STEIN RESEARCH GROUP

POROUS SOLIDS — NANOCOMPOSITES — SELF-ASSEMBLED FRAMEWORKS

 

Zinc and Magnesium Manganese Oxides with
High Lithium Insertion Capacity

Zinc and magnesium manganese oxides with high lithium insertion capacity. During our investigations with layered metal oxide guests within mesoporous sieves, we developed a new procedure to synthesize magnesium and zinc substituted birnessites (layered manganese oxides). The synthesis is based on a combination of two simple techniques, co-precipitation and ion-exchange. The materials prepared through the new procedure maintained the layered structure typical of birnessites. The electrochemical characterization of Mg- and Zn-birnessites as host materials for lithium intercalation has shown very promising performance. The maximum lithium insertion capacity of the materials, evaluated from the first discharge at low current density, was greater than 2 F/mol. This represents a significant improvement over existing manganese oxide battery materials, which are of considerable interest in the United States due to their low cost and environmental acceptance. In spite of kinetic limitations due to the non-optimized morphology, Mg-birnessite composite cathodes showed fairly good rate performance by delivering capacity as high as 130 mAh/g and specific energy of more than 350 mWh/g in C/4 rate discharge. The combination of thermodynamic and kinetic properties exhibited by the substituted birnessites compare well with other manganese oxides and these properties are expected to improve upon morphological, compositional and engineering optimizations. Of further importance, the synthesis procedure as well as the materials involved are both environmentally safe, and inexpensive as compared with those currently in use. These factors, combined with the high capacity and energy performance, might contribute to lower the cost of the final devices, rechargeable or single-use lithium batteries.

• Aronson, B. J.; Kinser, A. K.; Passerini, S.; Smyrl, W. H.; Stein, A.; "Synthesis, Characterization, and Electrochemical Properties of Zinc and Magnesium Birnessites Prepared by a Low Temperature Route", Chem. Mater. 1999, 11, 949-957.