Low-Cost High-Energy Potassium Cathode

Potassium has as rich an abundance as sodium in the earth, but the development of a K-ion battery is lagging behind because of the higher mass and larger ionic size of K+ than that of Li+ and Na+, which makes it difficult to identify a high-voltage and high-capacity intercalation cathode host. Here we propose a cyanoperovskite KxMnFe(CN)6 (0 ≤ x ≤ 2) as a potassium cathode: high-spin MnIII/MnII and low-spin FeIII/FeII couples have similar energies and exhibit two close plateaus centered at 3.6 V; two active K+ per formula unit enable a theoretical specific capacity of 156 mAh g–1; Mn and Fe are the two most-desired transition metals for electrodes because they are cheap and environmental friendly. As a powder…

• NS
  National Science Foundation

  Awards: CBET-1438007, DE-AC52-06NA25396, 1438007
• UD
  U.S. Department of Energy

  Awards: DE-SC0005397, DE-AC52-06NA25396, AC52-06NA25396, 7223523
• NN
  National Nuclear Security Administration

  Award: DE-AC52-06NA25396
• DO
  Division of Chemical, Bioengineering, Environmental, and Transport Systems

  Award: CBET-1438007
• BE
  Basic Energy Sciences

  Award: DE-SC0005397
• LB
  Lawrence Berkeley National Laboratory

  Award: 7223523
• LA
  Los Alamos National Laboratory

  Awards: AC52-06NA25396, DE-AC52-06NA25396
• DO
  Division of Materials Sciences and Engineering

  Awards: DE-SC0005397, DE-AC52-06NA25396