry (approximately 24 hours). (10) Scrape the dried cake from the filter paper, add a small amount of water according to the recipe, and then grind it in a high-shear blender. (11) Form the electrodes using a rolling mill.

[0173] The resulting electrodes were more robust than those made using the dry method, and the energy harvesters were relatively easy to form.

[0174] Figure 30 shows the limiting current obtained from the initial voltammograms after fabricating several energy harvesters. The first bar shows the limiting current (LC) of the new energy harvester using dry Teflon 7C binder before humidification. The second bar shows the LC after humidification. The third bar shows the initial performance of the energy harvester fabricated using liquid emulsion T30 binder where the water had been removed by evaporation.

[0175] Without being bound by theory, Figure 31 shows a schematic of the charge flow in an exemplary energy harvester described herein. It is believed that oxygen enters the cathode 7A3 carrying two negative charges (electrons). The oxygen clings to the crystal structure and defects of the cathode material 3101 (e.g., Co3O4), creating excess electrons that slide onto the CeO2 crystals with loosely bound oxygen atoms, which carry the two electrons. These electrons are then transported to the WO 2.9The electrons are attracted to the low electronegativity of the CeO2 and move freely to separator layer 7A2, facilitated by CeO2 "electrolyte" 3102. The transition metal suboxide (e.g., TiO) in anode 7A1 has a higher electronegativity than the Co3O43 101 in cathode 7A3. These electrons are released by the reaction of oxygen with hydroxide ions, producing water vapor within anode body 3103 and emitting it into the environment. Current collector 7B1 accumulates the excess electrons, creating a potential across load 3104 and transferring the electrons back to cathode current collector 7B2.

[0176] Layer 7A2 is optionally not included.

[0177] Example 11 Low impedance, three-electrode design:

[0178] In this embodiment, the cell separates the charges using high-impedance sections. For example, the anode and cathode can comprise carbon (e.g., graphite or graphite) to reduce the impedance of the electrodes while simultaneously maintaining high impedance with a layer of SSE disposed between the electrodes as a solid separator (Figure 32). In another embodiment, Ti4O7 is added to the SSE to increase the DC resistance. This embodiment can increase power density by approximately 10-fold.

[0179] In the exemplary embodiment of FIG. 32, "A" is the anode, composed of active compound and carbon, "Sep" is the SSE, and "C" is the cathode and carbon. In another embodiment, the carbon content can be about 5%. In another embodiment, TiO or other impedance-increasing components can be added to the SSE separator layer to increase resistance. The carbon is preferably nano-sized acetylene carbon black powder. Carbon was tested in the form of carbon black using CABOT Vulcan XC72R (also known as "V72" for short) and alternatively, Asbury Graphite Mills "Nano307" powdered graphite. A content of less than 5% is optimal, but even 0.5% is effective. Mixtures of the two carbons were also tested.

[0180] To better understand the impedance characteristics of the exemplary cell, the DC resistance of each part was measured. Table 4 shows the DC resistance of the cell components. Components 1-4 are the source chemicals, components 5-6 are the anode with and without carbon, component 7 is the SSE, and components 8 and 9 are the cathode with and without carbon. Items 5-9 all also contain 40 volume percent unsintered Teflon powder.

[0181] [Table 4]

[0182] Figure 33 shows that this example 3-layer design achieves 12.5 times the discharge rate compared to the 34818 cell (December 14, 2018), which was the highest value achieved in previous testing without carbon in the electrodes. This cell was a 2-electrode design.

[0183] FIG. 34 shows the dead short circuit discharge of the cell with and without carbon in the electrodes with an eight-fold increase in current density.

[0184] Figure 35 shows the potentiostatic discharge of the cell, initially in humid air (20% oxygen), then switched to 100% humid oxygen after 4.5 hours. At 6 hours, the gas was switched to humid argon (0% oxygen), and at 12 hours, the gas was switched back to humid air. From this point on, it appears that the oxygen content influences the power output. Without being bound by theory, the fact that the argon atmosphere never goes to zero suggests that water vapor is being electrolyzed to generate oxygen in situ.

[0185] Figure 36 shows the power output curves for three example designs. The bottom curve is a two-electrode design with no carbon. The top two curves are three-electrode designs, one with 3% nanographite and one with 3% Vulcan 72 carbon black added to the anode and cathode, with an SSE layer between the two to separate the charge at a relatively high impedance.

[0186] Next, carbon black was used in the anode and cathode at the same loading as the graphite used in the previous experiment. After "activation" (short circuit for 24 hours, then OCV for 6 hours), the carbon black cell exhibited a slightly higher power density than the graphite cell, although the graphite had a slightly higher exchange potential. Alternatively, carbon black and graphite can be mixed in the electrodes.

[0187] In one embodiment, carbon can be added to the anode and cathode in an amount of about 2% to about 6%. In another embodiment, the amount of carbon added to the anode and cathode can be about 4%.

