WO2000055934A1

WO2000055934A1 - Movable anode fuel cell battery

Info

Publication number: WO2000055934A1
Application number: PCT/US2000/006729
Authority: WO
Inventors: William F. Morris; Tsepin Tsai
Original assignee: Reveo, Inc.
Priority date: 1999-03-15
Filing date: 2000-03-15
Publication date: 2000-09-21
Also published as: CN1186839C; US6458480B1; CA2368209A1; JP2002539597A; HK1046989B; CN1350707A; US6299998B1; TW474044B; HK1046989A1; EP1169745A1; KR20020019005A; AU3627900A

Abstract

A metal-air fuel cell battery (FCB) system having an electrolyte, and a movable anode having anode material deposited on two sides of an electrically conductive substrate, which can be either a rotating anode disk, or a linearly-movable anode, sandwiched between two air electrodes, wherein the air electrodes each have at least one recharging portion and at least one discharging portion. The recharging portion of the air electrode is designed for optimum recharging and the discharging portion of the air electrode is designed for optimum discharging such that the fuel cell battery performs to its maximum ability. The recharging air electrode area can be larger than the discharging air electrode area for faster recharge times. The recharging air electrode can be operated at lower current densities to prevent anode densification, anode shape change and dendrite growth. Discharging the anode material on both sides of the anode increases the depth of the discharge and increases the battery's capacity. The anode movement assures the anode is intermittently discharged to reduce passivation and further increases the depth of discharge. The motion of the anode helps to insure uniform replating during recharging. Futher, the movement of the anode stirs the electrolyte assuring a uniform distribution of metal ions. As a result, the invention provides a metal-air FCB system having high energy density, high power density and good rechargeability characteristics.

Description

MOVABLE ANODF FUEL CRT . BATTFRY

Applicant: Reveo, Inc .

BACKGROUND OF INVENTION

Technical Field

The present invention relates to improvements in metal-air fuel cell battery (FCB) systems and devices, and more particularly to a movable anode design for use in such systems and devices in order to obtai n improvements in charging and discharging of the anode structures employed therein .

Background Art

The use of metal-air FCB systems and devices for electrical power generation offers great promise for the future of m anki nd .

US Patent Number 5,250,370 to Fans discloses an exemplary metal- air FCB system. According this metal-air FCB system design, a bifunctional air electrode is arranged on one side of a rotating anode structure, for carrying out discharging and recharging operations. Also, WIPO Publications WO 99/ 1 8627, WO 99/ 18628 and WO

99/ 18620 by Applicant disclose various types of metal-air FCB systems employing moving anode and cathode structures which can be used t o generate electrical power for a variety of applications using a metal, s uch as zinc, and air as fuel . However despite the incredible advances that such metal-air FCB systems represent to the electrical power industry, there nevertheless remain a number technical p roblems which limit the recharging performance of

such electrical power generation systems. In large part, such problems are due to a number of factors, including: (i) the deformation of shape/geometry of the anode structure; (ii) densification of the anode structure; and (iii) formation dendrites on the anode structure which reach through the separator, touch the air electrode, and eventually short out the cell. In general, such anode related problems have limited the operational life of prior an rechargeable FCB systems and devices. Hitherto, prior art solutions to these problems have typically involved decreasing the current density of the anode structure during both discharging and recharging operation, as well as the depth of discharge thereof. Both of these side-effects have severely limited th e energy and power density characteristics of prior art metal-air FCB systems. Thus, in prior art metal-air FCB systems and devices, there has been a serious trade off between achieving high energy/power densities and good charging characteristics.

Also, when using prior art techniques, it has not been possible to construct a bifunctional air electrode for use in metal-air FCB systems which operates in an efficient manner during both recharging a n d discharging operations. Another problem with prior art FCB systems is that the anode structure undergoes deformation during the lifetime of the system. When the anode undergoes deformation during each recycling/recharging operation, the capacity of the system decreases significantly, and shorting problems often occur. One attempt to solve the anode deformation problem has been t o use a reticulated sponge-like zinc anode in order to increase the surface area of the zinc (and thus decrease the current density therewithin). However, the lowered current density decreases the energy density of the FCB system. Also, the use of a reticulated sponge-like zinc anode does n o t prevent the growth of dendrites on the anode.

