Design Principles of Functional Polymer Separators for High‐Energy, Metal‐Based Batteries

Abstract

Next-generation rechargeable batteries that offer high energy density, efficiency, and reversibility rely on cell configurations that enable synergistic operations of individual components. They must also address multiple emerging challenges,which include electrochemical stability, transport efficiency, safety, and active material loss. The perspective of this Review is that rational design of the polymeric separator, which is used widely in rechargeable batteries, provides a rich set of opportunities for new innovations that should enable batteries to meet many of these needs. This perspective is different from the conventional view of the polymer separator as an inert/passive unit in a battery, which has the sole function to prevent direct contact between electrically conductivecomponents that form the battery anode and cathode. Polymer separators, which serve as the core component in a battery, bridge the electrodes and the electrolyte with a large surface contact that can be utilized to apply desirable functions. This Review focuses specifically on recent advances in polymer separator systems, with a detailed analysis of several embedded functional agents that are incorporated to improve mechanical robustness, regulate ion and mass transport, and retard flammability. The discussion is also extended to new composite separator concepts that are designated traditionally as polymer/gel electrolytes.

Dendrite Growth Suppression by Zn2+‐Integrated Nafion Ionomer Membranes: Beyond Porous Separators toward Aqueous Zn/V2O5 Batteries with Extended Cycle Life

“…This is schematically shown in Figure a. The dendrite suppressing nature of single‐ion conducting electrolytes is already proved in the literature …”

Recent Advances in Materials and Design of Electrochemically Rechargeable Zinc–Air Batteries

“…Although an extended battery lifetime was obtained using modified separators, the high cost of Nafion and ionic liquids limit their practical applications. It is desirable to develop more cost‐effective methods to further improve the ionic conductivity and ion selectivity of separators …”

Smart Materials and Design toward Safe and Durable Lithium Ion Batteries

“…Conventional polymer separators, however, cannot effectively prevent the dendrite formation. Strategies to achieve “dendrite‐free” separators mainly include: 1) developing polymer separators with higher strength and a higher Young's modulus; and 2) homogenizing the ion flux in separators through a precisely designed nanoporous structure . In addition, endowing the separators with early‐detection or functional groups against lithium dendrite growth is also an important strategy that has recently emerged.…”