Vanadium flow battery - Terminology
1 Scope
This standard specifies the terms and definitions of the vanadium flow battery.
This standard is applicable to all kinds of vanadium flow batteries.
2 Terms and definitions
2.1
vanadium flow battery; VFB
a rechargeable battery employs electrochemical reactions of vanadium ions in different valence states which exists in positive and negative electrolytes for converting electric energy and chemical energy into one another
Note: The VFB consists of mainly a power unit (stack or module), an energy unit (electrolyte and tank), an electrolyte providing unit (piping, valves, pumps, heat exchangers, etc.) and a battery management system.
2.2
ion conductive membrane
a component of a cell that separates positive and negative electrolyte, and conducts ions selectively
2.3
electrolyte
an ionic conductive fluid containing ions in different valence states of vanadium
2.4
bipolar plate
a conductive plate which separates individual cells in a stack and acts as current collector and separator of the positive and negative electrolyte
2.5
collector
a conductive plate connected to an external circuit for the input or output current
2.6
electrode
an electrical conductor in which electrochemical reactions occur
2.7
end plate
a component located on either end of the stack in the direction of the current flow for creating the required tightness to the stacked cells
2.8
cell reaction
the overall reaction between the positive electrode and the negative electrode within a cell
2.9
open circuit voltage
voltage without net flow of current in the external circuit
2.10
charge
a process of the battery for receiving electrical energy from an external circuit and for converting it into chemical energy
2.11
discharge
a process of the battery that converts chemical energy into electrical energy and outputs electrical energy to the external circuit
2.12
electrode area
geometric area of an electrode where electrochemical reactions occur
2.13
active area
geometric area of the electrode perpendicular to the direction of the current flow
2.14
current density
current per unit active area
Note: The current density is expressed as A/m2 or mA/cm2.
2.15
average charging voltage
the average of the voltage during the process of battery charging
2.16
average discharging voltage
the average of the voltage during the process of battery discharging