Attempts by others have been made to limit dendrite growth o n reticulated zinc anode structures. One approach has involved using a chemically inert coating on the exterior of the anode structure. While this reduces dendrite growth, the loss of the anode area , lowers the capacity of the cell.

Prior art attempts to reduce anode deformation have involved t h e use of a pump to circulate the electrolyte. By continually stirring the electrolyte within the cell, a more uniform distribution of zinc ions i n solution will result. A uniform mixture of zinc ions in the electrolyte can greatly reduce anode shape deformation over repeated cycling.

U.S. Patent 3,663,298 discloses a method of reducing anode shape deformation and dendrite growth. According to this prior art approach, zinc pellets and electrolyte are u sed to fill about 2/3 of the volume of a circular rotating drum, on the walls of which the air electrode is formed. The drum rotates during discharging and recharging operations, and th e zinc particle bed continually mixes within the cell. Because the particles move freely, fresh zinc continually and evenly is exposed to the air electrode. By evenly depositing zinc during recharging operations, a longer discharge life can be achieved at higher current densities.

U.S. Patent 3,663,298 discloses that the use of a rotatable electrode improves the recharging characteristics of metal-air FCB systems. As disclosed, this technique enables repeated recharging and discharging a rotating electrode at rates up to 100 m A/c nr. Conventional zinc electrodes do not ordinarily withstand recharge rates in excess of 2 0 m A/c m² on repeated cycling without rapid failure by dendrite shorting. The high recharging rates were possible because the continual movement of the particle bed provided for a smooth, dendrite free, zinc coating o n the pellets.

While rotatable electrode concept of U.S. Patent 3,663,298 improved upon conventional zinc/air FCB technology, it required the use of a n inefficient bifunctional air electrode. Bifunctional air electrodes have very low cycle numbers because th e electrode has to be used both for charging and discharging. Bi-functional electrodes are inefficient for discharging because they m u s t simultaneously be optimized for recharging. In addition, prior art bifunctional electrodes are generally t hick and heavy, to slow down degradation processes. Their significant weight and size reduces the energy density of the system. In the past, others have tried using m an y different catalysts and different electrode structures to make bifunctional air electrodes with improved performance characteristics, but the lives of prior art rechargeable zinc-air FCB systems have been severely limited. In the Sony Corporation publication entitled "Fuel Cell and their Application" published in 1996 (at pg. 160), there is disclosed a rechargeable metal/air FCB system design employing a third electrode.

This FCB system comprises a zinc anode sandwiched between one recharging air electrode and one discharging air electrode. This prior art approach to metal-air FCB construction sought to eliminate the need for a bifunctional air electrode. According to the approach, the zinc anode would be discharged from one side and recharged from the opposite side, while using different discharging and recharging electrodes that are optimized for their independent functions.

While Sony's zinc/air cell was an improvement on the bifunctional air electrode, the zinc anode could only be discharged form one side, th u s reducing the power capabilities of the cell by 50%. Further, the zinc anode is charged from the side where it was discharged the least, which decreases the efficiency of the system.

Another problem presented by the Sony design is that the anode h as to be a porous structure so that the electrolyte can flow from th e discharge side to the recharge side to provide ions in solution from discharging in order to recharge again .

Thus, there is a great need in the art for an improved way of a n d means for producing electrical power using a rechargeable metal-air FCB system having high energy density, high power density, and good rechargeability, while overcoming the shortcomings and drawbacks of prior art technology. DISCLOSURE OF THE INVENTION

Accordingly, it is a primary object of the present invention is t o provide an i mproved rechargeable metal-air FCB system having h igh energy density, high power density, and good rechargeability.

Another object of the present invention is to provide a metal-air FCB system having metal anodes which do not undergo any significant shape deformation (i.e. change) during charging and discharging operations, i n order to ensure a longer battery life. Another object of the present invention is to provide such a metal- air FCB system, wherein dendrite formation on metal anodes is controlled.

