Sealed aqueous flow battery systems with in-tank electrolyte rebalancing

Abstract

A battery system comprising a sealed aqueous flow battery that employs a passive, in-tank electrolyte recombination system. The recombination system allows for electrolyte stabilization in batteries where hydrogen evolution may occur as a side reaction without the need to use any externally-supplied rebalancing reactants. The system is a passive system that does not require a control system, additional pumps, or pumping energy.

1 . A sealed aqueous flow battery system comprising:
 an electrolyte system including a negative electrolyte reservoir containing a negative electrolyte and a positive electrolyte reservoir containing a positive electrolyte;   a charge/discharge reaction cell having a separator disposed within a reaction chamber and independent fluid connections on opposing sides of the separator to receive negative electrolyte from the negative electrolyte reservoir and positive electrolyte from the reservoirs; and   an oxidation reactor positioned at least partially in contact with fluids contained in the positive electrolyte reservoir, wherein the oxidation reactor receives hydrogen gas generated by the charge/discharge reaction of the battery system and supplies protons to the battery system.   
     
     
         2 . A flow battery system according to  claim 1 , wherein a plurality of oxidation reactors are included. 
     
     
         3 . A flow battery system according to  claim 1 , wherein the oxidation reactor is one of a capillary-action galvanic reactor and a membrane electrode assembly. 
     
     
         4 . A flow battery system according to  claim 1 , wherein the oxidation reactor includes a plurality of membrane electrode assemblies. 
     
     
         5 . A flow battery system according to  claim 1 , wherein the oxidation reactor is in fluidic contact with: a) hydrogen gas provided to a head space of the positive electrolyte reservoir, and b) the positive electrolyte. 
     
     
         6 . A flow battery system according to  claim 1 , wherein the oxidation reactor comprises a porous material. 
     
     
         7 . A flow battery system according to  claim 1 , wherein the oxidation reactor is at least one of: free-floating on the positive electrolyte and partially submerged in the positive electrolyte. 
     
     
         8 . A flow battery system according to  claim 1 , wherein the oxidation reactor comprises a hydrogen electrode and an iron electrode. 
     
     
         9 . A flow battery system according to  claim 6 , wherein catalyst is carried on a single end of the porous electrode. 
     
     
         10 . A flow battery system according to  claim 9 , wherein the oxidation reactor comprises a catalyst including at least one of platinum, palladium, iridium, and ruthenium. 
     
     
         11 . A flow battery system according to  claim 1 , wherein the oxidation reactor comprises a carbon material exposed to a solution phase reaction of metal ions in the positive electrolyte. 
     
     
         12 . A flow battery system according to  claim 1 , wherein a head space of the positive electrolyte reservoir is connected via a hydrogen gas conduit to receive hydrogen gas provided from a head space over the negative electrolyte reservoir. 
     
     
         13 . A flow battery system according to  claim 12 , wherein the hydrogen gas conduit includes an air mover. 
     
     
         14 . A flow battery system according to  claim 1 , wherein the electrolyte system also includes at least one electrolyte pump associated with the fluid connection between the reaction cell and at least one of the negative electrolyte reservoir and the positive electrolyte reservoir. 
     
     
         15 . A flow battery system according to  claim 1 , further comprising an in-line proton diffusion cell. 
     
     
         16 . A flow battery system according to  claim 1 , wherein the reaction cell includes at least one of a graphite plate and a carbon felt material. 
     
     
         17 . A flow battery system according to  claim 1 , wherein the battery system is selected from a vanadium flow battery, an iron flow battery, an iron-chromium battery, and a zinc-bromine battery. 
     
     
         18 . A flow battery system according to  claim 1 , wherein protons react with the positive electrolyte in the positive electrolyte reservoir to produce ferrous ions. 
     
     
         19 . A flow battery system according to  claim 1 , wherein the battery system is passive. 
     
     
         20 . A flow battery system according to  claim 19 , wherein the passive battery system is characterized by an absence of pumps and pressurized gases. 
     
     
         21 . A flow battery system according to  claim 19 , wherein the passive battery system is characterized by an absence of externally-supplied rebalancing reactants. 
     
     
         22 . A method of rebalancing reactants in a sealed aqueous flow battery system comprising a negative electrolyte reservoir, a positive electrolyte reservoir including an oxidation reactor, and a charge/discharge reaction cell, the method comprising:
 providing negative electrolyte and positive electrolyte to the reaction cell to drive a charge/discharge reaction;   transporting hydrogen gas evolved from the charge/discharge reaction to the positive electrolyte reservoir;   converting at least a portion of the hydrogen gas into protons in the oxidation reactor;   acidifying the positive electrolyte proximate to oxidation reactor with the protons supplied by the oxidation reactor; and   returning the acidified positive electrolyte to the reaction cell.   
     
     
         23 . The method according to  claim 22 , further comprising supplying the acidified positive electrolyte to a diffusion cell before returning the acidified positive electrolyte to the reaction cell. 
     
     
         24 . The method according to  claim 22 , further comprising providing a head space within the negative and positive electrolyte reservoirs and wherein the hydrogen gas is transported through both the negative and positive electrolyte head spaces before the hydrogen gas is converted to protons.