Electrochemical behaviour of silver ferrite compounds in Li-ion cells with a fluorine-free electrolyte

Elimination of fluorinated compounds is currently receiving significant attention in the development of safer and less environmentally impacting Li-ion batteries. Here, Delafossite-type silver ferrite nanoparticle compounds with different Ag/Fe ratios, synthesized via room temperature co-precipitation, have been characterized in depth and further studied in Li-ion cells employing a fluorine-free electrolyte and water-soluble binders. The electrochemical reactions of these compounds are investigated via various analyses till very low potentials vs. Li + /Li. This causes drastic structural changes due to irreversible reduction and displacement of Ag + to metallic Ag nanoparticles followed by oxide conversion and further Li-alloying. Such charge storage mechanisms and concomitant pseudocapacitive behavior were identified through the electrochemical curves. Structure alterations and surface reactivity of the materials due to such displacive reactions were evaluated, as well as their influence on solid electrolyte interphase formation and charge losses in 0.8 M lithium bis(oxalato)borate (LiBOB) electrolytes as potential fluorine-free alternative to LiPF 6 . Electrochemical cycling of these compounds using LiBOB as electrolyte highlighted noticeable challenges in capacity stabilization, wherein interface-related shortcomings were mitigated by vinylene carbonate addition, although the main limitations due to their inherent displacive reaction mechanisms persisted. This study offers relevant insights into less investigated silver ferrite compounds as possible anode materials, while aiming here at environmentally friendly and safe routes to both electrode and electrolyte formulations.