[0188] Example 12 These electrodes can be fabricated using a paint-on method if the binder is liquid-based and subsequently removed. A paint-on energy harvester was developed using a 25% dilution of latex media (Lot No. 03717). Each electrode was rolled and then reground to break down the fiberized Teflon fibers. The resulting mixture was mixed 50 / 50 with a 25% latex binder solution to create a thick, paint-on-a-metal material. This paint-on-a-metal material was applied to a 1-mil-thick nickel plate that had previously been thinly coated with a 50% diluted Timrex LB1016 graphite conductive paint. Each electrode was allowed to dry between applications. The final thickness was only 12 mils (0.012 inches, 0.3 mm). The electrodes were then punched into discs using a 3 / 4-inch arch punch. This energy harvester demonstrated feasibility, but the current density was lower than that of the rolled or pelleted methods.

[0189] Example 13 An example of a low impedance three-electrode design using gold-plated current collectors, nanopowder size, and carbon additives was tested.

[0190] In this embodiment, the cell separates the charge using high impedance sections, as described in Example 11. In this example, the anode current collector was a brass sheet current collector with thick gold plating, and the cathode was a porous carbon fiber (Sigracet25 BC obtained from FuelCellStore.com) cloth current collector. Without being bound by theory, it is believed that the carbon fiber cloth current collector allowed air flow to the cathode but not to the anode, resulting in the unexpected performance improvement.

[0191] In this example, the anode mixture is ground in a high-shear blender for about 5 minutes, and then the carbon is mixed in by hand, similar to "mixing" egg whites into cake batter, until the mixture is uniform in color (e.g., about 3 minutes). The same procedure applies to the cathode powder (e.g., the SSE is mixed in a high-shear blender, but no carbon is added).

[0192] FIG. 37 shows the performance improvement in three stages as polarization curves presented as voltammograms.

[0193] Scan c was generated from the cell that previously showed the best results. Scan b was generated from a cell that added carbon additives to the anode and cathode during high-shear milling, resulting in a 3.7-fold increase in current density compared to the lowest scan. Scan a was generated from a cell with 2% V72 carbon black added to the anode and cathode using the heterogeneous mixing method described above, resulting in a 38.4-fold increase in current density. All components in this cell were nanosized except for the carbon, and the cathode current collector was porous carbon paper with a thick gold-plated brass anode current collector. The carbon paper used in this and other embodiments may advantageously be Sigracet22BB, available, for example, from The Fuel Cell Store (fuelcellstore.com).

[0194] Example 14 FIG. 38 shows the performance improvement from the three-electrode design of Example 13, showing the first derivative of the polarization curve (ie, the power versus applied potential curve).

[0195] Scan c was generated from the cell that showed the best results to date. Scan b was generated from a cell that added carbon additives to the anode and cathode during high-shear milling, resulting in a 5.7-fold increase in power density compared to the lowest scan. Scan a was generated from a cell that added 2% V72 carbon black to the anode and cathode using the heterogeneous mixing method described above, resulting in a 110-fold increase in current density. All components in this cell were nanosized except for the carbon, and the cathode current collector was porous carbon paper with a thick gold-plated brass anode current collector.

[0196] Example 15 A series of water and glycerin mixtures were used to generate humidified air and a fully functional three-electrode cell was subjected to dead short-circuit discharge testing. Figure 39 shows the resulting power output (i.e., current density). At 85% relative humidity, the final performance is 50% of the maximum at 100% relative humidity. In some embodiments, increasing the relative humidity (e.g., above 50%) can increase the current density.

[0197] Example 16 In this example, cells were prepared using the active component TiO at the anode and CoO at the cathode. One of the cells was charged with protons (H + ), which transports only activated Nafion® (chemical formula CHF 13A sulfonated tetrafluoroethylene-based fluoropolymer copolymer of 05S·C2F4 (see DuPont Product Bulletin P-11 "Nafion® NR211 and NR212," www.nafion.com / en / - / media / files / nafion / nafion-nr211-nr212-p-11-product-info.pdf?rev=b3a97676150d4db5b4cd7518491a8f94) separator was used. Another cell was prepared using an AEM-215-30 anion exchange membrane (AEM) separator. This exemplary cell using the Nafion® separator showed a 13-fold higher current output with the Nafion® separator than with the AEM. Without being bound by theory, it is believed that charge transfer occurs via hydroxyl (OH) groups. - ), is believed to be responsible for proton transport from the anode to the cathode. In one embodiment, in the exemplary three-electrode design, higher current output can be achieved using a Nafion® separator.

