Symmetric Aqueous Batteries of Titanium Hexacyanoferrate in Na+, K+, and Mg2+ Media

Symmetric batteries, in which the same active material is used for positive and negative electrode, simplifying manufacture process reducing fabrication cost, have attracted extensive interest large-scale stationary energy storage. In this paper, we propose a symmetric battery based on titanium hexacyanoferrate (TiHCF) with two well-separated redox peaks of Fe3+/Fe2+ Ti4+/Ti3+ tested it aqueous Na-ion/ K-ion/Mg-ion electrolytes. The result shows that all batteries exhibit voltage plateau centered at around 0.6 V, discharge capacity 30 mAhg−1 C/5. Compared to Mg-ion electrolyte, TiHCF Na-ion K-ion electrolytes better stability. calculated diffusion coefficient Na+, K+, Mg2+ are order magnitude, indicates three-dimensional ionic channels interstices lattice large enough an efficient K+ insertion extraction.