Reversible reduction of Li2CO3

Abstract

Lithium carbonate (Li₂CO₃), either as a product of a conversion reaction or as an important component of the solid-electrolyte interphase (SEI) layer on the anode of a lithium ion (Li-ion) battery, is known to be chemically inactive in both reducing and oxidizing atmospheres. No sufficient evidence has shown that Li₂CO₃ can be reduced, let alone recognize its reduction products. Here we clarify that Li₂CO₃, as a product of a conversion reaction of cobalt carbonate (CoCO₃) upon Li insertion, can indeed be further reduced/converted to lithium carbide (Li₂C₂) and lithium oxide (Li₂O), based on spectroscopic and transmission electron microscopic analyses. These findings will have important guidance to designing electrode (materials) with more stable cycling performances, finding ways to convert some inert compounds into useful electrode materials, and search for electrode materials with higher specific capacities, as well as understanding the excess reversible capacity of some electrode reactions.