METAL-TRITIUM NUCLEAR BATTERIES

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This patent application hereby claims priority from the United

States provisional patent application of the same title, which was filed on August 29, 2005, and assigned United States provisional patent application serial number 60/712, 1 12, teachings of which are incorporated herein by- reference.

FIELD OF THE INVENTION [0002] The invention generally relates to batteries and more particularly relates to nuclear batteries having a tritium loaded thin film disposed on one electrode, to provide a longer battery life. BACKGROUND OF THE INVENTION

[0003] A need exists for low cost, long-lived batteries for a variety of electronic devices, particularly but not limited to, in military, space, and commercial applications. The military especially desires such miniaturized batteries that can be incorporated into microchips, thus greatly reducing device volumes, because current batteries require orders of magnitude more space than the microchips themselves. There are many logistical and environmental costs associated with the batteries on the market today. [0004] A long-lived battery would dramatically reduce the costs involved with storing, replacing and disposing of batteries. The need for such long- lived batteries in space satellites and for space exploration missions is long- felt. The design and performance of commercial applications, including but

not limited to, flashlights; portable electronics, including but not limited to laptop computers, cell phones, personal digital assistants, and digital cameras/ camcorders; and medical computer-controlled devices, including but not limited to prosthetics, heart pacemakers, and defibrillators, would all be greatly improved, by such a battery. Additionally, long-lived batteries that could outlive the design life of the electronics in various devices would revolutionize the battery industry and eliminate the pollution problem caused by exhausted batteries. [0005] Attempts have been made to use the energy inherent in the decay of radioactive materials as the basis for a long-lived battery. Several different approaches have been taken to incorporate radioisotopes into batteries. Tritium, ³ H, has generally been used in these attempts. It is the heaviest isotope of hydrogen with an atomic mass of three because it has one proton and two neutrons in its nucleus. It is unstable and emits beta particles (electrons) and has a half-life of 12.3 years. While tritium has been generally, previously used, the present invention comprises a novel circuit configuration and methodology which permits a high concentration of tritium to be stored in a small area, overcoming a disadvantage of the prior art. [0006] It has been shown by LaI and Blanchard that the use of tritium in a battery can conservatively have an energy density of 850 milliwatt-hours per milligram (mWh/mg). This is 2,800 times the energy density found in the best commercial Lithium-ion batteries in use today. For comparison

purposes, lithium-ion in a chemical battery has an energy content of 0.3 mW-Hrs per mg. Methanol in a fuel cell has an energy content of 3 mW-Hrs per mg. Tritium in a nuclear battery can have an energy content of up to 850 mW-Hrs per mg. [0007] Further, LaI and Blanchard only disclose the use of tritium on micro-chips, while the present invention is directed towards not only microchips, but also bulk structures. The configuration used by LaI and Blanchard is also different than the present invention. Further, as explained above, the present invention provides a higher concentration of tritium in a smaller area through the use of metal hydrides.

[0008] The present invention provides a long-life nuclear battery which overcomes the disadvantages of the prior art as discussed below. SUMMARY OF THE INVENTION [0009] An object of the present invention is to provide a low cost, long life battery.

[0010] Another object of the present invention is to use tritium, ³ H, in a tritium loaded thin film disposed on one electrode of a nuclear capacitor. [0011] Still another object of the present invention is to provide a metal-tritium battery that can be scaled up from sizes that can be produced on a microchip to those at least as large as or larger than ordinary batteries, e.g., AA, C, and D.

[0012] Still another object of the present invention is to provide a nuclear battery which is based on tritium, with a half-life of 12.3 years.

[0013] Still another object of the present invention is to provide a nuclear battery that has a battery life that exceeds the design life of many- electronic devices.

[00014] Yet another object of the present invention is to provide a nuclear battery that eliminates the pollution problems caused by exhausted batteries.

