Aqueous lithium air batteries

Abstract

Aqueous Li/Air secondary battery cells are configurable to achieve high energy density and prolonged cycle life. The cells include a protected a lithium metal or alloy anode and an aqueous catholyte in a cathode compartment. The aqueous catholyte comprises an evaporative-loss resistant and/or polyprotic active compound or active agent that partakes in the discharge reaction and effectuates cathode capacity for discharge in the acidic region. This leads to improved performance including one or more of increased specific energy, improved stability on open circuit, and prolonged cycle life, as well as various methods, including a method of operating an aqueous Li/Air cell to simultaneously achieve improved energy density and prolonged cycle life.

1 . An alkali metal/oxygen electrochemical energy storage cell, the cell comprising:
 an anode comprising an alkali metal electroactive component material;   an open-to-ambient-air cathode on or at which molecular oxygen obtained from the ambient air is electro-reduced during cell discharge, the cathode in alkali metal ion communication with the anode;   an aqueous catholyte comprising water and one or more organic polyprotic active compounds dissolved in water that partake in a cell discharge reaction and effectuate cathode capacity for discharge below pH 7, the catholyte in contact with said cathode, wherein the one or more organic polyprotic active compounds comprises an organic polyprotic acid that dissociates over the course of discharge, thus yielding two or more active protons per acid molecule in the catholyte that partake in the cell reaction as the discharge proceeds; and   a protective membrane architecture interposed between the cathode and the anode, the protective membrane architecture having a first and a second major surface, the first surface adjacent to the cathode and in contact with the catholyte and the second surface adjacent to the anode; and   wherein the protective membrane architecture solely allows through transport of the alkali metal ion and prevents liquids from contacting the alkali metal anode; and   wherein the organic polyprotic acid comprises a species that dissociates over the course of discharge yielding two or more active protons per acid molecule in the catholyte that partake in the cell reaction as the discharge proceeds.   
     
     
         2 . The cell of  claim 1 , wherein the catholyte comprises:
 water; and   the organic polyprotic acid is a carboxylic acid dissolved in water, the acid represented by the following general formula   
       
         
           
           
               
               
           
         
         wherein R 1  represents an organic radical; 
         wherein R 2  represents H or an organic radical; and 
         wherein R 3  represents H or an organic radical. 
       
     
     
         3 . (canceled) 
     
     
         4 . The cell of  claim 2 , wherein the carboxylic acid is malonic acid, thus R 2  and R 3  represent H and R 1  represents a carboxyl group. 
     
     
         5 . The cell of  claim 2 , wherein at least one of R 1 , R 2  and R 3  represents an organic radical selected from the group consisting of an optionally substituted C 1 -C 10  alkyl group, optionally substituted C 2 -C 10  alkenyl group, optionally substituted C 2 -C 10  alkynyl group. 
     
     
         6 . The cell of  claim 2 , wherein at least one of R 1 , R 2  and R 3  represents an organic radical selected from the group consisting of an optionally substituted C 4 -C 10  cycloalkyl, optionally substituted C 4 -C 10  cycloalkenyl, and optionally substituted 3-10 membered heterocyclyl. 
     
     
         7 . The cell of  claim 2 , wherein at least one of R 1 , R 2  and R 3  represent an organic radical selected from the group consisting of an optionally substituted carbo- and heterocyclic 5-10 membered aryl. 
     
     
         8 . The cell of  claim 2 , wherein the carboxylic acid is selected from the group consisting of malonic acid, glutaric acid, and methylsuccinic acid. 
     
     
         9 . The cell of  claim 1 , wherein the equivalent weight of the acid that partakes in the cell discharge reaction, is selected from the range of values consisting of 50-70 g/equivalent of H + ; 71-90 g/equivalent of H + ; 91-110 g/equivalent of H + . 
     
     
         10 - 12 . (canceled) 
     
     
         13 . The cell of  claim 1 , wherein the concentration of the carboxylic acid in the catholyte is between 0.05 molar and 1 molar. 
     
     
         14 . The cell of  claim 1 , wherein the catholyte further comprises solid phase carboxylic acid in contact with its solution. 
     
     
         15 . The cell of  claim 1 , wherein the catholyte is saturated with the carboxylic acid. 
     
     
         16 . The cell of  claim 1 , wherein the alkali metal electroactive component material comprises lithium. 
     
     
         17 . The cell of  claim 1 , wherein the anode is selected from the group consisting of lithium metal, lithium metal alloy, and lithium intercalation material. 
     
     
         18 . The cell of  claim 1 , wherein the anode is a lithium metal sheet. 
     
     
         19 - 120 . (canceled)