Valorization of local Indonesian sago starch into hard carbon as anode materials for sodium-ion batteries

<title>Abstract</title> <p> One of the main problems for the development of sodium ion batteries (SIBs) is the absence of suitable anode materials. Hard carbons can be one of the alternative anodes due to the some specific properties such as the large interlayer spacing, disordered and non graphitic structures. Furthermore, hard carbons can be prepared by using various carbon precursors such as biomass resources. In this work, the valorization of one of the local indonesian starch known as sago starch into hard carbon materials were conducted by three synthesis routes such as the direct carbonization, hydrothermal treatment and hydrothermal treatment with urea addition, each followed by pyrolysis carbonization at 1000°C. As prepared materials were then examined as anodes for SIBs by using electrochemical measurements such as cyclic voltammetry (CV) and galvanostatic charge discharge (GCD). Among them, the hard carbon derived from the urea-assisted hydrothermal route exhibited a 1st cycle discharge capacity of 388 mAh g ^− 1 with coulombic efficiency of 69%. It can maintain a stable cycle profiles with high reversible capacity of 265 mAh g ^− 1 after 100 cycles at a current density of 100 mAg ^− 1 . Those well improved electrochemical characteristics were attributed to simultaneous effects of the presence of nitrogen doping which can provide more spaces for adsorption of sodium ions as well as to incease the conductivity, large interlayer spacing, sphere-like morphology, and low surface area. The result indicates the prospective potential of the sago starch-derived hard carbons as anodes for sodium ion battery. </p>