[00015] Specifically, what is provided in one preferred embodiment is a battery comprising a capacitor having a first electrode and a second electrode. The first and second electrodes are parallel to each other and define a gap therebetween. A tritium loaded thin film is disposed on the first electrode and extends into the gap. The tritium loaded thin film further is electroplated onto a metal strip of the first electrode substrate. The tritium loaded thin film is comprised of a material selected from the group consisting of magnesium, lithium hydride, magnesium iron hydride, magnesium nickel hydride, sodium borohydride, lithium aluminum hydride and lithium borohydride. The thin tritium loaded film is separated from a second electrode by air or a thin insulating material. The invention further comprises a supercapacitor, capable of storing a charge moved from the capacitor, and additionally a clamping or Zener diode, in parallel with the capacitor and supercapacitor, whereby the clamping diode maintains a fixed voltage output. The battery life is a function of the thickness and area of an initial tritium volume disposed on the first electrode. Additionally, the battery is scalable.

[0016] In another embodiment, the present invention provides, a nuclear battery comprising a capacitor having a first electrode and second electrode, the first and second electrodes are parallel to each other and define a gap therebetween. A tritium loaded thin film is disposed on the first electrode and extends into the gap. A shorting metal electrode is connected to the first electrode. The shorting electrode is spatially adjustable relative to the first piezoelectric bimorph electrode, thereby varying the voltage to which the capacitor and piezoelectric bimorph can be charged. The invention further comprises a piezoelectric bimorph having a first and second bimorph electrodes. A magnet is attached to the second bimorph electrode, opposite from the shorting metal electrode. Additionally, a coil is located in proximity to the magnet and has a signal induced by the magnet, when the piezoelectric bimorph vibrates. A first power conditioning unit for low voltage, low impedance output is connected to the coil and a second power conditioning unit for high voltage, high impedance output is connected to the first bimorph electrode and the second bimorph electrode. The power conditioning units are rectifying units which permit a direct current output from an alternating current input. A charge is stored at the output of the power conditioning units on a second capacitor suitable for the desired voltage. The radioactive decay of tritium causes the capacitor to charge quickly to a high voltage, and then the voltage is applied to the piezoelectric bimorph causing it to bend to contact the shorting electrode, thereby shorting the capacitor and causing the piezoelectric bimorph to oscillate

rapidly, whereby the rapid oscillations of the bimorph cause a high voltage decaying signal to appear across the first and second bimorph electrodes. [0017] Further provided is a method of making a nuclear battery comprising the steps of providing a capacitor having a first electrode and second electrode, the first and second electrodes are parallel to each other [0018] and define a gap therebetween. A tritium loaded thin film is disposed on the first electrode and extends into the gap. A shorting metal electrode is connected to the first electrode. Additionally provided is a piezoelectric bimorph with a first and second bimorph electrode and a magnet attached to the piezoelectric bimorph, opposite from the shorting metal electrode. A coil is located in proximity to the magnet and has a signal induced by the magnet. A first power conditioning unit for low voltage, low impedance output is connected to the coil and a second power conditioning unit for high voltage, high impedance output is connected to the first bimorph electrode and the second bimorph electrode. The method further comprises the steps of radioactively decaying the tritium, causing the capacitor to charge quickly to a high voltage thereby providing extended battery life. The shorting metal electrode is spatially adjustable to vary the distance between the shorting metal electrode and said first bimorph electrode to thereby vary the voltage to which the capacitor and piezoelectric bimorph can be charged.

[0019] The present invention also discloses a method of using a nuclear battery comprising the steps of radioactively decaying tritium causing a

capacitor to charge quickly to a high voltage thereby providing extended battery life, applying a voltage to a piezoelectric bimorph causing the piezoelectric bimorph to bend and contact a shorting electrode; shorting the capacitor and the piezoelectric bimorph and causing the piezoelectric bimorph to oscillate rapidly. Rapidly oscillating the piezoelectric bimorph causing a high voltage decaying signal to appear across the first and second bimorph electrodes. The method further comprises the step of applying polarity of a dc voltage to the piezoelectric bimorph causing it to bend towards said shorting electrode. After shorting the capacitor, the bimorph begins to vibrate because the voltage causing it to bend has fallen to zero.

