Single‐Ion Lithium Conducting Polymers with High Ionic Conductivity Based on Borate Pendant Groups

Abstract

A family of single-ion lithium conducting polymer electrolytes based on highly delocalized borate groups is reported. The effect of the nature of the substituents on the boron atom on the ionic conductivity of the resultant methacrylic polymers was analyzed. To the best of our knowledge the lithium borate polymers endowed with flexible and electron-withdrawing substituents presents the highest ionic conductivity reported for a lithium single-ion conducting homopolymer (1.65 × 10 À 4 S cm À 1 at 60 °C). This together with its high lithium transference number t Li þ = 0.93 and electrochemical stability window of 4.2 V vs Li 0 /Li + show promise for application in lithium batteries. To illustrate this, a lithium borate monomer was integrated into a single-ion gel polymer electrolyte which showed good performance on lithium symmetrical cells (< 0.85 V at � 0.2 mA cm À 2 for 175 h).

Designing Boron‐Based Single‐Ion Gel Polymer Electrolytes for Lithium Batteries by Photopolymerization

“…In this work, three anionic methacrylic monomers based on highly delocalized asymmetric borate groups were synthesized according to Scheme as recently reported. [ 24 ] In the first one, 2‐hydroxyethyl methacrylate was covalently bonded to a boron atom (COB bond) via the dropwise addition of borane tetrahydrofuran complex (BH 3 ‐THF). In the second step, the desired functionality was added to the methacrylic‐molecule via the addition of triethylene glycol monomethyl ether (methyltriglycol) and/or HFP.…”

“…Synthetic route for the preparation of borate‐based single‐ion monomers SIM‐FF, SIM‐FG, and SIM‐GG. [ 24 ] …”

“…Synthetic route for the preparation of borate-based single-ion monomers SIM-FF, SIM-FG, and SIM-GG. [24] Scheme 2. Lithium single-ion polymer electrolyte (SIGPE) synthesis process by UV-photopolymerization.…”

“…[20][21][22] Hence, substituents that improve this chain mobility are desirable for achieving higher conductivities in polymers containing this type of borate group. [23] In this work, single-ion gel polymer electrolytes (SIGPEs) were prepared by UV-photopolymerization based on three borate lithium methacrylate monomers [24] and poly(ethylene glycol) dimethacrylate (PEGDM) and tetraethylene glycol dimethyl ether (tetraglyme, G4) as a plasticizer. The effect of the substituents in the boron atom of the different monomers and the impact of G4 glyme plasticizer on the thermal, mechanical, and electrochemical properties of the developed SIGPEs are deeply analyzed.…”

In situ prepared “polymer-in-salt” electrolytes enabling high-voltage lithium metal batteries

“…[1][2][3] PEs are mostly prepared by dissolving lithium salts in the polymer matrix (known as "salt-in-polymer"), which usually suffers from a narrow electrochemical window and low ionic conductivity at room temperature. [4][5][6] On the other hand, the unsatisfactory lithium ion transference number (t Li +) increases the concentration polarization of Li + , which further inhibits the rapid rate of charging/discharging of solid-state batteries. [7][8][9][10] Alternatively, "polymer-in-salt" electrolyte (PISE) where the content of lithium salt exceeds 50 wt% emerge as a promising solution to extend the electrochemical window, achieve high ionic conductivity at room temperature and prevent dendrite growth at lithium metal anodes.…”