Enhancing Water Absorption in Sulfonated Poly(arylene ether sulfone) Polymer Electrolyte Membranes by Reducing Chain Entanglement through Constrained Deswelling

The water uptake of a polymer electrolyte membrane is a critical parameter that determines the dimensional stability and transport behavior in various energy conversion devices. In this study, the water uptake of a sulfonated poly(arylene ether sulfone) (SPAES) membrane was controlled solely by the number of chain entanglements without employing any water absorbents. Through the constrained deswelling process, the SPAES membrane achieved a significant enhancement in water uptake, increasing by up to 210% at room temperature. This notable improvement in water uptake originates from the reduction in elastic friction, represented by the number of chain entanglements, against the volume expansion resulting from the absorption of water by the sulfuric acid groups. Evidently, the controlled deswelling procedure led to biaxial stretching of the SPAES membrane, causing an increase in its surface area and a decrease in thickness. At the microscopic level, this controlled deswelling process might prompt the alignment of hydrophilic channels along the plane directions. These changes brought about by the controlled deswelling process resulted in changes to the membrane’s tensile characteristics and its transport behavior for protons and hydrogen gas

Conducting Polymer-Skinned Electroactive Materials of Lithium-Ion Batteries: Ready for Monocomponent Electrodes without Additional Binders and Conductive Agents

Rapid growth of mobile and even wearable electronics is in pursuit of high-energy-density lithium-ion batteries. One simple and facile way to achieve this goal is the elimination of nonelectroactive components of electrodes such as binders and conductive agents. Here, we present a new concept of monocomponent electrodes comprising solely electroactive materials that are wrapped with an insignificant amount (less than 0.4 wt %) of conducting polymer (PEDOT:PSS or poly­(3,4-ethylenedioxythiophene) doped with poly­(styrenesulfonate)). The PEDOT:PSS as an ultraskinny surface layer on electroactive materials (LiCoO₂ (LCO) powders are chosen as a model system to explore feasibility of this new concept) successfully acts as a kind of binder as well as mixed (both electrically and ionically) conductive film, playing a key role in enabling the monocomponent electrode. The electric conductivity of the monocomponent LCO cathode is controlled by simply varying the PSS content and also the structural conformation (benzoid-favoring coil structure and quinoid-favoring linear or extended coil structure) of PEDOT in the PEDOT:PSS skin. Notably, a substantial increase in the mass-loading density of the LCO cathode is realized with the PEDOT:PSS skin without sacrificing electronic/ionic transport pathways. We envisage that the PEDOT:PSS-skinned electrode strategy opens a scalable and versatile route for making practically meaningful binder-/conductive agent-free (monocomponent) electrodes

Inverse Opal-Inspired, Nanoscaffold Battery Separators: A New Membrane Opportunity for High-Performance Energy Storage Systems

The facilitation of ion/electron transport, along with ever-increasing demand for high-energy density, is a key to boosting the development of energy storage systems such as lithium-ion batteries. Among major battery components, separator membranes have not been the center of attention compared to other electrochemically active materials, despite their important roles in allowing ionic flow and preventing electrical contact between electrodes. Here, we present a new class of battery separator based on inverse opal-inspired, seamless nanoscaffold structure (“IO separator”), as an unprecedented membrane opportunity to enable remarkable advances in cell performance far beyond those accessible with conventional battery separators. The IO separator is easily fabricated through one-pot, evaporation-induced self-assembly of colloidal silica nanoparticles in the presence of ultraviolet (UV)-curable triacrylate monomer inside a nonwoven substrate, followed by UV-cross-linking and selective removal of the silica nanoparticle superlattices. The precisely ordered/well-reticulated nanoporous structure of IO separator allows significant improvement in ion transfer toward electrodes. The IO separator-driven facilitation of the ion transport phenomena is expected to play a critical role in the realization of high-performance batteries (in particular, under harsh conditions such as high-mass-loading electrodes, fast charging/discharging, and highly polar liquid electrolyte). Moreover, the IO separator enables the movement of the Ragone plot curves to a more desirable position representing high-energy/high-power density, without tailoring other battery materials and configurations. This study provides a new perspective on battery separators: a paradigm shift from plain porous films to pseudoelectrochemically active nanomembranes that can influence the charge/discharge reaction