The innovation engine for new materials

Wen Jin

Wen Jin


Chemical Engineering


University of California, Santa Barbara


Emily E. Foley

Faculty Sponsor(s): 

Raphaële J. Clément

Faculty Sponsor's Department(s): 


Project Title: 

Manganese- and Iron-based Weberites as High Energy Density Na-ion Battery Cathode Materials

Project Description: 

Li-ion batteries have revolutionized modern life by enabling the widescale utilization of portable electronic devices and electric vehicles. However, lithium is a scarce resource, therefore utilizing more abundant sodium in Na-ion batteries is crucial to the future dependence of sustainable energy sources. Weberites (Na2MIIMIIIF7) are a fascinating class of structures to study as potential cathode materials because of their high structural stability, low 3-D Na-ion diffusion barriers, and wide chemical composition range. Until now, only Na2Fe2F7 has been electrochemically studied and was shown to have remarkably high energy density, cyclability, and rate performance. In an effort to increase the energy density and improve the electrochemical performance of the material, we have created a series of Na2MnxFe2xF7 (x between 0 and 1) compounds based on both Mn2+/Mn3+ and Fe2+/Fe3+ redox. We have synthesized these materials through mechanochemical synthesis followed by an anneal, and have used X-ray diffraction and the Rietveld method to evaluate whether we successfully synthesized our desired material. Following synthesis, we galvanostatically cycled the materials against Na metal in Swagelok cells to retrieve capacity and voltage data that enables us to understand its electrochemical performance. We have found that by increasing the amount of manganese, the stability of the material is decreased leading to longer ball-milling times being needed. In addition, we have replicated similarly high energy density and cyclability as previously demonstrated for Na2Fe­2F7, and have evaluated the electrochemical behavior of new mixed Fe and Mn weberites. These results further suggest that weberite Na2MnxFe2xF7 (x between 0 and 1) materials are very promising cathode materials for Na-ion batteries.