Insight into the Ionic Transport of Solid Polymer Electrolytes in Polyether and Polyester Blends

Abstract

Solid polymer electrolytes (SPEs) have been playing a crucial role in the development of a high-performance solid-state lithium metal battery. The safety and the easy tailoring of the polymers designate these materials as promising candidates to be implemented as electrolytes. Poly(ethylene oxide) (PEO) has been widely employed during the past four decades, but its inferior electrochemical stability against high-voltage cathode active materials strongly urges the search for alternative polymers. In recent years, several carbonyl-containing polymers have arisen as possible replacements for PEO, with poly(ε-caprolactone) (PCL) being one of the most representative. In this work, we combine molecular dynamics simulations and a range of experimental measurements to gain in-depth insights into the ionic transport in polyester-based SPEs. Specifically, the physicochemical properties and morphological behaviors of the blend SPEs comprising PEO and PCL including the two end members are comprehensively investigated. The results reveal that the preferential coordination between Li + cation and ethylene oxide units and partial phase separation between PEO and PCL control the ionic transport in PEO and PCL blends. The present study is believed to inspire novel design strategies for improving the properties of SPEs and batteries made from them.

Ternary Poly(ethylene oxide)/Poly(l,l-lactide) PEO/PLA Blends as High-Temperature Solid Polymer Electrolytes for Lithium Batteries

“…The reason for this increase in lithium transference number associated with the presence of PLA is related to the complexation of the carbonyl groups of PLA with the lithium, which favors the mobility of the cations. This effect has been reported for other systems, for example, in polycarbonates or polyether/polyester blends . Lithium ions coordinate with carbonyl groups, while ethylene oxide groups trap the lithium ions, making their diffusion more difficult through the polymer …”

Electrolyte and anode‐electrolyte interphase in solid‐state lithium metal polymer batteries: A perspective

“…The higher transference numbers of polycarbonate-based SPEs would be linked to the inherent chemistry of carbonate group-lower solvating ability toward lithium salts resulting in strong ion aggregates which could improve the transport of cationic species. 43 Besides, there have been extensive research efforts dedicated to new polymer hosts, such as polymerized ionic liquids (PILs), with/without plastic crystals. These interesting topics have been covered in recent excellent review articles [44][45][46][47] and therefore are not discussed in this article.…”

“…In complement, alternative polymers, such as polyetheramines and polyesters, own advantages in terms of enhancing ionic conductivities at room temperature as compared to PEO due to their amorphous nature. The higher transference numbers of polycarbonate‐based SPEs would be linked to the inherent chemistry of carbonate group—lower solvating ability toward lithium salts resulting in strong ion aggregates which could improve the transport of cationic species 43 . Besides, there have been extensive research efforts dedicated to new polymer hosts, such as polymerized ionic liquids (PILs), with/without plastic crystals.…”

Unveiling Interfacial Li-Ion Dynamics in Li7La3Zr2O12/PEO(LiTFSI) Composite Polymer-Ceramic Solid Electrolytes for All-Solid-State Lithium Batteries

“…34 For the PEO chains, the Optimized Potentials for Liquid Simulations (OPLS) 35 was used to describe bonded and non-bonded interactions, as well as the interatomic interactions with the Li + ions. 36 The interaction parameters for the TFSI − anion were extracted from the force field for ionic liquids developed by Ködermmann and co-workers, 37 but a scaling factor of 0.55 was applied to the charge of nitrogen atoms to ensure electroneutrality in the LiTFSI molecule. For both PEO and TFSI − , non-bonded potentials were the sum of Coulomb and Lennard-Jones (LJ) interactions.…”