Reversible Mg-Ion Insertion in a Metastable One-Dimensional Polymorph of V2O5
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© 2017 Elsevier Inc. The Li-ion paradigm of battery technology is constrained by the monovalency of the Li ion. A straightforward solution is to transition to multivalent-ion chemistries, where Mg2+ is the most obvious candidate because of its size and mass. The realization of Mg batteries has faced myriad obstacles, including a sparse selection of cathode materials demonstrating the ability to reversibly insert divalent ions. Here, we provide evidence of reversible topochemical and electrochemical insertion of Mg2+ into a metastable one-dimensional polymorph of V2O5 up to a capacity of 0.33 Mg2+ per formula unit. An electrochemical capacity of 90 mA hr g−1 was retained after 100 cycles with an average operating potential of 1.65 V versus Mg2+/Mg0. Not only does ζ-V2O5 represent a rare addition to the pantheon of functional Mg battery cathode materials, but it is also distinctive in exhibiting a combination of high stability, high specific capacity, and moderately high operating voltage. The worldwide push to advance renewable energy is limited by the availability of energy storage vectors. Currently, Li-ion technology dominates; however, the safety and long-term criticality of Li remain serious concerns. Mg is much more abundant than Li, has a higher melting point, and does not form dendrites, making it a safer and more environmentally sustainable choice for intercalation batteries. The improved safety further allows for the use of Mg anodes, leading to a 6-fold increase in specific energy density at the anode. The development of Mg-ion intercalation batteries has been plagued by a dearth of suitable cathode chemistries. Here, we describe a metastable cathode material that is one of the few materials capable of reversibly inserting Mg2+ and elucidate the chemical mechanisms of insertion with an eye toward developing high-energy-density and high-cycle-performance cathode materials for the realization of Mg-ion batteries. Compared with Li-ion batteries, Mg-ion batteries would represent a transformative advance in terms of safety, cost, and performance. Achieving the reversible storage of divalent Mg ions within solid-state frameworks has been exceedingly difficult. Here, Banerjee and colleagues have designed a cathode material that combines high voltage, high capacity, and excellent cycle stability for Mg-ion batteries. They provide definitive evidence of reversible Mg-ion insertion within a metastable V2O5 cathode material, illustrating the use of metastable phase space for realizing novel function.
author list (cited authors)
Andrews, J. L., Mukherjee, A., Yoo, H. D., Parija, A., Marley, P. M., Fakra, S., ... Banerjee, S.