Another object of the present invention is to provide such a metal- air FCB system having a fast recharging capability.

Another object of the present invention is to provide a metal-air FCB system having an increased turnaround efficiency for recharging th e anode structures employed within such a system.

Another object of the present invention is to provide such a metal- air FCB system, wherein the anode structure is realized in the form of a disc structure on which metal fuel material is supported. In accordance with one aspect of the present invention, a novel metal-air FCB system is provided, wherein a movable anode is sandwiched between two stationary air electrodes. The air electrodes are divided into a recharge air electrode portion, to maximize recharging of the an ode structure, and a discharge air electrode portion for maximizing the discharging of the anode structure. The anode structure is moved ei ther rotationally or linearly with respect to the air electrodes; exposing portions of the anode alternately to the recharging and discharging portions of the air electrode. Electrolyte fills the space between the air electrodes and the movable anode structure. Previous solutions to the metal/air rechargeability problem could only increase cycle life at t he expense of decreasing energy and power densities. In marked contrast, the movable anode FCB system of th e 00/55934 PCT/USOO/06729 ___ present invention has both increased cycle life and discharge performance. Recycleability is increased for the following reasons.

The recharging electrode of the present invention is intended solely for recharging operations, and thus there is no need to use a bifunctional air electrode. An air electrode intended solely for recharging operations will not limit the lifetime of the cell. The cycle life of the cell will b e limited by the lifetime of the anode structure.

The electrolyte in each cell of the FCB system is continually stirred during recharging operations. The stirring action creates an even distribution of zinc ions in solution. This r esults in an even plating on th e zinc anode, which greatly reduces the anode shape deformation.

In accordance with the present invention, the anode structure of the FCB system is continually moving during recharging operations, which greatly reduces d e n d rite growth and anode shape deformation. These phenomena occur because of an uneven electric field distribution on the zinc surface. If one spot has a lightly higher electric field than another, this spot will continually attract zinc ions. However, with the anode moving, the point of peak electric field will be changing positions a n d moving in and out of the recharging area; reducing the chances of localized buildup. If the movement alone does not stop dendrite growth, they can be removed mechanically by a stationary wiper attached to th e air electrode holder. A the anode moves past this wiper, the dendrites will be smoothed out or scraped off.

The recharging air electrode of the present invention can be several times larger than the discharging air electrode. This will allow for fast recharging operations, while still using a low current density. In prior art fixed anode FCB systems, the only way to decrease charging time was t o increase charging current density. High charging current density significantly decreases cycle life, and turnaround efficiency which is defined as a ratio of the power output of a cell and the power required t o charge it. A decreased turnaround efficiency implies less electrical power is required to charge the cell. In the metal-air FCB system of the present invention, high energy density is obtained for the following reasons.

The design of the movable anode FCB system of the present invention allows the weight of the cell to be dominated by the metal anode. Consequently, the energy density of the cell has the ability to approach that of the metal anode.

The movable anode FCB system of the present invention has the ability to increase energy density by increasing the anode's depth of discharge (DOD). This means a greater percentage of the anode can b e discharged. The movable Anode FCB system can increase ODD because i t limits passivation. An anode will passivate if too much current is d rawn from it in too short a time. Passivation can be substantially decreased if the anode is discharged intermittently (in other words, allowing the an ode to rest between discharging can eliminate passivation). The movable anode FCB system of the present invention will do exactly that. As each anode section moves away from the discharge electrode, it has a rest period before it is discharged some more, in addition, because of the moveable Anode's' unique recharging capabilities, the anode can afford t o be discharged to a high DOD without sacrifice of cycle life whereas most recharging batteries must limit their DOD to ensure reasonable recycleability.

The discharging air electrode in the FCB system of the present invention is intended solely for carrying out discharging operations, a n d therefore, there is no need for the use of bi-functional air electrodes. This implies that the discharge electrode can be optimized exclusively for discharging.

