Synthesis and characterization of composite positive electrode materials for aqueous zinc-ion batteries

The growing dependence on renewable energy sources for sustainable power generation has
highlighted the critical need for advanced grid-scale energy storage systems. Among these,
rechargeable batteries have emerged as leading candidates. However, they face significant
challenges, including high production costs and the environmental hazards associated with their
components. To address these issues, aqueous batteries have attracted considerable attention as
an alternative to their organic counterparts due to their cost-effectiveness, safety, and
environmental compatibility.
Among aqueous batteries, rechargeable aqueous zinc-ion batteries (A-ZIBs) stand out as a
particularly promising option. This is largely due to the advantageous properties of zinc, such
as its low redox potential, high theoretical capacity, low cost, non-toxicity, and abundance.
Despite these advantages, the commercialization of A-ZIBs has been largely hindered by
challenges related to their poor cycle life.
This dissertation investigates strategies to overcome the limited cycle life of A-ZIBs with a
particular focus on Copper Hexacyanoferrate (CuHCF) as a positive electrode material. The
research examines the effects of thermal treatment on the chemical composition, morphology,
and electrochemical performance of CuHCF. The findings indicate that optimized thermal
conditions significantly influence the structure of CuHCF, leading to improved cycling
stability. Additionally, after a comprehensive review of the recent relevant studies, the
application of conductive polymer coatings, including polypyrrole and poly(3,4-
ethylenedioxythiophene):polystyrene sulfonate to CuHCF is analyzed. These coatings act as
protective layers, enhancing structural integrity, delaying the phase transition in the CuHCF
lattice, and extending the cycle life. The optimal polymer concentration in the coating solutions
was further studied to maximize the outcoming electrochemical performance. The research
further explores the development of an innovative pouch cell design incorporating a
biodegradable membrane. Transitioning from conventional flooded cell designs to the more
practical pouch configurations presented challenges, particularly related to cycling stability.
However, the integration of the biodegradable membrane enabled a significantly enhanced
cycling stability and efficiency while aligning well with the environmental goals of A-ZIBs for
grid-scale energy storage.