[0198] Example 17 Figure 40 shows the specific power density of the active components. Figure 41 shows an example cell 411 using only the active components (Ti4O7 and Co3O4) and the active components and SSE separator (CeO2 and WO 2.9 ) mixed with the SSE separator. As shown in Figure 40, the specific power output is improved by approximately 20-70% by combining the exemplary active components with the SSE separator. In this example, cells can be made with only the active components (Ti4O7 and Co3O4), but the SSE (CeO2 and WO 2.9 ) results in a dramatic increase in performance (e.g., three times the power density and four times the specific power). Without being bound by theory, it is believed that the SSE in this example acts catalytically or functions in the active transport of oxygen molecules.

[0199] Example 18 Using the exemplary stacked electrode, cells were prepared with electrode thicknesses increased by two, three, and four times. In this example, the single-layer electrode thickness was 0.23 mm. The thickness series used was 0.23 mm, 0.46 mm, 0.69 mm, and 0.92 mm. As shown in Figure 41, performance improved by approximately 70% up to three layers (0.69 mm), and by approximately 50% at 0.92 mm. At 0.46 mm, an improvement of approximately 10% was observed. In this example, the power density performance of the cell was surprisingly improved with thicker electrodes, with the limit being 0.23 mm < 0.46 mm < 0.69 mm = 0.92 mm.

[0200] Example 19 Mode and Method of Assembly: In one embodiment, the energy harvester is assembled as follows.

[0201] A solid anode current collector, which must be made of a material that does not react with the active ingredients. This can be nickel, gold, gold-plated metal, or carbon, and must cover most or all of the anode surface.

[0202] b. An anode composed of a mixture of a solid electrolyte and a transition metal suboxide. The physical form of this layer is compressed and held together using a porous binder. It can also be applied as a paint using a liquid binder that dries after application.

[0203] c. A layer called the "separator" consisting only of a solid electrolyte and a binder. It can be the same thickness as the anode and cathode, thinner than the anode and cathode, or not present at all.

[0204] d. A cathode consisting of a solid electrolyte and a transition metal suboxide, which is less electronegative than the suboxide used in the anode.

[0205] e. A cathode current collector, which must be made of a material that does not react with the active components. This can be nickel, gold, gold-plated metal, or carbon, and must cover most or all of the cathode surface. This layer is preferably porous, such as porous carbon foam or perforated metal.

[0206] Example 20 Binder: In this example, the powders described herein are not sintered but are bound together using a binder. They are therefore "green" (unsintered). Binders that may work in this energy harvester include fibrillated Teflon (PTFE), latex, albumin, hydrogel, aerogel, or other organic or inorganic binders with low electrical conductivity. The material must be porous and have a very high internal impedance, i.e., higher than the active ingredient of the present invention. The binder can be started from a solvent and, upon drying, results in a high-impedance, highly porous binder.

[0207] Example 21: Grommet and Cellulose Separator Example applications: The energy harvester can be used in low power applications where there is a constant supply of ambient air. Preferably, this air is in flow, such as from a ventilation fan or a moving vehicle. When installed in a digital watch, the energy harvester case must have a porous structure to allow air to pass through. Examples include, among others:

[0208] a. Gas sensors, because they are sensitive to the gas composition in the atmosphere

[0209] b. Low-power devices such as electronic clocks and low-power LEDs;

[0210] c. Places with constant air movement, such as in moving vehicles, in the flow of cooling or ventilation fans, over wind turbine blades, over aircraft wings and many others.

[0211] d. The anode portion can be painted onto a solid surface, with subsequent layers painted on top, and terminated with a porous current collector, providing high surface area and high current output for many applications.

[0212] Additional energy harvesters according to embodiments of the present invention may also be used to implement the exemplary applications listed above in Example 21. Examples of such additional energy harvesters are described below.

[0213] Additional energy harvesters may retain many of the features of previously described energy harvesters, such as Example 2A, including (1) the powder mixing method (high shear for all but the carbon, which was mixed by hand), (2) all components being nanosized, (3) the use of a powder chute to slightly pre-compress the powder before rolling the electrodes, and (4) the cell being tested at 125 lbs of force.

[0214] Further energy harvesters may include variations / modifications from the previously described energy harvesters, including, but not limited to, (1) new formulations that do not contain CeO2, (2) new assembly methods that use electrode grommets and a pre-compression step, (3) new separators that do not use SSEs but instead use separators made of cellulosic materials, which can be cellulose (optionally hydrated and unplasticized), cellophane, rayon, or other cellulose- or viscose-derived materials, (4) new cell bodies in which all or substantially all air ingress is through the surface of the cathode and the anode is largely sealed from gas transfer, and (5) the cathode current collector (transfer layer) is a fine stainless steel screen rather than the previously used tailed gold-plated brass disk.