Preferably, the electrolyte in each cell of the metal-air FCB system of the present invention is continually stirred during discharging operations. By stirring the electrolyte, it is possible to increase its capacity, implying that less electrolyte is needed, which translates to a higher energy density.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the objects of the present invention, the following Best Modes For Carrying Out The Present Embodiments set forth below should be read in conjunction with th e accompanying Drawings, wherein: Fig. 1 is a top view of the anode disk of the present invention;

Fig. 2 is a side view of the anode disk of the present i nvention ; Fig. 3 is a top view of the air electrode disk of the present invention ; Fig. 4 is a side view of the air electrode disk of the present invention; Fig. 5 is a side view of a rotating anode cell of the present invention;

Fig. 6 is a perspective view of a plurality of rotating anode cells making up a fuel cell battery of the present invention;

Fig. 7 is a side view of an anode plate of the present invention ; Fig. 8 is a top view of an anode plate of the present invention; a n d Fig. 9 is a side view of a linear anode cell of the present invention;

BEST MODES EMBODIMENTS OF THE PRESENT INVENTION

Referring now to the Figs, in the accompanying drawings, the best mode for carrying out the present invention will be described in detail, wherein like elements will be indicated in Figs, with like reference numerals.

As shown in Figs. 1 and 2, the first component in the metal-air FCB system of the invention comprises an anode disk structure 1 1 which has a current-collecting anode substrate 12 made o ut of a metal such as nickel or other electrically conductive material which is resistant to corrosion i n basic solutions. The current collecting anode substrate 12 has a layer of anode material 13, which may be a metal such as zinc deposited on the current collecting anode substrate 12. The anode disk 1 1 has an axle 1 5 on which it can be rotated. The rotation of the disk can be by gears 1 6, and motor 17 as shown in Fig. 5, engaging teeth 14 on the anode disk 1 1 or by motor 17 and drive shaft 47 turning gears 16, engaging teeth 14 o n anode disk 1 1 as shown in Fig. 6.

As shown in Figs. 3 and 4, the second components in the metal-air FCB system of the invention are air electrode disks 21 which are a little bi t larger in diameter than the anode disk 1 1. The air electrode disks 21 are divided into discharging air electrode potions 23 and recharging air electrode potions 24. The discharging air electrode potions 23 may be of different sized and located in different positions on the air electrode disk 21 to m aximize the utility of the designed rates for discharging depending on the types of anodes air electrodes and electrolyte used. The recharging electrode portions 24 may be of different sizes and geometries and located into different positions on the air electrode disk 21 to maximize the utility of the designed rates for discharged depending on the types of anodes air electrodes and electrolytes used. For example, the electrode portions 24 could be arranged radially about the disc 21, they could be concentrically arranged about the disc 21 , or any other arrangement consistent with t h e principles of the present invention.

If more than one set of recharging air electrodes 23 are used in th e FCB system, as shown in Fig. 4, then the anode disk 1 1 can be recharged i n two or more different portions simultaneously. Similarly, if more than o ne set of discharging air electrodes 24 are used in the FCB system, as shown in Fig. 4, then the anode disk 1 1 can be discharged in two or more different potions of the anode d isk 1 1 simultaneously.

The air electrode disks 21 may have axle slots 22 for inserting th e axle 15 of the anode disk 1 1 between two air electrode disks 21 so that th e anode disk 1 1 is rotatable on its axle 15 when sandwiched between two ai r electrode disks 21 as shown in Fig. 5. The axle slots 22 in the air electrode disks 21 allows the anode disk 1 1 to be changed from time to time b y sliding the old anode disk 1 1 out and inserting a new anode disk 1 1 .

In an alternative embodiment, the anode disk 1 1 may b e permanently fixed between the air electrode disks 21 so that no axle slot 22 is required.

