Enabling Low-Temperature Zinc-Bromine Microbatteries with an Additive-Free Electrolyte Design

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc-bromine microbatteries (Zn-Br2 MBs) offer potential for miniaturized electronics.
• Low-temperature performance is limited by antifreeze and complexing agent incompatibility, hindering polybromide dissolution inhibition.

Purpose of the Study:

• To develop an additive-free electrolyte for aqueous Zn-Br2 MBs to overcome low-temperature performance challenges.
• To investigate an electrochemically active electrolyte that inhibits polybromide dissolution without traditional complexing agents.

Main Methods:

• Formulation of an additive-free 7.5 m zinc bromide electrolyte.
• Cryogenic testing of the electrolyte and Zn-Br2 MBs at temperatures down to -60 °C.
• Electrochemical cycling stability tests and theoretical calculations.

Main Results:

• The additive-free electrolyte exhibited a freezing point of -105 °C.
• Zn-Br2 MBs demonstrated over 10,000 cycles (99% retention) at 25 °C and >2000 cycles (98% retention) at -60 °C.
• Experimental and theoretical data confirmed that low temperatures inhibit polybromide dissolution.

Conclusions:

• The proposed additive-free electrolyte design effectively addresses the incompatibility issue in Zn-Br2 MBs.
• This approach challenges the conventional use of organic complexing agents for polybromide dissolution control.
• The developed electrolyte enables robust Zn-Br2 MB performance in extreme low-temperature environments.