US 9,660,311 B2  29  30  vii) 2 molar citric acid and 2 molar lithium nitrate;  viii) 2 molar lithium dihydrogen citrate and 2 molar  lithium nitrate;  ix) 1 molar lithium dihydrogen citrate and 1 molar lithium  nitrate;  x) 2 molar imidazolium dihydrogen citrate and 2 or 1  molar lithium nitrate;  xi) 2 molar imidazolium hydrogen citrate and 2 or 1 molar  lithium nitrate;  xii) 2.5 molar magnesium nitrate, 0.5 molar zinc nitrate  and 1 molar lithium nitrate (pH about 3.1);  xiii) 2.8 molar magnesium nitrate, 0.2 molar zinc nitrate,  and 1 molar lithium nitrate (pH about 3.5);  xiv) 2.95 molar magnesium nitrate and 0.05 molar zinc  nitrate and 1 molar lithium nitrate (pH about 3.8).  Other Cell Components  With reference to FIG.  lA,  the cell comprises a Li anode  1.  The anode may be an alkali metal, alloy or intercalation  material, for example Li metal or a Li metal alloy or Li  intercalation material (e.g.,  lithiated carbon).  In one  example, a Li metal foil may be used. Lithium anodes,  including intercalation anodes and lithium alloys and  lithium metal anodes are well known in the lithium battery  art. In preferred embodiments the anode is lithium metal  ( e.g., in foil or sintered form) and of sufficient thickness (i.e.,  capacity) to enable the cell to achieve the rated discharge  capacity of the cell. The anode may take on any suitable  form or construct including a green or sintered compact  (such as a wafer or pellet), a sheet, film, or foil, and the  anode may be porous or dense. Without limitation, the  lithium anode may have a current collector ( e.g., copper foil,  or suitable expandable metal) pressed or otherwise attached  to it in order to enhance the passage of electrons between it  and the leads of the cell. Without limitation the cell may be  anode or cathode limited. When anode limited, the complete  discharge (corresponding to rated capacity) will substan› tially exhaust all the lithium in the anode. When cathode  limited, some active lithium will remain subsequent to the  cell delivering its rated capacity.  The anode is protected with a protective membrane archi› tecture chemically stable to both the anode and the envi› ronment of an adjacent cathode compartment  (4).  The pro› tective membrane architecture typically comprises a solid  electrolyte protective membrane  2  and an interlayer  3.  The  solid electrolyte protective membrane is sometimes referred  to herein as an ion membrane or a liquid impermeable alkali  metal ion conductive solid electrolyte barrier layer. The  protective membrane architecture is in ionic continuity with  the Li anode  1  and is configured to selectively transport Li  ions into and out of the cathode compartment  4  while  providing an impervious barrier to the environment external  to the anode. Protective membrane architectures suitable for  use in the present invention are described in applicants’  co-pending published US Applications US 2004/0197641  and US 2005/0175894 and their corresponding International  Patent Applications WO 2005/038953 and WO 2005/  083829, respectively, incorporated by reference herein.  With reference to FIG.  1B,  there is illustrated (in cross› section (left) and perspective (right)) an embodiment of a  lithium air battery cell  10  in accordance with the instant  invention. The cell is disposed in a case  11  (  e.g., a metal or  polymeric case, including but limited to a heat sealable  multilayer laminate used for that purpose). The case com› prises one or more ports  12  for the passage of oxygen and  moisture from the ambient air. To effectively reach the  Referring to FIG.  2B,  the protective membrane architec› ture can be a composite solid electrolyte  210  composed of  discrete layers, whereby the first material layer  212  (also  sometimes referred to herein as "interlayer") is stable to the  alkali metal anode  201  and the second material layer  214  is  More commonly, the ion membrane architecture is a  composite composed of at least two components of different  materials having different chemical compatibility require› ments, one chemically compatible with the anode, the other  chemically compatible with the exterior; generally ambient  air or water, and/or battery electrolytes/catholytes. By  "chemical compatibility" ( or "chemically compatible") it is  meant that the referenced material does not react to form a  product that is deleterious to battery cell operation when  contacted with one or more other referenced battery cell  components or manufacturing, handling, storage or external  environmental conditions. The properties of different ionic  conductors are combined in a composite material that has  the desired properties of high overall ionic conductivity and  chemical stability towards the anode, the cathode and ambi› ent conditions encountered in battery manufacturing. The  composite is capable of protecting an alkali metal anode  from deleterious reaction with other battery components or  ambient conditions while providing a high level of ionic  conductivity to facilitate manufacture and/or enhance per› formance of a battery cell in which the composite is incor› porated.  Referring to FIG.  2A,  the protective membrane architec› ture can be a monolithic solid electrolyte  202  that provides  ionic transport and is chemically stable to both the alkali  metal anode  201  and the external environment. Examples of  such materials are Na-W’ alumina, LiHfPO$_{4 }$ and NASICON,  Nasiglass, Li$_{5}$La$_{3 }$Ta$_{2}$O$_{12 }$ and Li$_{5}$La$_{3}$Nb$_{2}$O$_{12}$. Na$_{5}$MSi$_{4}$ O$_{12 }$ (M: rare earth such as Nd, Dy, Gd).  FIGS.  2A-D  illustrate representative protective mem› brane architectures from these disclosures suitable for use in  the present invention. The protective membrane architec› tures provide a barrier to isolate a Li anode from ambient  and/or the cathode side of the cell while allowing for  efficient ion Li metal ion transport into and out of the anode.  The architecture may take on several forms. Generally it  comprises a solid electrolyte layer that is substantially  impervious, ionically conductive and chemically compatible  with the external ambient (e.g., air or water) or the cathode  environment.  The case may further comprise an additional port (not  shown) for introducing, water or catholyte into the cathode  compartment after the cell has been manufactured. Without  limitation, the catholyte ( or water) may be introduced, prior  or subsequent to one or more of the following: cell activation  or initial discharge. For instance, the cell may be used in a  Li/ Air, or more specifically, a Li/O$_{2 }$ flow battery, wherein the  catholyte is caused to flow into, and generally through, the  cathode compartment. In accordance with such embodi- ments the battery may contain appropriate pipeworks and  pumps for circulating the catholyte may be stored external  from the cell in, e.g., a suitable storage container.  In many, but not necessarily all embodiments, the cell is  activated by removing a barrier material (not shown) which  covers the ports to prevent, prior to cell activation, prema› ture or excessive exposure of the cathode compartment to  ambient air. The cell activated by removing the barrier  material ( e.g., by the act of peeling off a tab (barrier material  layer).  cathode and the cathode compartment, as illustrated in FIG.  1B,  the case side wall of which contains the ports is adjacent  to the cathode. 