[0215] One embodiment of such an energy harvester is shown in FIG. 42 and has the following configuration:

[0216] Figure 42 shows the five-layer design of the cell. The cell contains an anode pellet 4201 and a cathode pellet 4202. Both the anode and cathode are encased in a plastic grommet 4203, as shown in Figure 43. Polypropylene is a suitable material for the grommet, but nylon and other plastics that are stable in humid environments are also suitable. A cellophane sheet 4204 separates the two electrodes. Advantageously, this is unplasticized cellophane, but plasticizers that promote moisture transfer are also very effective. Most cellophane plasticizers are used to increase the sheet's strength and make it waterproof, but this is not a feature of this cell construction. We tested both silver-filled and unfilled cellophane, and both worked well. The cellophane was cut and soaked in distilled water for several hours. It was then removed from the water, lightly blotted between two dry paper towels, and placed between the grommeted electrodes. The anode current collector is then made from gold-plated brass 4205. The cathode has a layer of porous carbon paper (e.g., Sigracet22BB) 4206. On top of this is a very fine mesh stainless steel screen cathode current collector (TIMESETL304 stainless steel woven wire 200 mesh) 4207. All moist air enters the cell via the open grid pattern 4208 in the cell body. As with previous designs, the cell body (not shown) is made from polypropylene, although any moisture-resistant material could be used.

[0217] In this example, it looks like this:

[0218] Anode: 83% nTi4O7 + 17% nWO 2.9 It is composed of: 2.9 The ratio can be a little higher, but not much higher. This is bound with 40 volume percent Dalkin F104 Teflon binder (powder) and 2% nano-sized acetylene carbon black powder, preferably Vulcan XC 72R or Nao307.

[0219] Separator: The separator can be, for example, one of hydrous unplasticized cellophane and a proton exchange membrane. The cellophane may or may not be silver loaded.

[0220] Cathode: The cathode is 70% nWO 2.9 +30% Co3O4 (also known as W20O58). Alternatively, 72% nWO 2.9 The cathode may be composed of 28% Co3O4 (also known as W20O58). The cathode is bound with 40 volume percent Dalkin F104 Teflon binder (powder), which is then bound with 2% nano-sized acetylene carbon black powder, preferably Vulcan XC 72R or Nao307.

[0221] Generally, the cell assembly may comprise the following layers:

[0222] (1) Cathode current collector, which can be made of Siguracet 22BB carbon paper in the shape of a disk with a diameter of 27 mm and a thickness of 0.2 mm.

[0223] (2) Cathode disc and grommet assembly.

[0224] (3) Hydrated cellulose discs.

[0225] (4) Anode disc and grommet assembly.

[0226] (5) 27mm diameter gold-plated brass disc.

[0227] The cell may be constructed by a method according to an aspect of the present invention.

[0228] Weigh the electrode powder for the anode or cathode into a 250 ml plastic beaker. Next, add Daikin F104 Teflon powder. Mix the powder in a high-shear grinder at approximately 20,000 rpm for at least 1 minute, preferably about 2 minutes. A Krups® F203 coffee grinder is suitable for this purpose. Let the mixed powder sit for a few minutes to allow the dust to settle. Weigh the mixed powder and calculate the carbon content. Next, add the nano-sized acetylene carbon black powder and mix by hand with a flat spatula for at least 2 minutes, preferably about 3 minutes.

[0229] The resulting powder is pre-compressed in a paper-lined compression chute. First, a strip of paper is placed on the chute and the powder is spread onto the paper strip to a depth of approximately 3.5 mm. A wide plastic spatula is used to level the powder with the knife-like edge at a 45° angle to the powder. This leveling is done in a back-and-forth motion until the powder is very evenly distributed and lightly compressed onto the rails of the chute to a depth of approximately 2.0 mm (or 2.5 mm). A second piece of paper is placed on top.

[0230] The arrangement is then compressed, for example, using a rolling mill between two Teflon-coated steel plates at a compressive force of approximately 2,000 pounds. Using, for example, a spatula, the powder and paper arrangement is lifted and placed on the first steel plate, which is then placed on the entry platform of the rolling mill. The rolling mill is set to 25 psi, and two 4-inch pancake cylinders exert a force of just over 1,000 pounds at that pressure. A second steel plate is placed on top of the arrangement and rolled within the rolling mill. The arrangement is then placed on a clean worksheet, and the two paper strips are removed.

[0231] The result is an electrode strip approximately 180 mm long and 0.09 mm thick. From this electrode, electrode disks are blanked using an arch punch or equivalent.

[0232] The electrode grommet was 3D printed using PETG filament. Figure 43 shows a cross section of the part. The ID (inner diameter) of the grommet is 25mm and the OD (outer diameter) of the disk is 22.25mm. When compressed between parallel plates with a force of 2000 lbs, the OD of the electrode expands and compresses within the grommet, simultaneously reducing the thickness of the part. The result is a strong, uniform part that is easy to assemble. The OD of the assembled part is 28mm.

[0233] This is done for both the anode and cathode electrodes.

[0234] The cellulose separator is blanked at 27 mm so that it completely covers the active electrode and is easily placed over the electrode grommet assembly.

[0235] Place the blank cellulose sheets on a water-soaked paper towel. Place a second paper towel on top and leave for at least 16 hours. The paper towel cover is used to keep the sheets submerged in distilled water.

