Impact of Rare Earth Additions on Transition Metal Oxides as Negative Electrodes for Lithium-Ion Batteries

Transition metal oxides have been proposed as negative electrode material candidates for lithium-ion batteries because they can reversibly react with lithium via a displacement reaction to deliver two to three times the specific capacity of graphite. However, the practical application of transition metal oxides has been frustrated by their inconvenient working potential. Here, the impact of the addition of rare earth (RE) elements to transition metal (TM) oxides as negative electrodes was studied. Thin films of pseudobinary misch-metal-Fe-O libraries (misch metal is a mixture of common RE elements) were prepared by combinatorial sputtering methods. Powdered perovskite-structured RE-TM-O(3) samples, including LaFeO(3), CeFeO(3), and LaCoO(3), were synthesized by solid-state methods. The structural and electrochemical characterizations of these samples are presented here. It was found that the addition of RE elements decreases the working potential of TM oxides. However, the specific capacity is undesirably lowered. (c) 2008 The Electrochemical Society. [DOI: 10.1149/1.2999054] All rights reserved.