Manganese Sequestration and Li-Ion Batteries Durability Enhancement by Polymeric 18-Crown-6 Ethers

Abstract

We propose trapping of Mn cations by polymeric crown ethers as a mitigation measure for the consequences of Mn dissolution in Li-ion batteries (LIBs). Mn cations trapping by poly(vinylbenzo-18-crown-6) and poly(undecylenyloxymethyl-18-crown-6) was investigated for 1M LiPF6 solutions in binary carbonates containing Mn(II) salts and in lithium manganese oxide (LMO) spinel – graphite (GR) cells. Trapping site occupancies by Mn+2 exceeding 90% were measured in bench top experiments. Polyethylene separators coated with poly(vinylbenzo-18-crown-6) trapped Mn cations in LMO - GR cells and decreased capacity fade during 100 cycles at high temperature (60°C) and C/4 rate, retaining 26% more capacity than the baseline cells. We also address the important distinction between using free (molecular) vs. tethered (polymeric) macrocycles, and its consequences for LIB performance.