Recovery and electrochemical performance in lithium secondary batteries of biochar derived from rice straw.

Renewable biomass has attracted great attention for the production of biooil, biogas, and biochar, a carbon residual applicable for carbon sequestration and environmental remediation. Rice straw is one of the most common biomasses among agricultural wastes in South Korea. As part of our advanced and environmentally friendly research, we applied biochar derived from rice straw as the anode material for lithium-ion batteries (LIBs). Porous carbons with a high surface area were prepared from rice straw. Such porous carbons have exhibited particularly large reversible capacity and hence proven to be a candidate anode material for high-rate and high-capacity LIBs. Rice straw-derived biochars were synthesized at four different temperatures: 400, 550, 700, and 900 °C. The surface was modified by using HCl and H2O2 on the 550 °C biochar in order to increase the surface area. The resulting biochar was characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The surface area was measured by Brunauer-Emmett-Teller (BET) method. The electrochemical characterizations were investigated by galvanostatic charge-discharge (CD) curves, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). All samples exhibited reversible capacities of below 200 mAh g(-1). The surface-modified biochars exhibited improved cycle performance. Surface modification using HCl showed better cycle performance than H2O2. However, the capacities of the treated 550 °C biochar were similar to those of non-surface-modified biochar.