[0236] When using the cellulose, remove it from the dish and place it on a dry paper towel, wiping it briefly to remove any remaining water.

[0237] The cell can then be subjected to testing.

[0238] The tester supplies all of the humidified air from the cathode side of the cell, which has no obvious outlet, but the cell is not sealed. This holder is shown in a 3D CAD image in Figure 44. The inlet gas is from the bottom, facing the cathode. The holder is also shown in cross section in Figure 45, showing the honeycomb-patterned airflow manifold interconnections. The cathode current contact, not shown, is a very fine stainless steel screen disk with a protruding electrical contact tail. The anode current contact, also not shown, is a gold-plated brass disk with a protruding electrical contact tail.

[0239] The cell assembly, comprising the first through fifth layers, is placed in a cell test specimen, which allows all air flow from the cathode side of the cell and restricts gas ingress or egress to the anode.

[0240] The chemical mechanism described below suggests that oxygen is utilized at the cathode but not at the anode. Oxygen gas is released from the anode, but at a very low rate, making it highly unlikely that the gas will become trapped.

[0241] The assembled cell is placed in a test fixture that applies a force of approximately 125 lb. If the cell were assembled into individual components, such testing would not be necessary.

[0242] Without being bound by any particular theory, the following mechanism 3 may be relevant: This explanation accounts for the current understanding of chemical mechanisms and environments.

[0243] (Mechanism 3) In the following description, bold symbols indicate either the environment (H2O vapor) or the external circuit (e - ) and the symbols in italics indicate that the water is dissolved or mobile within the cell (H2O v , H2O, H + The underlined symbols represent the state of efflux from the cell (O2 from the anode, e from the anode). - , H2 from the cathode).

[0244] Anode (TiO x and WO 2.9 ): [ka]

[0245] Or, to simplify, [ka]

[0246] TiOx catalyzes the dissociation of water molecules. Using the vacancies ("V") shown in the figure, we propose the following: [ka]

[0247] WO 2.9 mechanism [ka]

[0248] The second reaction is reversible.

[0249] The anode expels O2 and gives off electrons, but does not take in oxygen.

[0250] Separator The proton exchange membrane Nafion 211 works as well as non-plasticized "battery grade" cellophane for the following reasons: · The transfer of protons (in the case of Nafion®) and all ions in the case of cellulose is easy. There is no electron loss through the SSE layer. All electrons must pass through the load.

[0251] Cathode (Co3O4 and WO 2.9 ):

[0252] WO 2.9 This is the reverse of the anodic reaction and requires oxygen from the air and electrons from an external circuit. [ka]

[0253] Or, to simplify, [ka]

[0254] Oxygen is evolved from air in a reversible reaction. Co3O4 set (which does not require external oxygen and + and 2e - (Only necessary) [ka]

[0255] Or, to simplify, [ka]

[0256] Mechanism of water splitting catalysis by Co3O4: [ka]

[0257] Or, expanded:

[0258] Co3O4 is cobalt with a valence of +4 and cobalt +3 with four resident oxygens and one vacancy (or two). [ka]

[0259] The cathode expels H2, accepts electrons, and inhales O2.

[0260] This explains why it works best with oxygen and air is good - argon (i.e. no oxygen) will also improve performance, but not by much.

[0261] Figure 45 shows what enters, leaves, and passes through the cell. {This figure will be placed in the final specification drawing, with the color coding changed to highlighting.} [ka]

[0262] Ingress into the cell: The cathode is filled with water vapor (HO v ) and oxygen (O2). The cathode receives electrons (e - )

[0263] Internal charge transfer refers to the transfer of protons (H + ) is transported through liquid water (H2O) on the surface. The driving force is due to both Knudsen diffusion and the concentration gradient. v ) also moves freely within the porous body of the electrode.

[0264] Emissions from the cell: Oxygen (O2) from the anode and hydrogen (H2) from the cathode are emitted in gaseous form. Electrons (e - ) leaves the anode, performs some loaded work, and returns to the cathode.

[0265] Unless otherwise stated, the electric potentials (Eo) reported here are from the following source: en.wikipedia.org / wiki / Standard_electrode_potential_(data_page)

[0266] The term "energy harvester" as used herein is not limited to an enclosed body with electrodes in the mechanical sense, and one or more sides of the device may be open to the environment. The term "solid-state energy harvester" may be interpreted as a "solid-state energy source."

[0267] The device may function as an energy storage unit, such as a battery, or as a capacitor.

[0268] Example 22 This example demonstrates an aspect of the present invention that can generate electricity using water vapor without the need for exposure to air. Applications of this embodiment include, but are not limited to, subcutaneous applications such as deep brain stimulators, intraocular pressure monitors, artificial urinary sphincters, and bone fusion applications. These applications provide an environment with a constant temperature (e.g., 37°C) and 100% RH, but no oxygen. Therefore, we developed a new cell housing that blocks all atmospheric oxygen, demonstrating that the present invention can operate in an oxygen-free environment.

