Patent Publication Number: US-2021184297-A1

Title: Metal air battery device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and is a non-provisional of U.S. Patent Application 62/720,959 (filed Aug. 22, 2018), the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to metal air batteries. Metal air batteries provide high energy density power sources that show promising applications as mobile and stationary distributed power sources. The batteries have the potential to replace the internal combustion engines found in hybrid cars and aircraft since the energy density, efficiency of conversion approach those of hydrocarbon fuels. 
       FIG. 1  depicts a schematic representation of a conventional aluminum-oxygen cell system  100 . The system  100  comprises an air metal battery  102 , an air blower  104  or an oxygen supply  106  and a carbon dioxide scrubber  108 . An electrolyte tank  110  with a filter  112  is also present. A coolant system with a heat exchanger  114  and pump  116  is provided. An electrolyte pump  118  sends electrolyte through the air metal battery  102  and a gas separator  120 . A knockout tank  122  and hydrogen disposal system  124  are also present. A specific air battery cell is shown in  FIG. 2 . 
       FIG. 2  depicts a portion of the air metal battery  102  in further detail. A metal anode  200 , an electrolyte  202  and an air breathing cathode  204  is shown. The air breathing cathode  204  may contain a conductive charge collecting screen embedded in a conductive matrix that contains a catalyst that promotes the reduction of oxygen. There is a hydrophobic layer that is porous to gas but not the liquid electrolyte. The oxygen needed for the chemical reaction can penetrate the air breathing cathode  204  but still hold the liquid electrolyte in place against the surface of the anode. The metal anode  200  is made from a variety of metals such as zinc, magnesium, iron and aluminum. In one embodiment, the metal anode  200  is aluminum due to the low cost and density of the material. 
     The metal anode is consumed during the operation of metal air batteries and causes some issues with performance and reliability of the system. When the electrical circuit in a metal air battery is interrupted (turned off) the electrolyte reacts instantly with the metal to produce dangerous volumes of hydrogen gas that must be vented from the battery system. The hydrogen bubbles collect in the electrolyte rapidly and increase the electrical resistance of the battery so that even if the battery is quickly turned back on full power is not available until the electrolyte with hydrogen bubbles is flushed from the system. This pumping and flushing of the electrolyte requires a “knockout” system that separates gas and liquid so hydrogen gas can be safely removed from the system. Knockout system normally uses some type of cascade of liquid through baffles to allow for departure of gas out of solution. Attempts to drain the electrolyte out of a metal air battery does shut down the power output but has been found to result in small droplets and liquid film coatings of the metal anode that produce large amounts of hydrogen gas and corrode the metal unevenly producing pits and voids that reduce the efficiency and amount of power available from the system. As a result of these problems all metal air batteries are designed to be turned on and run until the metal anode is spent. In summary it is very difficult to turn off a metal air battery and then turn it on again without damage to the complete system so they are left on for the lifetime of the anode. 
     The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
     SUMMARY 
     A metal air battery system comprised of anode/cathode assembly with air gun plenums mounted on both sides of the anode. The anode is mounted in a battery cell chamber that holds the anode parallel with the cathode. The anode is able to move in and out of the battery cell chamber while the air gun plenums emit high pressure air for the purpose of wiping clean liquid electrolyte from the surface of each anode to provide for rapid shutdown of chemical reactions that produce hydrogen gas and electric current. 
     In a first embodiment, a method for halting operation of a metal air battery is provided. The method comprising: withdrawing an anode from a battery cell chamber such that less than 20% of a length of the anode remains within the battery cell chamber, wherein the anode is a rectangular block with a first flat surface and a second flat surface, the first flat surface and the second flat surface being opposite; the battery cell chamber comprises a slot for receiving the anode; a first cathode plate that is parallel and proximate to the first flat surface of the anode, thereby forming a first electrolyte chamber; a second cathode plate that is parallel and proximate to the second flat surface of the anode, thereby forming a second electrolyte chamber; a first air gun plenum and a second air gun plenum, each disposed at the top of the battery cell chamber and on opposing sides of the anode; supplying pressurized air to the first air gun plenum and the second air gun plenum, thereby supplying air flow to the first flat surface and the second flat surface, respectively; wherein the step of withdrawing and the step of supplying occur simultaneously such that electrolyte is removed from the first flat surface and the second flat surface and pushed into the first electrolyte chamber and the second electrolyte chamber, respectively, and thereby halting operation of the metal air battery. 
