Efficient and Inexpensive Sodium–Magnesium Hybrid Battery
journal contributionposted on 10.11.2015 by Marc Walter, Kostiantyn V. Kravchyk, Maria Ibáñez, Maksym V. Kovalenko
Any type of content formally published in an academic journal, usually following a peer-review process.
We present a hybrid intercalation battery based on a sodium/magnesium (Na/Mg) dual salt electrolyte, metallic magnesium anode, and a cathode based on FeS2 nanocrystals (NCs). Compared to lithium or sodium, metallic magnesium anode is safer due to dendrite-free electroplating and offers extremely high volumetric (3833 mAh cm–3) and gravimetric capacities (2205 mAh g–1). Na-ion cathodes, FeS2 NCs in the present study, may serve as attractive alternatives to Mg-ion cathodes due to the higher voltage of operation and fast, highly reversible insertion of Na-ions. In this proof-of-concept study, electrochemical cycling of the Na/Mg hybrid battery was characterized by high rate capability, high Coulombic efficiency of 99.8%, and high energy density. In particular, with an average discharge voltage of ∼1.1 V and a cathodic capacity of 189 mAh g–1 at a current of 200 mA g–1, the presented Mg/FeS2 hybrid battery delivers energy densities of up to 210 Wh kg–1, comparable to commercial Li-ion batteries and approximately twice as high as state-of-the-art Mg-ion batteries based on Mo6S8 cathodes. Further significant gains in the energy density are expected from the development of Na/Mg electrolytes with a broader electrochemical stability window. Fully based on Earth-abundant elements, hybrid Na–Mg batteries are highly promising for large-scale stationary energy storage.