[0269] (material) Porous Teflon tape: Saint Gobain DoM30 / 23 / 00 / Natural or equivalent.

[0270] High-quality nickel cloth: TIMESETL304 stainless steel woven wire 200 mesh (see amazon.com / gp / product / B081QB3BLF / ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1) or equivalent.

[0271] Closed-cell porous neoprene compressible gasket material: Neoprene soft gasket material, McMaster Carr #93375K402 or equivalent.

[0272] Conductive paint: MTN Water-Based 300 Spray Paint - WRV9011 - Carbon Black

[0273] In this example, the cell is assembled in a similar manner to the other examples, with the main difference being that the cell is sealed from the atmosphere. Anode: 77% n Ti4O7 + 23% n WO 2.9 +40v / v Teflon binder was mixed in a high shear grinder, and 2% n carbon black (V72) was also mixed. The cathode is 70% WO 2.9, 30% Co3O4 (also known as W20O58), and 40 v / v Teflon binder were mixed together in a high shear grinder, followed by 2% carbon black (V72). More specifically, the powders were mixed in a blender at 20,000 rpm for 2 minutes, and then carbon black (V72) was mixed in for approximately 3 minutes. The powder is spread onto a paper-lined compression chute to a depth of approximately 3.5 mm, smoothed and pre-compressed to a depth of approximately 2 mm, and then compressed between two Teflon-coated steel plates in a rolling mill at a compression force of approximately 2000 lbs. The result is electrode strips approximately 180 mm long and 0.09 mm thick. Electrode discs are punched from this strip using an arch punch or equivalent machine. The discs have an outer diameter (OD) of 22mm. They are inserted into a polypropylene gasket with an inner diameter (ID) of 23mm and an OD of 28mm (see Figure 42). They are then compressed in a vertical hydraulic press with a force of 2000 lbs, which compresses the lip downward and expands the OD of the electrode to the ID of the grommet. This procedure is performed on both the anode and cathode electrodes. Punch out 22mm discs from a 0.02mm thick cellulose sheet and place them on a water-soaked paper towel. Place a second paper towel on top and leave for at least 16 hours. The paper towel cover ensures that the sheet remains submerged in distilled water. When ready to use, remove the cellulose from the dish with tweezers, place it on a dry paper towel, and pat it briefly to remove any remaining water.

[0274] (cell assembly) The electrode grommet was 3D printed using PETG filament. Figure 43 shows a partial cross section. The grommet ID is 25mm and the disk OD is 22.25mm. These were compressed between parallel plates with 2000 lbs of force, which caused the electrode OD to expand and compress into the grommet while simultaneously reducing the thickness of the grommet itself. The result is a strong, uniform part that is easy to assemble. The assembled part has an OD of 28mm.

[0275] The cellulose separator is blanked at 27 mm so that it completely covers the active electrode and can be easily placed over the electrode grommet assembly.

[0276] All housing components are 3D printed using PETG filament, but any water-resistant filament will do.

[0277] Figure 47 shows an exploded view of an oxygen-free cell. 470 indicates the chamber that holds the degassed water. This is covered by one or two layers of porous Teflon 471 film, the type used for the air electrode in metal-air batteries. This is a full-diameter disk that allows the cell to be exposed to 100% RH while preventing liquid water from reaching the cell. Item 472 indicates the fine nickel cloth cathode current collector. Item 473 is a soft, closed-pore neoprene gasket to prevent atmospheric oxygen from reaching the cell. Item 474 indicates the cell, which, as above, is three-layered, in this illustration with the cathode assembly on the bottom, then the hydrated cellulose separator, and the anode assembly on top. Item 475 is the anode current collector. This is preferably a non-reactive metal such as gold-plated brass, nickel, or other metal. Item 476 is the anode cover, which is a simple disk with a small recess (not shown) to accommodate the anode current collector.

[0278] Figure 48 shows a semi-compressed view of an oxygen-free cell. 480 denotes the chamber that holds the degassed water. This chamber is covered by one or two layers of porous Teflon 481 film, the type used for the air electrode in metal-air batteries. This film is a full-diameter disk, preventing liquid water from reaching the cell while allowing the cell to be exposed to 100% RH. 482 denotes a fine-grained nickel cloth cathode current collector. 483 denotes a soft, closed-pore neoprene gasket that prevents atmospheric oxygen from entering the cell. 484 denotes the cell body, which, as noted above, is three-layered: in this view, the cathode assembly on the bottom, followed by a hydrated cellulose separator, and the anode assembly on top. 485 denotes the anode current collector. This is electrically conductive, preferably made of gold-plated brass, nickel, or some other metal-insensitive material. 486 denotes the anode cover, a simple disk with a small recess (not shown) to accommodate the anode current collector.

