Synthesis and Application of a Conjugated Polydianion‐Based Single‐Ion Conducting Polymer for High‐Performance Solid Lithium‐Ion Batteries

Abstract

Fluorosulfonimide lithium salts have been widely used as conductors in solid polymer electrolytes for solid Li‐ion batteries (LIBs). However, low conductivity and poor compatibility with the polymer host (usually polyethylene oxide, PEO) remain challenges in the design of these salts. In this paper, we synthesized a highly Li+‐conductive salt containing the poly(perfluoroalkylsulfonyl)diimide (PFSDI−) dianion for the first time. LiPFSDI represents the first example of a single Li‐ion‐conducting polymer (SLICP) with a conjugated sulfonimide moiety (−SO2−N(−)−SO2−N(−)−SO2−). The PEO−LiPFSDI blend electrolyte exhibits significant enhancements in ionic conductivity (2.24×10−4 S cm−1 at 80 °C)and electrochemical stability (up to 6 V vs. Li+/Li). A prototype LiFePO4/Li battery with the PEO−LiPFSDI composite electrolyte shows excellent cycling performance with a high reversible capacity of 148 mAh g−1 at a rate of 0.1 C and 135 mAh g−1 at 0.2 C (70 °C), and maintains 100 stable cycles for over 1500 hours.

Macromolecular Design of Lithium Conductive Polymer as Electrolyte for Solid‐State Lithium Batteries

“…Polyanions in reports mainly include alkyl carboxylates, [ 108 ] sulfonates, [ 109 ] sulfonylimides, [ 110,111 ] and borates [ 112 ] in view of immobilized anions. Choosing an appropriate polyanion species is vital to the single‐ion conductor design.…”

Molecular Design of a Highly Stable Single-Ion Conducting Polymer Gel Electrolyte

“…It was shown that Li dendrite growth could be eliminated with a SIC electrolyte of low mechanical strength . Bis­(trifluoromethyl sulfonyl)­imide (TFSI – )-based polymers have been intensively studied because they display weaker coordination between Li + and the anions − compared with other systems, such as those with carboxylate − and sulfonate anions. − Bouchet et al reported the use of a polystyrene (PS)-PEO block copolymer with TFSI – bonded to PS where the microphase-separated PEO molecules are employed for conducting Li + . A t Li + above 0.85 was achieved with an ionic conductivity of 1.3 × 10 –5 S cm –1 at 60 °C.…”