Flexible/Rechargeable Zn–Air Batteries Based on Multifunctional Heteronanomat Architecture

Abstract

The increasing demand for advanced rechargeable batteries spurs development of new power sources beyond currently most widespread lithium-ion batteries. Here, we demonstrate a new class of flexible/rechargeable zinc (Zn)-air batteries based on multifunctional heteronanomat architecture as a scalable/versatile strategy to address this issue. In contrast to conventional electrodes that are mostly prepared by slurry-casting techniques, heteronanomat (denoted as "HM") framework-supported electrodes are fabricated through one-pot concurrent electrospraying (for electrode powders/single-walled carbon nanotubes (SWCNTs)) and electrospinning (for polyetherimide (PEI) nanofibers) process. Zn powders (in anodes) and rambutan-shaped cobalt oxide (CoO)/multiwalled carbon nanotube (MWCNT) composite powders (in cathodes) are used as electrode active materials for proof of concept. The Zn (or CoO/MWCNT) powders are densely packed and spatially bound by the all-fibrous HM frameworks that consist of PEI nanofibers (for structural stability)/SWCNTs (for electrical conduction) networks, leading to the formation of three-dimensional bicontinuous ion/electron transport channels in the electrodes. The HM electrodes are assembled with cross-linked polyvinyl alcohol/polyvinyl acrylic acid gel polymer electrolytes (acting as zincate ion crossover-suppressing, permselective separator membranes). Benefiting from its unique structure and chemical functionalities, the HM-structured Zn-air cell significantly improves mechanical flexibility and electrochemical rechargeability, which are difficult to achieve with conventional Zn-air battery technologies.

Recent Advances on Electrospun Nanomaterials for Zinc–Air Batteries

“…For instance, a heteronanomat (HM) structure of zinc anode is prepared in one step by combining the polyetherimide (PEI) electrospun nanofibers and the zinc powder/single‐walled carbon nanotubes (SWCNTs) hybrid (Figure 4e). [ 55 ] A porous dimensional structure can be formed to promote the mass transport, which can be observed in the prepared HM zinc anode (Figure 4f). The HM zinc anode can exhibit an outstanding flexibility even after 1000 cycles of bending–twisting tests.…”

Toward Flexible Zinc–Air Batteries with Self‐Supported Air Electrodes

“…Beyond electrode/electrolyte of single component, multicomponent architecture of both electrodes/electrolyte demonstrated a new class of flexible ZAB is likely to address the abovementioned challenges. [147] Specifically, active materials (Zn powders for zinc electrode, Co 3 O 4 )/multiwalled CNT for air electrode) incorporated carbon fiber-supported electrodes were fabricated through one-pot electrospraying (for active materials) and electrospinning (for nanofibers) process, as shown in Figure 7c. These multicomponent electrodes served multifunctionalities as binders and 3D ion/electron transport pathways.…”

“…Reproduced with permission. [147] Copyright 2018, ACS Publications. e) Schematic diagram of the fabrication for planar stretchable/flexible ZAB array.…”

“…d) Galvanostatic discharge/charge cycling profiles during bending and twisting. Reproduced with permission [147]. Copyright 2018, ACS Publications.…”

Observation of Water Consumption in Zn–air Secondary Batteries

“…As the solvent (water) gradually decreases in the cell, the resistance of cell operation increases, causing the battery to be inoperable at the end. Polyacrylic acid and its counter anions are super absorbent polymers [6,7] that are used to hold water as a gelling agent for the battery [8][9][10]. Although the gelling agent prevents water from rapid evaporation, adding a gelling agent to the solution increases the resistance of the battery, which consequently affects its cycle life.…”