[0279] Preferably, to reduce internal resistance, the outer surface of the electrode is coated with a conductive paint. While a water-based spray paint was used in this example, a 50% diluted version of the paint used to coat the inside of alkaline batteries would also be effective. This improved the internal impedance and current output.

[0280] Teflon binders are hydrophobic, but other hydrophobic binders can also be used. Many hydrophobic additives are used in the battery industry, including PVDF (polyvinylidene fluoride), Targray's modified SBR (styrene butadiene copolymer), FEP (fluoropolymer powder), paraffin, epoxy resin, and similar materials.

[0281] An energy harvester is described herein as a device that collects energy from the environment rather than storing it. Although in this embodiment the cavity containing the electrodes is sealed off from the surrounding environment during operation of the device, this embodiment is still referred to herein as an energy harvester.

[0282] While this embodiment uses a cellulosic separator that meets the requirements of hydrophilicity and wettability, separators other than SSE or separators containing metal oxides may also be used, including, but not limited to, polyolefins such as Setela and Celgard, fiberglass separators, separators containing polyester and nylon, and the like.

[0283] Mechanism: It is surprising that the cell of this example operates without atmospheric oxygen, considering the mechanism described above. Without being bound by any particular theory, the power generation mechanism in this embodiment is thought to proceed as follows.

[0284] (Cathode mechanism) The cathode is a proton (H + ), electron (e - ) and oxygen (O2) to produce H2O and H2.

[0285] WO 2.9 mechanism

[0286] (W +6 -V o -W +6 )+H2O v ←→(W +5 -OW +5 )+2H + ←→(W +5 -V o -W +5 ) = 1 / 2O2+2H + +2e -

[0287] (W +6 -V o -W +6 )+H2O v ←→(W +5 -OW +5 )+2H + ←→(W +5 -V o -W +5)1 / 2O2+2H + +(2e - +2H + )→

[0288] (W +5 -V o -W +5 )+1 / 2O2+2H + +2e - ←→(W +6 -OW +6 ) = +2H + ←→(W +6 -V o -W +6 )+H2O

[0289] Or, abbreviated:

[0290] 1 / 2O2+2H + +2e - ← WOx →H2O Here, 1 / 2O2 is produced from water vapor catalyzed by tungsten suboxide.

[0291] Mechanism of Co3O4: (No external oxygen required, H + and e - (only required)

[0292] 2Co3O4+2H + +2e - →2Co3O4+H2

[0293] Or, abbreviated:

[0294] 2H + +2e -CoOx →H2

[0295] Mechanism of Co3O4 catalyst in water recombination:

[0296] Co3O4V+H2O+2H + +2e - →Co3O4O + 1 / 2H2+3H +

[0297] Co3O4O+1 / 2H2+3H + →Co3O4V+H2O+H2

[0298] Or, expanded:

[0299] Co3O4 is a compound consisting of cobalt with a valence of +4 and four resident oxygen atoms (Co +4 Co +3 O4) and cobalt+3 with one vacancy (or two).

[0300] (Co +3 -V o -Co +3 ) + H2O → (Co +4 -O-Co +4 )+2H + + 2e -

[0301] Co3O4 and WO in the conduction band 2.9 Electron transfer

[0302] 2(W +5 -V o -W +5 )+2(Co +4 -V o -Co +4 )+4e - →2(W +6 -V o -W +6 )+2(Co +3 -V o -Co +3 )

[0303] (W +6 -V o -W +6 )+H2O→(W +5 -OW +5 )+H2

[0304] (Co +3 -V o -Co +3 ) + H2O → (Co +4 -O-Co +4 )+H2

[0305] (Anode mechanism:) The anode is TiO x and WO x as a catalyst to split water, consuming H2O and producing protons (H + ), electron (e - ), and releases O2.

[0306] Tungsten Set

[0307] (W +6 -V o -W +6 )+H2O→(W +5 -OW +5 )+2H +

[0308] (W +5 -OW +5 ) → (W +5 -V o -W +5 )+1 / 2O2+2e -

[0309] Or to simplify: H2O← WOx →1 / 2O2+2H + +2e -

[0310] Titanium Set

[0311] Generally: H2O + TiO x →TiO x OH - +H + →TiO x +1 / 2O2+H + +2e -

[0312] In detail: [ka] [ka]

[0313] Or, simply: H2O- TiOx →1 / 2O2+2H + +2e -

[0314] Or combined:

[0315] H2O- TiOx&WOx →1 / 2O2+2H + +2e -

[0316] Electron transfer between WO3 and TiO2 in the conduction band:

[0317] 2(W +5 -V o -W +5 )+2(Ti +4 -V o -Ti +4 )+4e - →2(W +6 -V o -W +6 )+2(Ti +3 -V o -Ti +3 )

[0318] The definition of Kroger-Vink notation used here can be found in many sources, including academic sites such as Wikipedia (en.wikipedia.org / wiki / Kroeger-Vink_notation) or (www.tf.uni-kiel.de / matwis / amat / def_en / kap_2 / backbone / r2_4_2.html).

