Understanding acid pretreatment of lotus leaves to prepare hard carbons as anodes for sodium ion batteries

Lotus leaves are pretreated by exposure to hydrochloric acid (HCl) by several methods, including mild (PHT), hydrothermal (HHT), and mild and hydrothermal (PHHT) treatments, and subsequently pyrolyzed to yield hard carbon materials. The hydrothermal pretreatment produces the most substantial impact on the microstructures, surface compositions, and electrochemical performances of the resulting hard carbons. Materials prepared by the HHT...