Strategic Structural Design of a Gel Polymer Electrolyte toward a High Efficiency Lithium-Ion Battery

TLDR

Electrolytes are essential for Li‑ion batteries, but liquid forms pose leakage and combustion risks, while solid polymer electrolytes offer safety but low conductivity; gel polymer electrolytes combine the benefits of liquids and solids to improve performance. This review investigates how gel polymer electrolytes can replace liquid electrolytes by examining their structural design and electrochemical properties to assess their potential in Li‑ion batteries. The review outlines the requirements and key electrochemical properties of GPEs, discusses recent advances in common polymer hosts such as polyether, polyvinyl, polynitrile, polycarbonate, and polyacrylate, and explores alternative polymers to meet practical performance demands.

Abstract

Electrolytes have played critical roles in electrochemical energy storage. In Li-ion battery, liquid electrolytes have shown their excellent performances over decades, such as high ionic conductivity (∼10–3 S cm–1) and good contacts with electrodes. However, the use of liquid electrolytes often brought risks associated with leakage and combustion of organic electrolytes. Hence, polymer electrolytes become potential candidates to replace liquid electrolyte systems. Although solid polymer electrolytes (SPEs) offer better safety and good mechanical properties to take over liquid electrolytes, most of them only deliver low ionic conductivities (∼10–8 S cm–1) and poor contact with electrodes, resulting in poor cycle performance and low electrical capacity of the batteries. In addition, gel polymer electrolytes (GPEs) have received increasing research attention due to their relevant characteristics, which extend from liquid electrolytes and solid polymer electrolytes. In this review, state-of-the-art samples of gel polymer electrolytes are elucidated with respect to their structural design and electrochemical properties to determine their application potential in Li-ion batteries (LIBs). First, we present the general requirements of GPEs for LIBs applications, followed by important electrochemical properties of GPEs for LIBs including ionic conductivity, transference number, and ionic transport mechanisms. Furthermore, recent progress of common polymers, namely, polyether, polyvinyl, polynitrile, polycarbonate, and polyacrylate, as polymer host of GPEs has been carefully explained. Finally, the alternative polymers were also discussed to provide new approaches for further developments of GPEs to fulfill the demanded properties for practical applications.