     In a second embodiment, an air metal battery is provided. The air metal battery comprising: an anode that is a rectangular block with a first flat surface and a second flat surface, the first flat surface and the second flat surface being opposite; a battery cell chamber comprising: a slot for receiving the anode; a first cathode plate that is parallel and proximate to the first flat surface of the anode, thereby forming a first electrolyte chamber; a second cathode plate that is parallel and proximate to the second flat surface of the anode, thereby forming a second electrolyte chamber; a first air gun plenum and a second air gun plenum, each disposed at the top of the battery cell chamber and on opposing sides of the anode. 
     This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the invention encompasses other equally effective embodiments. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the features of certain embodiments of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. Thus, for further understanding of the invention, reference can be made to the following detailed description, read in connection with the drawings in which: 
         FIG. 1  is a schematic depiction of a system that utilizes a metal-air battery; 
         FIG. 2  is schematic of a metal-air battery; 
         FIG. 3  depicts an anode for use with a battery cell chamber; 
         FIG. 4  depicts a cathode for use with the battery cell chamber; 
         FIG. 5  depicts the battery cell chamber; 
         FIG. 6  depicts the battery cell chamber in use showing the anode being withdrawn; and 
         FIG. 7  depicts the battery cell chamber with the anode and cathode plate inserted. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present disclosure pertains to a metal air battery that provides for complete rapid shutdown of power without parasitic corrosion and production of dangerous hydrogen gas. It also provides for the rapid restart to full power and production of constant power output throughout the consumption of the metal anode. Some embodiments of the disclosed air battery provide for a low-cost metal anode configuration that does not need high integrity edge seals and that can be automatically loaded into the metal air battery system for the purposes of extended operation. 
     The anode/cathode configuration of the disclosed metal air battery and its dynamic operation provide solutions to many conventional problems outlined in the background above. The battery can use a variety of metal anodes such as zinc, lithium, iron etc. In one embodiment, the metal used is aluminum due to low cost, weight and easy availability with low environmental impact in production and storage. 
     Referring to  FIG. 3 , in one embodiment, the battery comprises a rectangular anode  300  of aluminum bonded to a plastic frame  302  that covers the side and sharp edges of the anode  300 . The anode  300  is a rectangular block with a first flat surface and a second flat surface that are opposite one another. A tab  304  extends from the top of the plastic frame  302  and provides both a mechanical and electrical connection to the anode  300 . The tab  304  is monolithic with regard to the anode  300  such that the tab  304  extends through the plastic frame  302 . The tab  304  allows for the anode  300  to be pulled out of the battery in a few seconds. In one embodiment, the anode  300  is a 5000 or 6000 series aluminum with the rectangular anode bonded or glued to an injection molded PVC plastic frame  302 . 
       FIG. 4  depicts a cathode plate  400 . The cathode plate  400  has air channels  402  that allow for oxygen to enter the cathode matrix and react with the battery chemistry. The air channels  402  provide a waffle-type pattern that can be seen at the edge of the cathode  400  in  FIG. 4 . A back plate  404  to the cathode  400  is formed so the air channels  402  are open to the air. The cathode front  406  is a flat block on the front that, when attached, forms one side of the air channel  402  and is the side that feeds oxygen to the back of the cathode  400 . The cathode plate  400  may be manufactured from a carbon powder matrix mixed with a hydrophobic binder and a catalyst material along with embedded metal wire charge collectors. Other cathode materials well known to those skilled in the art can be applied to the manufacture of the cathode plate  400 . Each cathode plate  400  is made of carbon powder with a hydrophobic binder such as a polytetrafluoroethylene sold under the brand name TEFLON® that allows oxygen to permeate the surface but prevents liquid from leaking out of the battery cell chamber  500  (see  FIG. 5 ). In one embodiment, liquid TEFLON® is mixed with carbon powder at about a 20% (m/m) and allowed to dry to form a hydrophobic barrier to liquid. 
