RESUMO
The irreversibility and low utilization of Zn anode stemming from the corrosion and dendrite growth have largely limited the commercialization of aqueous zinc batteries. Here, a carbonyl-rich polymer interphase of zinc polyacrylate (ZPAA) is spontaneously in-situ constructed on Zn anode to address the above-mentioned dilemmas. The ZPAA interlayer enables fast transport kinetics of Zn2+ and tailors the interfacial electric field for realizing the uniform Zn deposition due to superior zincophilicity, high Zn2+ transference number and inherent ion-diffusion channel. Importantly, acting as a buffer interphase with strong adhesion and isolation of electrolytes, this functional layer effectively protects the Zn electrode against the water-induced erosion and passivation. Remarkably, the ZPAA@Zn electrode realizes an enhanced Coulombic efficiency of 99.71 % within 2200 cycles, delivers an ultra-long cycling stability over 7660 h (>319 days, 1 mA cm-2) and 2460 h (5 mA cm-2) with lower voltage hysteresis. Also, the ZPAA@Zn/MnO2 full cell maintains a high capacity of 114 mAh/g after 2000 cycles, much better that of untreated Zn/MnO2 cell (25 mAh/g). This concept of in-situ fabricating ion-sieve-like polymer interphase provides a facile approach to stabilize Zn anode and further paves a way for high-performance aqueous batteries.
RESUMO
The properties of polymers near an interface are altered relative to their bulk value due both to chemical interaction and geometric confinement effects. For the past two decades, the dynamics of polymers in confined geometries (thin polymer film or nanocomposites with high-surface area particles) has been studied in detail, allowing progress to be made toward understanding the origin of the dynamic effects near interfaces. Observations of mechanical property enhancements in polymer nanocomposites have been attributed to similar origins. However, the existing measurement methods of these local mechanical properties have resulted in a variety of conflicting results on the change of mechanical properties of confined polymers. Here, an atomic force microscopy (AFM)-based method is demonstrated that directly measures the mechanical properties of polymers adjacent to a substrate with nanometer resolution. This method allows us to consistently observe the gradient in mechanical properties away from a substrate in various materials systems, and paves the way for a unified understanding of thermodynamic and mechanical response of polymers. This gradient is both longer (up to 170 nm) and of higher magnitude (50% increase) than expected from prior results. Through the use of this technique, we will be better able to understand how to design polymer nanocomposites and polymeric structures at the smallest length scale, which affects the fields of structures, electronics, and healthcare.