Transferring Electrochemically Active Nanomaterials into a Flexible Membrane Electrode via Slow Phase Separation Method Induced by Water Vapor

Abstract

A nickel hydroxide flexible membrane electrode (Ni(OH) 2 -FME) is prepared by coagulation bath (water) directly induced phase inversion (WIPS-FME), and watervapor-induced phase inversion (VIPS-FME) methods, separately. Interestingly, a symmetrical structure of section morphology, surface porosity, and electrolyte-affinity characteristics of the flexible membrane are obtained by VIPS technology. The effects of relative humidity, exposure time, and temperatures of the phase inversion environment on the electrochemical performance and structure of VIPS are investigated. The specific capacitance of VIPS-FME reaches 2154.29 F g −1 at a current density of 1 A g −1 , which is better than WIPS-FME (1801.14 F g −1 ). Furthermore, a hybrid supercapacitor made by employing the VIPS-FME as the positive electrode and the active carbon flexible membrane (AC-FME) as the negative electrode exhibits a high specific capacitance of 96.03 F g −1 at 1 A g −1 , a maximum energy density of 30.01 W h kg −1 , and maximum power density of 3750.95 W kg −1 with the energy density of 16.4 W h kg −1 .

Fabrication of a Cation Exchange Membrane with Largely Reduced Anion Permeability for Advanced Aqueous K‐ion Battery in an Alkaline‐Neutral Electrolyte Decoupling System

“…While, when the proportion of PES increases to 60%, the system is down (break circuit) owing to the poor ion exchange function of the membrane (see Figure S12g,h, Supporting Information). [43] To evaluate the blocking ability of the membranes to anions (especially OH − ), pH of the neutral chamber (catholyte, with an initial pH of 7.21) after cycling is monitored in Figure 5e. Using SPEEK-M, the pH is increased to 11.13 at the 350 th cycle, corresponding to a concentration of ≈10 −3 M for OH − , which means that though the SPEEK-M can block most of the OH − , there is still a certain permeation from the alkaline chamber (anolyte, pH < 0).…”

“…The decrease in ionic conductivity mainly originates from the ionic insulation and hydrophobic properties of the PES. [ 41–43 ] The addition of PES will reduce the proportion of −SO 3 H functional groups, and thus lead to lower conductivity. Yet, PES can densify the SPEEK‐M, which is beneficial to block the permeation of other substances.…”

Design Strategies of 3D Carbon‐Based Electrodes for Charge/Ion Transport in Lithium Ion Battery and Sodium Ion Battery

“…[ 117 ] d) Illustration of the preparation process of the electrode. [ 118 ] a,b) Adapted with permission. [ 113 ] Copyright 2019, American Chemical Society.…”

“…While some improvement in the modification of 3D electrode surface have been studied, the optimized slurry coating process seems more attainable to enhance ion transport within electrode. There are two main categories including process and formulation parameters affect the final morphology of the electrode, [ 118,119 ] determining the electrode's electrochemical performance. Some parameters such as casting solution composition and viscosity, relative humidity, and exposure time to water vapors are important to construct an electrode through the traditional slurry coating process.…”

“…For example, a flexible electrode with a symmetrical structure were obtained by controlling the phase separation rate (Figure 10d). [ 118 ] Such characteristic structure is conductive to the effective exploitation of electrolyte ions. An alternative to promote contact and reaction of the electrode materials with the electrolyte ions is to form the hierarchical porous structure based on the liquid–liquid phase separation of hydrophobic components in the casting process.…”