Supporting Information Ultrahigh-rate nickel monosulfide anodes for sodium/potassium-ion storage Milan K. Sadan a , Huihun Kim a , Changhyeon Kim a , Gyu-Bong Cho b , Kwon-Koo Cho b , Jou- Hyeon Ahn b *, and Hyo-Jun Ahn b * a Research Institute for Green Energy Convergence Technology, Gyeongsang National University, Jinju 52828, Republic of Korea b Department of Materials Engineering and Convergence Technology, RIGET, Gyeongsang National University, Jinju 52828, Republic of Korea *Corresponding authors E-mail addresses: ahj@gnu.ac.kr (HJA) and jhahn@gnu.ac.kr (JHA) Electronic Supplementary Material (ESI) for Nanoscale. This journal is © The Royal Society of Chemistry 2021