Application of E-field on block copolymers bearing a liquid crystal block as solid polymer electrolytes for lithium metal batteries

Details

Supervisors

Gohy, Jean-François

Faculty

Faculté des sciences

Degree label

Master [120] en sciences chimiques, à finalité spécialisée: chimie de l'industrie

Abstract

Current lithium-ion batteries (LIB) present limitations in terms of energy density and safety, hindering their widespread adoption in applications such as electric vehicles. Lithium metal batteries (LMB) haven been proposed, offering improved performance and enhanced safety. LMB differ from conventional LIB in their composition of anode, cathode, and electrolyte. These fundamental distinctions confer several advantages, making them inherently safer, more stable, and less likely to present risks of fire or leakage. Additionally, LMB offer higher energy density making them suitable for high energy demanding applications. This project involves the synthesis of liquid crystal (LC) monomers and subsequent polymerization via reversible addition-fragmentation chain transfer (RAFT) to generate a macro chain transfer agent. Additionally, block copolymers (BCPs) are synthesized, incorporating one block of LC and a second block consisting of an ionic conductive component derived from ethylene oxide units. Upon subjecting the BCPs to a strong electric field, alignment of the LC side chains occurs, facilitating the formation of nano-channels. The approach is to enhance the ionic conductivity, which obeys Arrhenius-type behavior, via ion hopping along the amorphous structure in an ordered morphology, resulting from the self-assembly of the orientated mesogens. The designed polymer matrix is able to dissolve lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt up to 44 wt% and form a self‑standing film. This process results in a notable enhancement of ionic conductivity from an initial value of 3*10-5 to 1*10-4 S*cm-1 at 60°C.