2 research outputs found
Zwitterionic Polymer Gradient Interphases for Reversible Zinc Electrochemistry in Aqueous Alkaline Electrolytes
Aqueous alkaline zinc batteries are of scientific and
technological
interest because of the potential they offer for cost-effective and
safe storage of electrical energy. Poor electrochemical reversibility
and shape change of the Zn anode, propensity of Zn to become passivated
by surface oxides and hydroxide films upon prolonged exposure to the
electrolyte, and electroreduction of water are well-studied but remain
unsolved challenges. Here, we create and study electrochemical and
transport properties of precise, spatially tunable zwitterionic polymer
interphases grown directly on Zn using an initiated-chemical vapor
deposition polymerization methodology. In aqueous alkaline media,
spatial gradients in compositionfrom the polymer–electrolyte
interface to the solid–polymer interfacepromote highly
reversible redox reactions at high current density (20 mA cm–2) and high areal capacity (10 mAh cm–2). Via molecular dynamics and experimental analyses, we conclude
that the interphases function by regulating the distribution and activity
of interfacial water molecules, which simultaneously enables fast
ion transport and suppression of surface passivation and the hydrogen
evolution reaction. To illustrate the practical relevance of our findings,
we study aqueous Zn||NiOOH and Zn||air batteries and observe that
zwitterionic polymer interphases produce extended life at high currents
and high areal capacity
Adaptive Ion Channels Formed in Ultrathin and Semicrystalline Polymer Interphases for Stable Aqueous Batteries
Aqueous
Zn batteries have recently emerged as promising candidates
for large-scale energy storage, driven by the need for a safe and
cost-effective technology with sufficient energy density and readily
accessible electrode materials. However, the energy density and cycle
life of Zn batteries have been limited by inherent chemical, morphological,
and mechanical instabilities at the electrode–electrolyte interface
where uncontrolled reactions occur. To suppress the uncontrolled reactions,
we designed a crystalline polymer interphase for both electrodes,
which simultaneously promotes electrode reversibility via fast and
selective Zn transport through the adaptive formation of ion channels.
The interphase comprises an ultrathin layer of crystalline poly(1H,1H,2H,2H-perfluorodecyl acrylate), synthesized and applied as a conformal
coating in a single step using initiated chemical vapor deposition
(iCVD). Crystallinity is optimized to improve interphase stability
and Zn-ion transport. The optimized interphase enables a cycle life
of 9500 for Zn symmetric cells and over 11,000 for Zn-MnO2 full-cell batteries. We further demonstrate the generalizability
of this interphase design using Cu and Li as examples, improving their
stability and achieving reversible cycling in both. The iCVD method
and molecular design unlock the potential of highly reversible and
cost-effective aqueous batteries using earth-abundant Zn anode materials,
pointing to grid-scale energy storage