       FIG. 5  depicts a battery cell chamber  500 . The anode  300  (not shown in  FIG. 5 ) is inserted into a slot  506 . The battery cell chamber  500  has two open faces  508  wherein the cathode plate  400  (not shown in  FIG. 5 ) will be attached. The spacer  510  provides a gap between a surface of the anode  300  and a surface of the cathode plate  400  which functions as the electrolyte chamber  700  (see  FIG. 7 ).  FIG. 6  depicts the completed assembly. On the side of the battery cell chamber  500  are inlets  502  and outlets  504  for circulation of battery electrolyte with an electrolyte pump. 
       FIG. 6  illustrates the anode  300  inserted into a single battery cell chamber  500  that has cathode plates  400  ( FIG. 4 ) attached to each side of the battery cell chamber  500  and sealed so the unit is liquid tight. The plastic frame  302  has a tab  304  on the upper surface that is electrically connected to the anode  300  as well as being used for mechanical extraction of the anode  300 . When the anode  300  is pushed into the battery cell chamber  500  it forms two chambers on each side of the anode  300  with juxtaposed cathode plates  400  on each side. The anode  300  and the cathode plate  400  are parallel one another. 
     Referring to  FIG. 6 , on top of and to each side of the battery cell are mounted two air gun plenums  600 ,  602 . The air gun plenums  600 ,  602  are on opposite sides of the anode  300 . These air gun plenums  60 Q,  602  provide an even sheet of high-pressure air on shutdown of the battery for the purposes of wiping clean and drying the anode  300  such that the battery electrolyte is rapidly removed. The battery is started by moving the anode  300  down into the battery cell chamber  500  and starting the flow of electrolyte. To shut down the battery the electrolyte is drained out of the battery cell chamber  500 , the air gun plenums  600 ,  602  are simultaneously actuated and the anode  300  is pulled out past the air gun plenums  600 ,  602  so the surface is wiped clean and dry of electrolyte. 
       FIG. 7  shows the electrolyte chambers  700  formed on each side of the anode  300  after insertion of the anode  300  into the battery cell chamber  500 . The electrolyte chamber  700  is a few millimeters wide (e.g. 1-3 mm) and formed with the battery cell chamber  500  as side walls and the cathode plate  400  and anode  300  as endplates forming the electrolyte chamber that contains electrolyte. This chamber is on either side of the anode  300  that acts as a common wall for both sides. 
     The air gun plenums  600 ,  602  have a continuous gap that extends over the width of the anode  300  that generates a curtain of high flow air. This high flow air (e.g. about 7 kPa provides about air with a velocity of about 152 meters per second flow rate) impacts the surface of the anode  300  as it is retracted and pushes the film of electrolyte down off the anode  300  and back into the electrolyte chamber  700 . In one embodiment, the air flows at a velocity of at least 100 meters per second and less than 1000 meters per second. The extraction rate may be, for example, approximately 2.5 cm per second meaning that a 15.2 cm long anode  300  will allow for battery shutdown in about 6 seconds. For example, the anode may be pulled out in between 3 seconds and 10 seconds. In another embodiment, the anode may be pulled out in between 3 seconds and 6 seconds. The extraction may leave a portion (e.g. more than 1% but less than 20% of total length) of the anode  300  within the battery cell chamber  500 . In one embodiment, more than 1% but less than 10% remains within the battery cell chamber  500 . This facilitates re-insertion of the anode  300  into the battery cell chamber  500 . The advantage to the air curtain is no matter what shape the surface of the anode  300  has adopted due to galvanic corrosion the air will conform to the surface shape and clear the electrolyte from the anode  300 . With the anode  300  now clean and dry the battery can wait until power is need again. The anode  300  can be inserted into the battery in a few seconds such that the battery turned on in less time than was required to turn the battery off. It will be apparent to those skilled in the art that any number of mechanisms can be used to pull the anode  300  in and out of the battery cell chamber  500 . For example, in one embodiment, pneumatic cylinders may be used to pull the anode  300  in and out of the battery cell chamber  500 . These pneumatic cylinders can also provide air to the air gun plenums  600 ,  602 . 
     Multiple battery cell chamber can be arranged in electrical series or parallel with one another. In the embodiment of  FIG. 6 , two such battery cell chambers are stacked in a single assembly. In other embodiments, three or more battery cell chambers are stacked in a single assembly. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.