Redox Flow Battery Glossary

• GF = Graphite Felt
• Anolyte : gives up $e⁻$
• Catholyte : accepts $e⁻$
• Membrane : lets $p⁺$ through
• An aqueous solution of dissolved ${\text{ZnBr}}_2$ 1-4 M) is used as the electrolyte in most ZBRBs
• Bromine smells like bleach, and $B{r}_3⁻$ or polyhalide ions are highly oxidising
• Bromine shuttle effect : diffusion of polybromide ions (resulting from ${\text{Br}}_2$ binding with $\text{Br}⁻$) from cathode to anode, leading to battery degradation (self discharge, capacity fade)
• State of Charge (SoC) : higher SoC increases overpotentials of the battery
• Galvanostatic charge-discharge (GCD) -> “consistent GCD over 500 cycles” means the flow cell was repeatedly charged and discharged at a constant current/current density, and its voltage/time curves stayed stable over 500 cycles.
• Area specific resistance (ASR) : Ohmic area-specific resistance in $\mathrm{\Omega }\text{cm}²$
• H form of a cation-exchange resin : protonated acid form, as it contains fixed anionic groups, commonly sulfonate groups: $\mathrm{R}-{\mathrm{SO}}_3^{-}$ that must be balanced by $H⁺$. It contrasts with NA/K/Zn form that may cause swelling and affect conductivity
• Ionic Liquids (IL) -> Low-temperature molten salts consisting of a large organic cation and inorganic or organic anion with a melting point less than 100°C, used as BCAs in ZBFBs . Characterised by nonvolatility, nonflammability, a wide liquid range and excellent chemical and thermal stability, the unique characteristics of ILs make them proper alternatives to classical organic solvents.

Compounds

• Tetrabutylammonium bromide (TBAB)

[Br-].CCCC[N+](CCCC)(CCCC)CCCC