Fig. 5 shows a complete secondary fuel cell battery (FCB) cell 40 i n accordance with the present invention. It has an anode material 13, a discharge electrode portion23, electrolyte 35 and wires 37 and 38 for connecting current generated in the cell 40 to a load. The cell 40 also h as a recharging air electrode portion 24 and wires 37 and 39 for supplying current to the cell to recharge the anode material 13. A motor 17 an d associated drive gear 16 attached between the air electrode disk 21 engage the gear teeth 14 on the anode disk 1 1 for rotating the anode disk 1 1 between the two air electrode disks 21. A seal 30 extending between the air electrode disks 21 at t he circumference forms a container with the walls of the air electrode disks 21 for containing electrolyte 35 needed for the fuel cell battery to complete a battery circuit. The seal 30 may have an aperture 56 at the top for adding electrolyte 35 to the cell formed b y the anode material 13 and air electrode disk 21 for removing an d replacing the anode disk 11. In an alternative embodiment of the present invention, the seal 30 does not cover the top of the cell 40 leaving th e motor and gears exposed and allowing easy access for adding electrolyte 35, however, the cell 40 must be upright and is subject to spillage of electrolyte 35. The motor 17 may be driven at different speeds to maximize recharging or discharging rates. The motor 17 may optionally be outside of the cell 40.

To increase the power of the metal-air FCB system hereof, a n u mbe r of cells 40 can be joined together. In this way a high voltage can b e achieved from the system. In Fig. 6 a plurality of cells 40 are shown linked together on a common drive shaft 47. Optionally the individual motors of Fig. 5 may b e used to drive each anode disk 1 1 in each cell 40 separately.

As shown in Fig. 6, the discharge air electrode portions 23 a n d recharging air electrode portions 24 may be clocked (i.e. controllably timed) for air management purposes. The air flowing to the discharge electrode portions 23 or from the recharging air electrode portions will benefit from being clocked in such a manner.

In Fig. 6, the drive shaft 47 will conduct electricity to and from the anode disks 1 1 by contact with driving gear 16 and gear teeth 14 on the conducting anode substrate 12. A wire 37 connects the drive shaft 47 to the controller 50. Wire 38 connects the discharge air electrode portions 23 of the cell 40 to the controller 50. Wire 39 connects the recharge ai r electrode portion 24 of the cell 40 to the controller 50. The controller 5 0 controls the speed for the motor 17, in Fig. 6, or the motors 17, if the cells of Fig. 5 are used.

In an alternate embodiment of the anode disk 1 1 shown in Fig. 5 , the anode substrate 12 can be connected through axle 15 to electrical contact 34 on the air electrode disk 21 , where wire 36 will connect the anode disk 1 1 to the controller 50.

Applicant teaches various methods of and systems for managing th e amount of charge stored in a fuel cell battery and the measurement of the rates of charging and discharging, in the following WIPO Publications Nos.: WO 99/18627 entitled "Metal-Air Fuel Cell Battery System Employing Metal-Fuel Tape"; WO 99/18628 entitled "Metal-Air Fuel Cell Battery

Systems Employing Metal-Fuel Cards"; and WO 99/18620 entitled "Metal- Air Fuel Cell Battery Systems Employing Moving Anode And Cathode Structures", each incorporated herein by reference in its entirety, as if set forth fully herein. In accordance with the teachings of these WIPO Publications, controller 50 can measure the current flows and other parameters with various sensors, knows the availability of the charge stored on the anode disk 1 1 and what portion of the disk the charge is stored on. The controller will then manage the discharging a n d recharging the anode disk 1 1 to optimize performance of the cells 40 t o provide power to a load or to recharge the cells.

A check valve 5, as shown in Fig. 5, may be used on the top of the cell 40 to exhaust oxygen created during recharging, if the oxygen level i n the cell increases the pressure of the cell.

An electrolyte refilling port 56 may be located on the top of the cell 40 to replace electrolyte which is spilled leaked or otherwise escapes from the cell 40. Optionally, the cell 40 may not be sealed at the top for easier access to replace the anode disks 1 1 or for adding electrolyte.

The operation of the rotating anode device described above h as many a dvantages over the prior art.

The air electrode disk 21 has separate discharge air electrode portions 23 and recharge air electrodes portions 24. by not using bifunctional air electrodes the recharging air electrode 24 and the discharge air electrode 23 can be optimized for the most efficient discharging or recharging of the anode material 13 on the anode disk 1 1 . With a bi-directional motor 17 the anode disk can be turned backward o r forward to operate in the most efficient zones on the anode disk 1 1, s uc h that on discharging the anode disk 1 1 1 will be rotated to a position where the most charge is stored or on recharging the disk will be rotated t o where the least charge is stored. With a motor speed controller 52 th e motor 17 can turn the anode disk 1 1 at the optimum rate to charge o r discharge the anode disk 1 1 .

