Electrochemical Performance of Highly Ion-Conductive Polymer Electrolyte Membranes Based on Polyoxide-tetrathiol Conetwork for Lithium Metal Batteries

Abstract

A copolymer network consisting of poly(trimethylolpropane ethoxylate triacrylate) oligomer (TMPETA) and pentaerythritol tetrakis (3mercaptopropionate) cross-linker (PETMP, tetrathiol) was photo-cross-linked via "thiol−ene click" reaction. The conetwork (TMPETA-co-PETMP) exhibited a single glass transition temperature (T g ) shifting systematically to a lower temperature with increasing content of tetrathiol cross-linker from −22 °C at 100:0 to −36 °C at the composition of 60:40 ratio by weight %. Polymer electrolyte membranes (PEMs) containing various contents of lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) salt and succinonitrile (SCN) plasticizer were investigated in order to obtain optimum PEM formulation having high ionic conductivity and good mechanical support for use in lithium metal batteries. The optimized PEM composition of (70:30) 20/40/40 (TMPETA-co-PETMP)/SCN/LiTFSI exhibited high room-temperature ionic conductivity of ∼1.8 × 10 −3 S/cm, good mechanical performance, and high Li + transference number of ∼0.76 suggestive of domination by the lithium cation transport, which would alleviate some drawbacks encountered in conventional liquid electrolyte systems. Moreover, the PEM was found to be electrochemically stable up to 5.3 V with excellent cyclability. The specific capacity of 147 mA h g −1 was obtained at 0.1 C from the Li-PEM-LFP cell, exhibiting excellent capacity retention of about 94%. Given the excellent ionic conductivity at ambient, good mechanical integrity, thermal stability, and outstanding electrochemical performance at various operating conditions, the present all-solid-state PEM is an excellent candidate for potential application in high-energy lithium metal batteries.

Developing Single‐Ion Conductive Polymer Electrolytes for High‐Energy‐Density Solid State Batteries

“…Even with the optimization of the polyanions and polymer matrices, the strictest solid‐state SICPEs still hardly achieve ionic conductivities higher than 10 −4 S cm −1 at room temperature. [ 102 ] In addition, the interface issues [ 123 ] between SICPEs and electrodes have yet to be satisfactorily solved. In this case, plasticizers [ 124 ] are usually employed in SICPEs, increasing the free volume in the polymer matrix and dissociating and coordinating with Li + , leading to enhanced segmental mobility and charge carrier concentration.…”

Click Chemistry in Lithium‐Metal Batteries

“…At the same time, PEGDME also exhibits a lower absorption energy toward Li + , hence accelerates Li + transportation. Succinonitrile (SCN) is another useful plasticizer, which can be incorporated with the polymer matrix made by the crosslinked thiol–ene reaction of TMPMP and PEGDA, [ 138 ] PETMP and poly(trimethylolpropane ethoxylate triacrylate) (TMPETA), [ 139 ] as well as thiosiloxane and PEGDA. [ 140 ] SCN owns the ability of dissolving a variety of Li salts due to the high‐polarity nature originating from its plastic crystalline phase.…”

Advances in Electrospun Materials and Methods for Li-Ion Batteries

“…The way in which energy is stored (through mechanisms such as Insertion/Intercalation, Conversion, and Alloying) has a direct impact on the amount of energy that can be stored. To increase capacity, a suitable nanostructure can be constructed as the active material for the electrode [ 3 , 4 ]. The design of nanostructures plays a critical role in providing a shorter ion pathway and effective electrical conduction, thanks to their larger surface area-to-volume ratio and superior mechanical strength.…”