Electrode assembly and flow battery with improved electrolyte distribution

Abstract

An electrode assembly for a flow battery is disclosed comprising a porous electrode material, a frame surrounding the porous electrode material, at least a distributor tube embedded in the porous electrode material having an inlet for supplying electrolyte to the porous electrode material and at least another distributor tube embedded in the porous electrode material having an outlet for discharging electrolyte out of the porous material. The walls of the distributor tubes are preferably provided with holes or pores for allowing a uniform distribution of the electrolyte within the electrode material. The distributor tubes provide the required electrolyte flow path length within the electrode material to minimize shunt current flowing between the flow cells in the battery stack.

We claim: 
     
         1 . An electrode assembly for a flow battery comprising:
 a porous electrode material;   a frame surrounding the porous electrode material;   at least a first distributor tube embedded in the porous electrode material, the first distributor tube having an inlet for supplying electrolyte to the porous electrode material; and   at least a second distributor tube embedded in the porous electrode material, the second distributor tube having an outlet for discharging electrolyte out of the porous electrode material,   wherein the frame and the distributor tubes are made of an electrically non-conductive plastic material.   
     
     
         2 . The electrode assembly of  claim 1  wherein the first and second distributor tubes extend between a first side of the frame and a second side of the frame, beyond the midpoint between the two sides of the frame. 
     
     
         3 . The electrode assembly of  claim 1  wherein the first distributor tube has an outlet sealed to the frame and the second distributor tube has an inlet sealed to the frame and wherein the first and the second distributor tubes are hollow tubes each having an interior flow passage and a wall surrounding the interior passage, wherein the wall of the hollow tubes is made of a solid material provided with holes to allow the flow of electrolyte through the wall of the distributor tube into the porous electrode material. 
     
     
         4 . The electrode assembly of  claim 1  wherein the first distributor tube has an outlet sealed to the frame and the second distributor tube has an inlet sealed to the frame and wherein the first and the second distributor tubes are hollow tubes, each having an interior flow passage and a wall surrounding the interior passage, wherein the wall of the hollow tubes is made of a porous material to allow the flow of electrolyte through the wall of the distributor tube into the porous electrode material. 
     
     
         5 . The electrode assembly of  claim 1  wherein the first distributor tube has an outlet open to the porous electrode material and the second distributor tube has an inlet open to the porous electrode material. 
     
     
         6 . The electrode assembly of  claim 5  wherein the first distributor tube and the second distributor tube are hollow tubes, each having an interior flow passage and a wall surrounding the interior passage, wherein the wall of at least one of the hollow tubes is made of a solid material. 
     
     
         7 . The electrode assembly of  claim 5  wherein the first distributor tube and the second distributor tube are hollow tubes with an interior flow passage and a wall surrounding the interior passage, wherein the wall of at least one of the hollow tubes is made of a porous material for allowing the distribution of electrolyte within the porous electrode material. 
     
     
         8 . The electrode assembly of  claim 5  wherein the first distributor tube and the second distributor tube are hollow tubes each having an interior flow passage and a wall surrounding the interior passage, wherein the wall of each hollow tube is made of a solid material provided with at least one hole for allowing the distribution of electrolyte within the porous electrode material. 
     
     
         9 . The electrode assembly of  claims 1  wherein first and the second distributor tubes are hollow tubes each having an interior flow passage and a wall surrounding the interior passage, wherein the interior flow passages of at least one of the first or second distributor tubes is made of a porous material having a higher porosity than the porosity of the wall. 
     
     
         10 . The electrode assembly of  claim 1  wherein at least one of the first or second distributor tubes has a circular cross-section. 
     
     
         11 . The electrode assembly of  claim 1  wherein at least one of the first or second distributor tubes has a triangular cross-section. 
     
     
         12 . The electrode assembly of  claim 1  wherein at least one of the first or second distributor tubes is entirely embedded within the porous electrode material. 
     
     
         13 . The electrode assembly of  claim 1  wherein at least one of the first or second distributor tubes is partially embedded in the porous electrode material. 
     
     
         14 . The electrode assembly of  claim 1  wherein at least one of the first or second distributor tubes is a hollow tube having a serpentine shape and a wall of the hollow tube is made of a solid material provided with at least one hole for allowing the distribution of electrolyte within the porous electrode material. 
     
     
         15 . The electrode assembly of  claim 1  wherein at least one of the first or second distributor tubes is a hollow tube having a serpentine shape and a wall of the hollow tube is made of a porous material for allowing the distribution of electrolyte within the porous electrode material. 
     
     
         16 . The electrode assembly of  claim 1  comprising a plurality of first and second distributor tubes which are evenly distributed across the area of the porous electrode material. 
     
     
         17 . The electrode assembly of  claim 1  comprising a plurality of first and second distributor tubes of equal cross-sectional flow areas. 
     
     
         18 . The electrode assembly of  claim 1  wherein the length of the first distributor tube is equal to the length of the second distributor tube. 
     