The surface areas of the discharge air electrode 23 and the recharge air electrodes 24 can be varied to vary the charging to discharging ratio. For example with a ratio of charging to discharging surface area of the air electrodes of 10 to 1 the recharging can take place 10 times faster th an the discharging. If the rotating anode fuel cell battery is used for powering a vehicle, fast recharging times may be very important. Depending on the type of discharge air electrode 23 chosen for discharging the anode material 13, the discharge rates of the anode material 13 will vary, many factors effect the discharge rate in a fuel cell battery cell, they include but not are not limited to the electrolyte 3 5 used, the spacing between the discharge air electrode 23 and the anode material 13, and the rate at which the anode material 13 is passing i n front of the discharge air electrode 23. For example in the art of zinc-air battery cells, various types of anodes and air electrodes have been used i n combination. Some air electrodes are better at recharging than for discharging. If the best discharge air electrode 23 is placed on the air electrode disk 21 opposite the anode material 13 on the anode disk 1 1 and a specified electrolyte 35 is used, the discharge parameters of the system can be maximized for the spacing between the air electrode disk 2 1 and anode disk 1 1 for the types of anode materials 13 and discharge air electrodes 23 used.

Similarly for recharging, if the best recharging air electrode 24 is placed on the air electrode disk 21 opposite the anode material 13 on the anode disk 1 1 and a specified electrolyte 35 is used, then the recharge parameters of the system can be maximized for the spacing between the air electrode disk 21 and anode disk 1 1 for the types of anode materials

13 and recharge air electrodes 24 used .

Individually maximized air electrodes function better than the bifunctional air electrodes of the prior art systems. The individually maximized air electrodes for recharging will increase the lifetime of the cell by limiting shape change, densification and dendrite problems in the cell.

One reason for the reduction in the anode shape deformation, densification, and dendrite problems is that the recharging is performed over a larger surface area at lower current densities so that the anode material 13 is applied at a slower rate and does not build up quickly i n any one place. Further, since the anode is rotating and the electrolyte 3 5 is being stirred by the motion of the rotating anode disk 1 1 , the an ode material is applied more evenly.

Dendrites grow because anode ions are continually attracted to o n e point on the anode. Since the anode is moving, that point will b e changing positions reducing he chances of localized buildup. If the movement of the anode does not totally stop the dendrite growth a wiper blade 28 can be attached to the air electrode disk 21 at the edge of the recharging air electrode portion 24 to scrape off t he dendrites.

The rotating anode is scalable, the diameters of the anode disks 1 1 and the air electrode disks 21 may be increased or decreased to fit t h e design needs of the user. For example, a small vehicle such as a motor bike would have a smaller diameter rotating anode, than a car or a truck.

By rotating the anode disk 1 1 between two air electrode disks 21 th e depth of discharge (DOD) of the anode disk 1 1 is increased because i t limits passivation. An anode will passivate if too much current is draw n from it in too short a time. Passivation can be substantially decreased if the anode is discharged intermittently (in other words, allowing the anode to rest between dischargings can eliminate passivation). The Movable Anode PCB will do exactly that. As each anode section moves away from the discharge electrodes, it has a rest period before it is discharged some more. In addition, because of the Movable Anode's unique recharging capabilities, the anode can afford to be discharged to a high DOD wi thout sacrifice of cycle life, whereas most recharging batteries must limit their DOD to ensure reasonable recycleability. In a second embodiment of the invention, as shown in Figs. 7, 8 a n d

9, the anode material 1 13, instead of being rotated between two ai r electrode disks 21, is moved linearly between two air electrode plates 1 2 1 as shown in Fig. 9.

As shown in Figs. 7 and 8, anode plate 1 1 1 has an anode substrate 1 12 with anode material 1 13 thereon .

