Page 231 - Handbook of Battery Materials

200 7 Bromine-Storage Materials

Table 7.1 General possibilities for bromine storage.

Chemical stabilization Examples and references

Storage in inorganic solid matrix Intercalation into graphite [6, 7]
Carbon-bromine adduct [4]
In zeolites [8]
Polymetric matrix Polydiallyldimethylammonium bromide [9]
Polypyrrole [10]
Poly (N,N-dimethyl)-3,4-pyrrolidinium bromide [11]
Styrene-divinyl benzene copolymers [4]
Polyacrylamide [12]
Ion-exchanger resins De-acidite FF anion exchange resin [13]
Charge-transfer complexes Dioxane, pyridine, polyvinyl, pyrrolidone, poly-2-vinyl
pyridine, polyethyleneoxide [4]
Further organic storing materials Phenyl bromide [14], pyridine, 1-picoline, 2,6-lutidine
[15–17]
Arsonium salts [18, 19]
Phosphonium salts [20]
Pyridinium bromides [21]
Aromatic amines [22]
Urotropin-bromine adduct [23]
Pyridinium and sulfonium salts [24]
Propionitrile [25]

development of solid-state batteries [12]. However, high self-discharge rates have
remained an unsolved problem for this cell type until today. The zinc-flow battery
using liquid polybromide phase from the reaction with quaternary ammonium
salts is currently of practical importance in the field of alternative systems of energy
storage.

7.2.2
Quaternary Ammonium-Polybromide Complexes

The tendency of the halogens to form chain-like polyanions that are stabilized
by delocalization of the negative charge [15, 34] is a basic chemical principle.
Donor–acceptor interactions between Lewis-acidic Br 2 and halide anions, but also
with polyhalides acting as Lewis bases, give rise to the formation of a variety of
homo- and heteroatomic adducts. The maximum number of atoms in these chains
increases with the atomic weights of the halogens (i.e., C1 < Br < I). Stabilities of
the predominant species, Br and Br , in aqueous [35, 36] and organic solvents
−
−
3 5
[36, 37] were studied by means of IR, Raman, and UV spectroscopy. In Br − a
3
substantial elongation of bond distances occurs compared with the Br 2 molecule
(2.55 vs 2.28 ˚ A). The asymmetric and symmetric Br–Br stretching modes at
∼201–210 and 160–170 cm −1 of dissolved tribromide ions in various solvents were
found in Raman spectroscopic studies [36] to be approximately 100 cm −1 lower