About 70% of its stored mechanical energy can be recovered as electrical output.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For the present invention to be easily understood and readily practiced, the invention will now be described, for the purposes of illustration and not limitation, in conjunction with the following figures, wherein:

[0021] Figure 1 illustrates a nuclear battery schematic according to one embodiment of the present invention; [0022] Figure 2 illustrates a metalhydride;

[0023] Figure 3 illustrates LaNis Hydride/ D euteride;

[0024] Figure 4 is a chart of energy density versus power density for supercapacitors ;

[0025] Figure 5 illustrates one embodiment of the present invention using Zener voltage limiting diode; and

[0026] Figure 6 shows another embodiment of the present invention, including a piezoelectric bimorph with high voltage, high impedance and low voltage, low impedance outputs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0027] The invention will now be described in detail in relation to a preferred embodiment and implementation thereof which is exemplary in nature and descriptively specific as disclosed. As is customary, it will be understood that no limitation of the scope of the invention is thereby intended. The invention encompasses such alterations and further modifications in the illustrated apparatus and method, and such further applications of the principles of the invention illustrated herein, as would normally occur to persons skilled in the art to which the invention relates. [0028] A preferred embodiment of the present invention discloses the use of tritium loaded thin films 3 ("TLTF" or "TLTFs"). Metal tritirides are any metal hydrides where ordinary hydrogen has been replaced by the heaviest hydrogen isotope, tritium. A TLTF 3 is made by introducing tritium into, for example, magnesium thin films, which have been electroplated onto a metal strip of substrate. The magnesium is "hydrided" at a high temperature (approximately 325 ⁰ C) with the tritium isotope of hydrogen to form the TLTF. This composite TLTF 3 structure then makes up at least a part of one electrode of a radioactive capacitor, CN. The TLTF 3 is separated

from the facing counter metal electrode (CME) of the radioactive capacitor, CN, by a very thin air gap or optionally by a thin insulating material, such as but not limited to Mylar or Teflon. The material used is preferably thin enough to pass the electrons emitted by the TLTF. As the ³ H decays to ³ He by beta decay, the TLTF 3 acquires a positive charge and the facing CME becomes increasingly negatively charged by the electrons it acquires from the TLTF 3, causing a voltage, V _c , across radioactive capacitor CN- This process continues until the facing counter metal electrode, CME, acquires a sufficient negative voltage to repel the incoming electrons, whose energy distribution has an average energy of 4 keV. Other metals or alloys that can form a hydride, with a high mass density of hydrogen, include but are not be limited to, lithium hydride, lithium borohydride and lithium aluminum hydride. [0029] In a preferred embodiment of the present invention, as shown in FIG. 1, the capacitance of radioactive capacitor, CN, increase or scales with the TLTF 3 area and inversely to gap thickness, d _g . Since CN=C (A/ d) for parallel metal plates of area, A, separated by a gap, d _g , which is optionally filled by an insulator of permittivity, C. Supercapacitor, Cs, is in parallel with radioactive capacitor, CN, and clamping or Zener diode, Dc- The combination of the radioactive capacitor, CN, supercapacitor, Cs, and clamping or Zener diode, Dc is a nuclear battery, BN. Battery voltage, Vc, is determined by the voltage of the clamping or Zener diode, Dc. The battery, BN, is constantly being rapidly recharged by beta emissions from tritium due

to the very short time constant of the battery, B _N , circuit. Battery life is determined by initial tritium volume, i.e., the amount (thickness and area) of MgT2 initially formed on the TLTF 3 electrode, since the volume of tritium supplies the radioactive atoms that supply the battery, BN, energy as they decay.

[0030] In the present invention, the charge on the radioactive capacitor,

CN, can optionally be continuously moved for storage onto a much larger supercapacitor, Cs, which is placed in parallel with the radioactive capacitor, CN- Supercapacitor, Cs, can be charged to a suitably useful application voltage, VA, maintained by a clamping or Zener diode, Dc, placed in parallel with supercapacitor, Cs, through a protective series resistor, R _p , as shown in figures 1 and 5.

[0031] The radioactive capacitor, CN, is analogous to a leaky garden hose, which is dripping water into a very large bucket, whose maximum capacity is determined by a hole set in the side of the bucket at some height that determines the maximum level to which the bucket can be filled. The application voltage, VA, is determined by the clamping or Zener diode, Dc, which acts as the hole at a certain height in the side of the bucket. The larger the value of application voltage, VA, the larger the energy stored, Es, in supercapacitor, Cs, since Es = CSVA ² /2. In view of the present disclosure, a clamping diode has essentially the same function as a Zener diode. Both terms are used to describe the diode of the present invention and labeled herein as Dc.

