Revealing the Reversible Solid-State Electrochemistry of Lithium-Containing Conjugated Oximates: Towards a New Functionality for Organic Batteries

Abstract In the rising advent of organic Li-ion positive electrode materials with increased energy content, chemistries with high redox potential and intrinsic oxidation stability, while in the lithium containing (Li-ion) form, remain a challenge. Molecular engineering of carbonyl compounds and of conjugated sulfonamide chemistries, have provided ground for future developments, while also inciting the search for other organic chemistry functions or classes, with alike properties, and with further improved energy storage metrics. Herein, we report on the solid- phase reversible electrochemistry of a new class of organic redox functionality for batteries, the lithium salts of conjugated oximates. The disclosed first five examples of the oximate class, including cyclic (aromatic), and acyclic (non-aromatic), as well as aliphatic and tetra-functional stereotypes, uncover the complex interplay between the molecular structure and the electroactivity, as well as the potential of this rich family as Li-ion positive electrode materials for batteries. Amongst the exotic features specific to this class of materials, the most appealing one is the reversible electrochemical polymerization – depolymerization accompanying the charge storage process in solid phase, through intermolecular azodioxy coupling (-ONNO-) or the intramolecular furoxan cyclization of the oxidized forms. Over the disclosed materials, the best performing candidate delivers a high reversible capacity of 350 mAh g-1 at an average potential of 3.0 vs. Li+/Li0, attaining 1 kWh kg-1 specific energy content at the material level metric. This work ascertains a strong link between the electrochemistry, organic chemistry and battery science by emphasizing on how different phases, mechanisms and performances can be accessed using a single chemical functionality.