     
         19 . The electrode assembly of  claim 1  wherein the first and second distributor tubes are made of polyethylene or polypropylene. 
     
     
         20 . A flow battery comprising at least one flow cell which comprises:
 a negative electrode assembly and a positive electrode assembly,   a separator separating the positive electrode assembly and the negative electrode assembly, and   a first and a second bipolar plate, each bipolar plate being adjacent to a respective electrode assembly,   wherein at least one of the negative or positive electrode assemblies is an electrode assembly of  claim 1 .   
     
     
         21 . A flow battery which comprises a stack of flow cells separated by bipolar plates, each flow cell comprising a positive electrode assembly and a negative electrode assembly separated by a separator, each electrode assembly having a porous electrode material surrounded by a frame, wherein the stack of flow cells is enclosed in a cylindrical plastic shell provided with two end plates, the stack of flow cells being connected to the inside wall of the cylindrical plastic shell and wherein the cylindrical plastic shell and the two end plates are made of an electrically non-conductive material and the cylindrical plastic shell compresses the flow cells in a radial direction and the two end plates compress the flow cells in an axial direction. 
     
     
         22 . The flow battery of  claim 21  wherein the material of the cylindrical plastic shell and of the end plates has about the same thermal expansion coefficient as the material of the frames. 
     
     
         23 . The flow battery of  claim 22  wherein the material of the frames, the cylindrical plastic shell and the end plates is polyethylene or polypropylene. 
     
     
         24 . The flow battery of  claim 21  wherein the stack of flow cells has a rectangular exterior shape with its corners connecting with the interior surface of the cylindrical plastic shell to create four compartments between the stack and the cylindrical plastic shell. 
     
     
         25 . The flow battery of  claim 24  wherein the corners of the stack are connected to the interior wall of the cylindrical plastic shell through seals to create four sealed compartments between the stack and the cylindrical plastic shell for flowing positive and negative electrolytes there through. 
     
     
         26 . A flow battery which comprises a stack of flow cells having an electrode assembly of  claim 1 , wherein the stack of flow cells is enclosed in a cylindrical plastic shell provided with two end plates, the cylindrical plastic shell and the two end plates being made of an electrically non-conductive material and holding the flow cells together and compressing them in a radial and an axial direction. 
     
     
         27 . The flow battery of  claim 26  wherein the material of the cylindrical plastic shell and of the end plates has about the same thermal expansion coefficient as the material of the frames. 
     
     
         28 . The flow battery of  claim 26  wherein the stack of flow cells has a rectangular exterior shape with its corners connecting with the interior surface of the cylindrical plastic shell to create four compartments between the stack and the cylindrical plastic shell. 
     
     
         29 . The flow battery of  claim 26  wherein the corners of the stack are connected to the interior surface of the cylindrical plastic shell through seals to create four sealed compartments between the stack and the cylindrical plastic shell, two compartments for flowing a positive electrolyte there through and two other compartments for flowing a negative electrolyte there through. 
     
     
         30 . A method of manufacturing an electrode assembly for a flow battery comprising the steps of:
 positioning a porous electrode material within a frame;   inserting locating needles through holes provided in the frame surrounding the porous electrode material and into the porous electrode material;   sliding distributor tubes through the holes provided in the frame and through holes provided in the porous electrode material by inserting the locating needles within the porous electrode material, to thereby locate the distributor tubes within the porous material and relative to the frame; and   sealing the distributor tubes within the holes of the frame.   
     
     
         31 . The method of  claim 30  further comprising sealing the ends of at least one distributor tube to prevent electrolyte flow through its inlet or outlet. 
     
     
         32 . A method of manufacturing an electrode assembly for a flow battery comprising the steps of:
 a. securing at least one distributor tube to an electrode frame;   b. positioning a porous electrode material next to the electrode frame over the distributor tube; and   c. compressing the electrode frame, the distributor tube and the porous electrode material to at least partially embed the distributor tube within the porous electrode material.   
     
     
         33 . A method of manufacturing a flow battery stack comprising the steps of:
 a. securing at least one distributor tube to an electrode frame;   b. positioning successively an electrode frame with distributor tubes, an electrode material, a separator, another electrode material, another electrode frame with distributor tubes one over the other;   c. repeating the steps a) and b) until a desired number of flow cells in the stack is reached ; and   d. compressing a stack of components formed in steps a) to c) to at least partially embed the distributor tubes within the porous electrode material.   
     
     
         34 . The method of  claim 33  further comprising sealing the ends of at least one distributor tube to prevent electrolyte flow through its inlet or outlet. 
     
     
         35 . A method of making the flow battery of  claim 21  comprising the steps of:
 a. providing the cylindrical plastic shell and the two end plates; 
 b. placing the stack of flow cells within the cylindrical plastic shell such that the flow cells are connected to the inside wall of the cylindrical plastic shell and the cylindrical plastic shell compresses the flow cells in a radial direction; and 
 c. compressing the stack of flow cells in axial direction between the two end plates.