[0032] For some embodiments of the present invention, e.g. automotive

batteries, it is desirable to have very large energies stored in supercapacitor,

Cs, so that there is a very large voltage across supercapacitor, Cs. This

voltage can then be chopped with a high voltage mulivibrator circuit to

create an alternating current that can then be passed through a step-down

transformer, rectified, and then used at a lower voltage to drive a starter motor.

[0033] Another preferred embodiment of the present invention uses a

Zener or clamping diode, Dc, to maintain a fixed voltage, as shown in FIG. 5. Zener or clamping diodes are designed to breakdown at a certain voltage reliably and non-destructively with voltage applied in the reverse direction. Thus, these diodes, Dc, can be used in reverse to maintain a fixed voltage across their terminals. Figure 5 shows a Zener or clamping diode, Dc, connected with a resistor, Rp, in series to limit the current. Zener and claiming diodes are rated by their breakdown voltage and maximum power - minimum voltage available is 2.7V. Power ratings of 40OmW and 1.3W are common.

[0034] Because the radioactive capacitor, CN, and supercapacitor, Cs, are in parallel, they each have the same voltage, V _A , determined by the choice of the Zener or clamping diode, Dc, and its clamping or stand-off

voltage. Therefore, V _A = QN/ C _N = Qs/ Cs, and Qs = QN (CS/ C _N ) , where Q _N and Qs are the charges on radioactive capacitor, CN, and supercapacitor, Cs, respectively. Supercapacitor, Cs, can be approximately 1 Farad (F), and

radioactive capacitor, CN, can be approximately 1 nano F < CN < 1 pico F,

and Qs can be approximately 10 ⁹ < Qs < 10 ¹² x QN. FIG. 4 shows the energy

density vs power density of some supercapacitors.

[0035] As discussed above, the combination of the radioactive

capacitor, CN, supercapacitor, Cs, and clamping or Zener diode, Dc,

constitutes a nuclear battery, BN, as shown in FIG. 1. The nuclear battery,

BN, is scalable because the size of the radioactive capacitor, CN, can be changed to a range of values by changing either the area of its electrodes or

changing the separation between the two electrodes. Supercapacitor, Cs, is also scaleable.

[0036] The nuclear battery, BN, of the present invention has a long life because tritium has a half-life of 12.3 years and the amount of tritium stored in the TLTF 3 can be varied by changing the thickness and area of its metal hydride layer. Calculations show that the time to charge a supercapacitor, Cs = 2 F with an equivalent series resistance (ESR) = 0.3 Ohms to approximately 300 V can be about 2 seconds for a radioactive capacitor, CN, with a 10 micrometers thick TLTF 3 and a gap, d _g , of 10 micrometers. [0037] One of the elements of the design of a nuclear battery, B _N , of the present invention is the choice of the metal matrix for storing the tritium. The objective of most hydrogen storage research is to find a material that stores a large weight percentage of H2 at a reasonable temperature (i.e. near room temperature) and pressure (i.e. near atmospheric pressure) and then

releases it rapidly at a somewhat higher temperature and pressure.

[0038] The material needed for the TLTF 3 in a nuclear battery, BN, has a different set of requirements. Here, a hydride material still must store a large weight percentage of Eb, but not release it readily at the operating temperature of most electronic equipment, which is usually well below 150 ⁰ C. Magnesium, which forms magnesium hydride at approximately 300 ⁰ C, is a promising candidate for TLTFs 3, which can be plated on a metal substrate. Other candidates for a TLTF 3 are lithium hydride, magnesium iron hydride, magnesium nickel hydride, sodium borohydride, lithium aluminum hydride and lithium borohydride. FIG. 2 illustrates a metalhydride in various hydriding stages. FIG. 3 shows pressure vs composition isotherms for a typical metal hydride material, lanthanum nickel five. The lower curves show the absorption of either hydrogen or deuterium into lanthanum nickel five with increasing pressure for a constant temperature of 40 °C. The upper curves show the release of hydrogen or deuterium as pressure is lowered at the same temperature of 40 ⁰ C. The desorption curves display hysteresis with respect to the lower absorption curves. Such hysteresis is useful for heat pump applications of metal hydrides, but is not particularly relevant to the present invention. The same type of absorption desorption curves apply to a magnesium hydride but a temperature of approximately 325 ⁰ C is required to form the hydride and the absorption desorption kinetics are much slower than is the case for lanthanum nickel five.

