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).

Single-Ion Conducting Polymeric Protective Interlayer for Stable Solid Lithium-Metal Batteries

“…Such results demonstrate the superior stability at the electrode/electrolyte interface in typical SIPPI-protected Li-metal anodes, which results in the decreased overpotential of the Li@SIPPI/PVEC/SIPPI@Li cell with increasing cycle number at the beginning. As shown in Figure f, compared to previously reported solid-state electrolyte-based Li/Li symmetric cells, the SIPPI-based symmetric cell exhibits significantly longer cycling life with high current density (3 mA cm –2 ) and improved cationic transport number (0.79). ,,,,,,,− …”

“…EIS plots of the (d) Li/PVEC/Li cell with the SIPPI and (e) Li/PVEC/Li cell after cycling at 25 °C. (f) Comparison of cycle life of Li/Li symmetric cells in this work with the previously reported polymer electrolytes. ,,,,,,,− …”

Current Trends and Perspectives of Polymers in Batteries

“…To circumvent this issue, new low-T g single-ion conductors such as lithium borate containing polymers have recently been developed which show ionic conductivity values close to the PEO polymer electrolytes while showing lithium transference numbers close to 0.9. 50 So far, most of the efforts were devoted to develop polymers with improved electrochemical properties (ionic conductivity, electrochemical window, and lithium transference numbers). However, there are aspects related to sustainability, circularity, or carbon neutrality of the polymers used as polymer electrolytes that are increasingly important.…”

Ion transport and conduction in metal–organic framework glasses

“…115 Alternatively, the anion of a metal salt could be covalently tethered to the organic ligand in a strategy analogous to that of single ion conductors for polymer electrolytes. 116,117 Prospective applications…”