Improved Mechanical Strength without Sacrificing Li-Ion Transport in Polymer Electrolytes

James T Bamford; Seamus D Jones; Nicole S Schauser; Benjamin J Pedretti; Leo W Gordon; Nathaniel A Lynd; Raphaële J Clément; Rachel A Segalman

doi:10.1021/acsmacrolett.4c00158

Improved Mechanical Strength without Sacrificing Li-Ion Transport in Polymer Electrolytes

ACS Macro Lett. 2024 May 21;13(5):638-643. doi: 10.1021/acsmacrolett.4c00158. Epub 2024 May 6.

Authors

James T Bamford^{1

2}, Seamus D Jones^{2

3}, Nicole S Schauser^{1

4}, Benjamin J Pedretti^{5

6}, Leo W Gordon^{1

4}, Nathaniel A Lynd⁵, Raphaële J Clément¹, Rachel A Segalman^{1

2}

Affiliations

¹ Materials Department, University of California, Santa Barbara, Santa Barbara, California 93106, United States.
² Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States.
³ Materials Engineering Department, California Polytechnic State University, San Luis Obispo, California 93106, United States.
⁴ Materials Research Laboratory, University of California, Santa Barbara, Santa Barbara, California 93106, United States.
⁵ McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States.
⁶ Department of Chemical Engineering, Massachusetts Institute of Technology, Boston, Massachusetts 02139, United States.

PMID: 38709178
DOI: 10.1021/acsmacrolett.4c00158

Abstract

Next-generation batteries demand solid polymer electrolytes (SPEs) with rapid ion transport and robust mechanical properties. However, many SPEs with liquid-like Li⁺ transport mechanisms suffer a fundamental trade-off between conductivity and strength. Dynamic polymer networks can improve bulk mechanics with minimal impact to segmental relaxation or ionic conductivity. This study demonstrates a system where a single polymer-bound ligand simultaneously dissociates Li⁺ and forms long-lived Ni²⁺ networks. The polymer comprises an ethylene oxide backbone and imidazole (Im) ligands, blended with Li⁺ and Ni²⁺ salts. Ni²⁺-Im dynamic cross-links result in the formation of a rubbery plateau resulting in, consequently, storage modulus improvement by a factor of 133× with the introduction of Ni²⁺ at r_Ni = 0.08, from 0.014 to 1.907 MPa. Even with Ni²⁺ loading, the high Li⁺ conductivity of 3.7 × 10^-6 S/cm is retained at 90 °C. This work demonstrates that decoupling of ion transport and bulk mechanics can be readily achieved by the addition of multivalent metal cations to polymers with chelating ligands.