[0039] Tritium becomes a health hazard only when inhaled. The low energy electrons emitted from tritium cannot penetrate the skin. The present invention immobilizes and traps the tritium in a metal matrix for safety. The tritium cannot be released unless the ambient temperature exceeds approximately 325 ⁰ C. Optional steps can be taken to increase safety in conjunction with the present invention, such as using extremely small amounts of tritium in the TLTF 3.

[0040] In another preferred embodiment of the present invention, a circuit design of a nuclear battery, BN, with high voltage-high impedance and low voltage-low impedance outputs is shown in figure 6. 1 and 2 are metal electrodes of the nuclear battery, BN. A shorting metal electrode is shown at 13. The shorting metal electrode 13 is supported by support 12. The shorting metal electrode 13, can optionally consist of a spatially adjustable screw to vary the distance between 13 and 4. This distance varying changes the voltage and amount of energy stored by the piezoelectric bimorph. Support 12 and support 11 are rigidly connected to each other and can optionally be one solid piece.

[0041] One electrode 1 has a TLTF 3 disposed thereon. The TLTF layer

3 is located between the two electrodes 1 and 2. However, the TLTF 3 is only in contact with one electrode 1.

[0042] The invention further comprises a support 11 for a piezoelectric bimorph 6. Coil 8 has a signal induced by a magnet 7. Magnet 7 is located on the side of the piezoelectric bimorph 6 opposite from the shorting

electrode 13. The coil 8 optionally has a support (as shown in Figure 6) and/ or is rigidly connected to support 11. A power conditioning unit 9 provides low voltage, low impedance outputs while another power conditioning unit 10 provides for high voltage, high impedance outputs. [0043] The radioactive decay of tritium causes the radioactive capacitor,

CN, to charge quickly to a high voltage, which is then applied to the piezoelectric bimorph 6, to bend the bimorph 6 until it touches the shorting electrode 13. This shorts the radioactive capacitor, CN, and causes the bimorph 6 to oscillate rapidly. The rapid oscillations of the piezoelectric bimorph 6 causes a high voltage decaying signal to appear across the electrodes 4 and 5 of the piezoelectric bimorph 6. The same oscillation of the piezoelectric bimorph 6 also induces an AC signal in the coil 8 due to the magnet 7 attached to the piezoelectric bimorph 6. [0044] The shorting electrode 13 is to be spatially adjustable with a screw arrangement with respect to the piezoelectric bimorph electrode 4. This spacing variability varies the voltage to which the radioactive capacitor, CN, can be charged.

[0045] The power conditioning units 9 and 10 are rectifying units that permit a direct current output from an alternating current input. Charge can be stored at the output of the power conditioning units 9 and 10 on a capacitor or supercapacitor suitable for the voltage desired, i.e., the voltage rating of the capacitor should be suitable for the output voltage desired. The

polarity of the dc voltage applied to the piezoelectric bimorph 6 is chosen to cause the piezoelectric bimorph 6 to bend toward the shorting electrode 13. [0046] The energy stored, Es, due to a radioactive decay of tritium in the radioactive capacitor, CN, goes as Es= ¹ A CNV ² and the piezoelectric bimorph 6 can operate to at least a few thousand volts. Much more energy can be stored in the radioactive capacitor, CN, than is possible with the clamping or Zener diode embodiment where only a few hundred volts are preferably stored. After shorting the capacitor, the bimorph begins to vibrate because the voltage causing it to bend has fallen to zero. About 70% of its stored mechanical energy can be recovered as electrical output.

[0047] It is to be understood that standard semiconductor microchip fabrication methods may be used to form the supercapacitor, Cs, and the clamping or Zener diode, Dc, or piezoelectric bimorph 6 on the same chip in close proximity to the radioactive capacitor, CN. Alternatively, these may be separate components that are assembled to make the nuclear battery, BN.