Fig. 9 shows two air electrode plates 121 each having discharging ai r electrode portions 123 and recharging air electrode portions 124. Wires 138 and 139 connect the controller 150 to the discharging 123 a n d recharging 124 air electrodes respectively. Wire 137 connects the controller 150 to the anode plate 1 1 1 by way of the link arm attached t o the anode plate hitch 1 15. Guide wheels 120 ride on the wheel track 1 1 4 portion of the anode plate 1 1 1 to moveably hold the anode plate 1 1 1 between the wheel guides 120. The link arm 126 is attached to a crank shaft 1 30 for moving the anode plate 1 1 1 back and forth relative to the discharging air electrode portions 123 and recharging air electrode portions 124 of the air electrode plates in electrolyte 135 to charge a n d discharge the anode material 1 13 as outlined above. The discharging ai r electrode portions 123 may be opposite recharging air electrode portions 124 as shown in Fig. 9 or opposite a like air electrode portions. A motor 1 17 or other means of turning the crank shaft 130 is controlled b y controller 150. Wires 140 connect the controller to the motor 1 1 7. Having described in detail the various aspects of the present invention described above, it is understood that modifications to the illustrative embodiments will readily occur to persons with ordinary skill in the art having had the benefit of the present disclosure. All such modifications and variations are deemed to be within the scope and spirit of the present invention as defined by the accompanying Claims t o

Invention.

Claims

CLAIMS TO INVENTION:

1 . A movable anode fuel cell battery comprising: two air electrodes, each having at least one recharging air electrode portion and at least one discharge air electrode portion; a metal anode having a substrate with a metal anode material o n either side of the substrate disposed proximate to and between the two ai r electrodes and moving with respect to thereto, an electrolyte for contacting the air electrodes and anode material to form a cell, a means for moving the anode material relative to the recharging ai r electrode portion for recharging the anode material and for moving th e anode material relative to the discharging air electrode portion for discharging the anode material.

2. A movable anode fuel cell battery as in claim 1 wherein : a controller connected to the means for moving the anode in order to control the speed and direction of the anode's motion.

3. A rotating anode fuel cell battery as in claim 1 wherein : the recharging air electrode area has a greater area than the discharging air electrode area such that recharging the anode will b e faster than discharging and at a lower current density.

4. A movable anode duel cell battery as in claim 1 wherein : a wiper blade attached to the air electrode, adjacent to the recharging air electrode portion, for contacting the anode such that dendrites on the anode disk will be scraped off the mode by the wiper blade as the anode moves relative to the wiper blade.

5. A movable anode fuel cell battery as in claim 1 wherein there is: a means for replacing the metal anode for mechanically recharging the fuel cell battery with new metal anodes.

6. A movable anode fuel cell battery as in claim 5 wherein : the air electrodes have axle slots the metal anode having an axle such that the axle engages in th e axle slots for removing and replacing metal anodes. 00/55934 PCT/USOO/06729 _____

7. A movable anode fuel cell battery as in claim . 1 wherein : the anode material rotates relative the air electrodes.

8. A movable anode fuel cell battery as in claim 1 wherein: the anode material moves linearly relative to the air electrodes.

9. A movable anode fuel cell battery as in claim 1 wherein : a plurality of movable anode fuel cells operate simultaneously such that their combined electrical output is delivered to a load.

1 0. A movable an ode fuel cell battery as in claim 9 wherein : a motor drives a common drive shaft connected to all anodes in the fuel cells such that the drive shaft moves all the anodes at the same time.

1 1 . A movable anode fuel cell battery as in claim 9 wherein: each a node fuel cell has a separate motor to drive the anode independently of other anodes.

12. A movable anode fuel cell battery as in claim 1 1 wherein: a controller controls each motor such that the speed and direction of each anode in each cell is controlled to maximize the efficiency of the fuel cell battery .

13. A movable anode fuel cell battery as in claim 9 wherein : the plurality of cells are adjacent to each other and the recharging and discharging air electrodes for each cell are clocked with respect to the adjacent cells for air management.

