Hydrogen gas relief valve

DETAILED DESCRIPTION Electrochemical devices or systems of the type referred to herein include one or more of the metal-halogen battery systems, such as a zinc-chloride battery system.
These metal-halogen battery systems generally are comprised of three basic components, namely an electrode stack section, an electrolyte circulation subsystem, and a store subsystem.
The electrode stack station typically includes a plurality of cells connected together electrically in various series and parallel combinations to achieve a desired operating voltage and current at the battery terminals over a charge/discharge battery cycle.
Each cell is comprised of a positive and negative electrode which are both in contact with an aqueous metalhalide electrolyte.
The electrolyte circulation subsystem operates to circulate the metalhalide electrolyte from a reservoir through each of the cells in the electrode stack in order to replenish the metal and halogen electrolyte ionic components as they are oxidized or reduced in the cells during the battery cycle.
In a closed, self-contained metal-halogen battery system, the storage subsystem is used to contain the halogen gas or liquid which is liberated from the cells during the charging of the battery system for subsequent return to the cells during the discharging of the battery system.
In the zinc-chloride battery system, chlorine gas is liberated from the positive electrodes of the cells and stored in the form of chlorine hydrate.
Chlorine hydrate is a solid which is formed by the store subsystem in a process analogous to the process of freezing water where chlorine is included in the ice crystal.
With reference to the general operation of a zinc-chloride battery system, an electrolyte pump operates to circulate the aqueous zinc-chloride electrolyte from a reservoir to each of the positive or "chlorine" electrodes in the electrode stack.
These chlorine electrodes are typically made of porous graphite, and the electrolyte passes through the pores of the chlorine electrodes into a space between the chlorine electrodes and the opposing negative or "zinc" electrodes