A low-cost and high-energy aqueous potassium-ion battery
Raphael L. Streng, Tim Steeger, Anatoliy Senyshyn, Steffen Abel, Peter M. Schneider, Christine Benning, Bernardo Miller Naranjo, David Gryc, Mian Zahid Hussain, Oliver Lieleg, Martin Elsner, Aliaksandr S. Bandarenka, Katarina Cicvarić
Abstract
A sustainable aqueous potassium-ion battery was developed using manganese hexacyanoferrate and other cost-efficient materials, achieving high energy density and longevity enabled by Fe-doping, crystallinity improvement, and electrolyte optimization. To address challenges related to the intermittency of renewable energy sources, aqueous potassium-ion batteries (AKIBs) are a promising and sustainable alternative to conventional systems for large-scale energy storage. To enable their practical application, maximizing energy density and longevity while minimizing production and material costs is a key goal. In this work, we propose an AKIB consisting only of abundant and cost-efficient materials, which delivers a high energy density of more than 70 Wh kg −1 . We combine simple strategies to stabilize the Mn-rich Prussian blue analog cathode by Fe-doping, improving the crystallinity, and tuning the electrolyte composition without employing expensive water-in-salt electrolytes. Using a mixed 2.5 M Ca(NO 3 ) 2 + 1.5 M KNO 3 electrolyte, we assemble a novel AKIB with a Fe-doped manganese hexacyanoferrate cathode and an organic poly(naphthalene-4-formyl-ethylenediamine) anode. Besides a high energy density, the full cell delivers a specific capacity of approximately 60 mA h g −1 , a power density of 5000 W kg −1 , and 80% capacity retention after 600 cycles.