ARTICLE
This journal isLithium carbonate (Li 2 CO 3 ), either as a product of the 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 was shown that Li 2 CO 3 can be reduced, let alone to recognize its reduction products. Here we clarify that Li 2 CO 3 , as a product of conversion reaction of cobalt carbonate (CoCO 3 ) upon Li insertion, can indeed be further reduced/converted to lithium carbide (Li 2 C 2 ) and lithium oxide (Li 2 O), 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 to useful electrode materials, and search for electrode materials with higher specific capacities, as well as in understanding the excess reversible capacity of some electrode reactions.