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

In the rising advent of organic Li-ion cathodes with practical characteristic of being air-stable while in the reduced lithium-reservoir form, we report herein a new class of organic Li-ion positive electrode materials - the conjugated oximate lithium salts. The solid-phase electrochemistry of first five examples of the oximate class, including cyclic (aromatic), acyclic (non-aromatic), aliphatic and tetra-functional stereotypes, uncovers the complex interplay between the molecular structure and the electroactivity in the solid phase, as well as the potential of this rich family as cathode materials for lithium-ion batteries. The conjugation of oximate functions within the molecular core is found to endow excellent air stability of lithiated reduced phases, an important prerequisite for practical use as Li-ion positive electrode materials. Amongst the exotic features characterizing the solid-state electrochemistry of this class of materials, the most appealing one belongs to the reversible solid-state polymerization through intermolecular azodioxy coupling (-ONNO-) and the intramolecular furoxan cyclization of their oxidized forms. In the disclosed series of materials, the best performing candidate delivers high reversible capacity of 357 at an average potential of 3.0 vs. Li+/Li0, attaining over 1 KWh kg-1 specific energy content.