14. A movable anode fuel cell battery (FCB) system comprising: two air electrodes, each said electrode having at least o ne recharging air electrode portion and at least one discharge air electrode portion ; a metal anode having a substrate with a metal anode material disposed on either side of said substrate, and said substrate being disposed proximate to and between said two air electrodes and moving with respect to thereto ; an electrolyte for contacting said air electrodes and said metal anode material to form a cell; a n d a first mechanism for moving the anode material relative to said recharging air electrode portion for recharging said anode material, a n d for moving said anode material relative to said discharging air electrode portion for discharging said anode material.

15. The movable anode FCB system of claim 14, wherein : a controller connected to the means for moving the anode in orde r to control the speed and direction of the anode's motion.

16. The movable anode FCB system of claim 14, wherein : the recharging air electrode area has a greater area than the discharging air electrode area such that recharging the anode will b e faster than discharging and at a lower current density.

17. The movable anode FCB system of claim 14, wherein: a wiper blade attached to the air electrode, adjacent to the recharging air electrode portion, for contacting the anode such that dendrites on the anode disk are scraped off the mode by the wiper blade as the anode moves relative to the wiper blade.

18. The movable anode FCB system of claim 14, which further comprises: a second mechanism for replacing said metal anode for mechanically recharging the fuel cell battery with new metal anodes.

19. The movable anode FCB system of claim 18, wherein: said air electrodes have axle slots the metal anode having an axle such that the axle engages in the axle slots for removing and replacing metal anodes.

20. The movable anode FCB system of claim 14, wherein : the anode m aterial rotates relative the air electrodes.

21. The movable anode FCB system of claim 14, wherein : the anode material moves linearly relative to the air electrodes.

22. The movable anode FCB system of claim 14, wherein : 00/55934 PCT/USOO/06729 ___

a plurality of movable anode fuel cells operate simultaneously s uch that their combined electrical output is delivered to a load.

23. The movable anode FCB system of claim 22, wherein : a motor drives a common drive shaft connected to all anodes in the fuel cells such that the drive shaft moves all the anodes at the same time.

24. The movable anode FCB system of claim 22, wherein : each anode fuel cell has a separate motor to drive the an ode independently of other anodes.

25. The movable anode FCB system of claim 24, wherein : a controller controls each motor such that the speed and direction of each anode in each cell is controlled to maximize the efficiency of th e fuel cell battery .

26. The movable anode FCB system of claim 22, wherein : the plurality of cells are adjacent to each other and the recharging and discharging air electrodes for each cell are clocked with respect to th e adjacent cells for air management.

27. A rechargeable metal-air fuel cell battery (FCB) system comprising: two air electrodes, each having at least one recharging portion a n d at least one discharging portion ; a movable anode having anode material deposited on two sides of an electrically conductive substrate, and being sandwiched between said two air electrodes with an electrolyte disposed between said an ode material and said recharging portions and said discharging portions.

28. The rechargeable metal-air FCB system of claim 27, wherein said recharging portion of each said air electrode is designed for opti mum recharging operations, and said discharging p ortion of said air electrode i s designed for optimum discharging operations.

29. The rechargeable metal-air FCB system of claim 27, wherein t h e recharging air electrode area is larger than the discharging air electrode area for faster recharge times. 00/55934 PCT/USOO/06729 _____

30. The rechargeable metal-air FCB system of claim 27, wherein said recharging air electrode is operated at lower current densities to prevent anode densification, anode shape change and dendrite growth.

31. The rechargeable metal-air FCB system of claim 27, wherein said discharging said anode material on both sides of said movable anode increases the depth of the discharge and increases the capacity of said FCB system.

32. The rechargeable metal-air FCB system of claim 27, wherein movement of said movable anode assures said anode material is intermittently discharged to reduce passivation and further increases the depth of discharge of said anode material .

33. The rechargeable metal-air FCB system of claim 27, wherein th e motion of said movable anode helps to insure uniform replating during recharging operations.

34. The rechargeable metal-air FCB system of claim 27, wherein the movement of said anode stirs the electrolyte assuring a uniform distribution of metal ions.

35. The rechargeable metal-air FCB system of claim 27, wherein said movable anode is realized in the form of a rotating anode disk.

36. The rechargeable metal-air FCB system of claim 27, wherein said movable anode is realized in the form of a linearly moving anode, sandwiched between said two air electrodes.