9
away, thus less research attention has accumulated on aqueous separators.
Manufacturer’s cost appetite for separators in aqueous systems is less than in other
battery categories due to overall system cost being lower, but the choice of separator
has profound effect on cycle life of Zn battery systems due to protection from zinc
dendrites that may short-circuit, and also due to protection from zinc electrode
shape change. To prevent short-circuits a nano-pore cellophane membrane is found
in almost all zinc-alkaline battery systems, including some single-use cells. Celgard
or similar polymer layers with sub-micron pore size are sometimes substituted for
the cellophane but cost often limits this substitution.
In addition to the cellophane layer, a water-absorbent fleece layer (a.k.a. nonwoven felt) is also commonly placed next to the zinc electrode to prevent drying
out. Pellon is a proprietary version of this water-absorbent layer and is used when
chemical stability of the separator is an issue. Several variants of Pellon are offered
commercially. An approximate listing of the various wicking layers for alkaline
systems using a zinc anode is given in Arora and Zhang [40].
3 Next-Generation Materials for Mn-Zn and Ni-Zn Systems
3.1 Advanced Rechargeable Manganese Cathodes
MnO 2 chemistries that cycle ~2 electrons per Mn were recently published for both
alkaline and acidic electrolytes [14, 15, 23, 41]. Pan et al. [23] reported long cycle
life of ~285 mAh/g from a cathode of α-MnO 2 pressed with carbon powder and
Fig. 6 A commercial Ni-Zn battery product from Evercel corporation, circa 2001. The pasteNiOOH (left) and paste-ZnO (right) electrodes used in this technology are shown to the right side
of the battery
Aqueous Mn-Zn and Ni-Zn Batteries for Sustainable Energy Storage
away, thus less research attention has accumulated on aqueous separators.
Manufacturer’s cost appetite for separators in aqueous systems is less than in other
battery categories due to overall system cost being lower, but the choice of separator
has profound effect on cycle life of Zn battery systems due to protection from zinc
dendrites that may short-circuit, and also due to protection from zinc electrode
shape change. To prevent short-circuits a nano-pore cellophane membrane is found
in almost all zinc-alkaline battery systems, including some single-use cells. Celgard
or similar polymer layers with sub-micron pore size are sometimes substituted for
the cellophane but cost often limits this substitution.
In addition to the cellophane layer, a water-absorbent fleece layer (a.k.a. nonwoven felt) is also commonly placed next to the zinc electrode to prevent drying
out. Pellon is a proprietary version of this water-absorbent layer and is used when
chemical stability of the separator is an issue. Several variants of Pellon are offered
commercially. An approximate listing of the various wicking layers for alkaline
systems using a zinc anode is given in Arora and Zhang [40].
3 Next-Generation Materials for Mn-Zn and Ni-Zn Systems
3.1 Advanced Rechargeable Manganese Cathodes
MnO 2 chemistries that cycle ~2 electrons per Mn were recently published for both
alkaline and acidic electrolytes [14, 15, 23, 41]. Pan et al. [23] reported long cycle
life of ~285 mAh/g from a cathode of α-MnO 2 pressed with carbon powder and
Fig. 6 A commercial Ni-Zn battery product from Evercel corporation, circa 2001. The pasteNiOOH (left) and paste-ZnO (right) electrodes used in this technology are shown to the right side
of the battery
Aqueous Mn-Zn and Ni-Zn Batteries for Sustainable Energy Storage