Researchers from South Korea’s Gwangju Institute of Science and Technology (GIST) have developed a nitrogen-doped mesoporous carbon-coated graphite felt (NMC/GF) electrode that could make flowless zinc-bromine batteries (FLZBB) a potential alternative to the ubiquitous, albeit flawed, lithium-ion batteries.
Typically, the non-flammable electrolytes in a FLZBB offer safety but it suffers from self-discharge due to the crossover of active materials. The use of an NMC/GF electrode is a low cost, evaporation-induced self-assembly method that helps to prevent this self-discharge.
In the GIST method, the graphite felt was coated with precursor materials and mixed in a solvent. After drying and curing, when applied to an FLZBB, the electrodes suppressed the crossover of the active materials and prevented self-discharge. This was due to the mesopores present on the GF fibers, GIST said.
“The NMC coating on the GF electrodes introduced mesopores with strategically embedded nitrogen sites, which served as a stronghold, capturing the bromine and bromine complexes in the positive electrode, suppressing bromine crossover and self-discharge phenomena,” said Chanho Pak, professors at GIST and leader of the research. “Moreover, this coating made the originally hydrophobic pristine GF electrodes ultrahydrophilic, improving interfacial contact with the electrolyte in the aqueous electrolyte and enhancing electrochemical performance. Additionally, it allowed the incorporation of abundant oxygen and nitrogen species, which improved bromine reaction speeds, further boosting performance.”
During testing, the FLZBB with NMC/GF electrodes demonstrated coulombic and energy efficiencies of 96% and 76%, respectively, at a current density of 20 mA cm-2. It also had a high-rate areal capacity of 2 mAh cm-2. GIST said the battery potentially could have charge/discharge cycling stability extend to more than 10,000 cycles.
Why it matters
While lithium-ion batteries have become universal in portable devices and electric vehicles, continued problems with these batteries with flammable electrolytes and geopolitical issues with the mining of lithium have companies and universities striving to find alternatives that match the performance and power density of these batteries.
“The development of FLZBB positive electrode, which maintains long-term operation over 10,000 cycles with high efficiencies, will accelerate the development of stable energy storage systems (ESSs) and eco-friendly energy conversion in the long term,” Pak said. “Moreover, NMC/GF positive electrode can also be used for other aqueous batteries.”
The full research can be found in the journal ScienceDirect.