[0319] All references cited in this disclosure are incorporated herein by reference in their entirety.

[0320] While the present invention has been disclosed with reference to particular embodiments, numerous modifications, substitutions, and variations are possible to the described embodiments without departing from the scope and spirit of the invention as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but rather have the full scope defined by the claims and their equivalents.

Claims

1. 1. A solid-state energy harvester, comprising: (a) an anode comprising a first transition metal suboxide; (b) a cathode comprising a second transition metal suboxide; (c) a separator disposed between the anode and the cathode; at least one of the anode, the cathode, or the separator comprises water; the harvester generates electricity when electrically connected to an external load; Solid-state energy harvester.

2. The solid-state energy harvester of claim 1 , wherein the first transition metal suboxide and the second transition metal suboxide are the same.

3. The solid-state energy harvester of claim 1 , wherein the first transition metal suboxide and the second transition metal suboxide are different.

4. 4. The solid-state energy harvester of claim 1, wherein the anode further comprises a transition metal suboxide different from the first transition metal suboxide.

5. 5. The solid-state energy harvester of claim 1, wherein the cathode further comprises a transition metal suboxide different from the second transition metal suboxide.

6. 6. The solid-state energy harvester of claim 1, wherein the separator is hydrophilic.

7. 7. The solid-state energy harvester of claim 1, wherein the separator is substantially free of metal oxides.

8. 8. The solid-state energy harvester of claim 1, wherein the separator conducts protons and is electrically resistive.

9. 9. The solid-state energy harvester of claim 1, wherein the separator comprises water.

10. 10. The solid-state energy harvester of claim 1, wherein the anode further comprises a conductive additive.

11. 11. The solid-state energy harvester of claim 1, wherein the cathode further comprises a conductive additive.

12. 12. The solid-state energy harvester of claim 1, wherein the anode further comprises a hydrophobic additive.

13. 13. The solid-state energy harvester of claim 1, wherein the cathode further comprises a hydrophobic binder.

14. 14. A solid-state energy harvester as described in any one of claims 1 to 13, wherein at least one of the transition metal suboxides comprises tungsten.

15. 15. The solid-state energy harvester of claim 1, wherein at least one of the transition metal suboxides comprises titanium.

16. 16. The solid-state energy harvester of claim 1, wherein at least one of the transition metal suboxides comprises cobalt.

17. 17. The solid-state energy harvester of claim 1, wherein the anode and the cathode are both planar.

18. 18. A solid-state energy harvester according to any one of claims 1 to 17, wherein the anode and cathode are positioned parallel to each other.

19. 19. A solid-state energy harvester as claimed in any one of claims 1 to 18, further comprising a housing having a cavity therein, the anode and cathode being located within the cavity.

20. 20. The solid-state energy harvester of claim 19, wherein the housing seals off the atmosphere from the cavity.

21. 20. The solid-state energy harvester of claim 19, wherein the housing allows atmospheric air to reach the cathode.

22. 19. The solid-state energy harvester of claim 1, further comprising a plurality of anode and cathode electrode pairs, each of which generates electricity, all of the electrodes of the electrode pairs housed within the cavity.

23. 16. A solid-state energy harvester system comprising a first energy harvester and a second energy harvester, wherein the first energy harvester and the second energy harvester comprise solid-state energy harvesters according to any one of claims 1 to 15, and the first energy harvester is electrically connected to the second energy harvester.

24. 24. The solid-state energy harvester system of claim 23, further comprising a battery, wherein the first energy harvester and the second energy harvester generate electrons that are stored in the battery.

25. 1. A method of configuring a solid-state energy harvester to generate electricity, comprising: (a) preparing an anode mix comprising a first transition metal suboxide and a binder; (b) preparing a cathode mix comprising a second transition metal suboxide and a binder; (c) forming the anode mix in a first layer and the cathode mix in a second layer; (d) placing the first layer and the second layer on opposite sides of a separator; (e) electrically connecting the first layer to the second layer via an external electrical connection while the first and second layers are exposed to moisture; The solid-state energy harvester generates electricity. A method for configuring a solid-state energy harvester to generate electricity.

26. 26. The method of claim 25, wherein in the step (a) of preparing the anode mix, the anode mix further includes a first metal suboxide different from the first transition metal suboxide.

27. 27. The method of claim 26, wherein in step (b) of preparing the cathode mixture, the cathode mixture further includes a second metal suboxide different from the second transition metal suboxide.

28. 26. The method of claim 25, wherein in both said preparing steps (a) and (b), a conductive additive is added to both said anode mix and said cathode mix.

29. 26. The method of claim 25, wherein in both said preparing steps (a) and (b), a hydrophobic additive is added to both said anode mix and said cathode mix.

30. 26. The method of claim 25, further comprising wetting the separator with water.

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