With gradually increasing cost and shrinking crustal abundance for lithium ion batteries (LIBs), it is necessary to develop potassium ion batteries (PIBs) and explore suitable electrode materials for advanced PIBs....

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After the publication of our article [1], it was brought to our attention that the legend of Fig. 3 should have included ''Figs. 3a and 3b are adapted with permission from J. Phys. Soc. Jpn. 71, 491 (2002). Copyrighted by the Physical Society of Japan''. We apologize for this omission.