Efficient performance optimization of natural graphite enabled by hydrothermal modification with Mg(NO3)2

Abstract

Natural graphite (NG) as the anode material of Li-ion batteries (LIBs) exhibits inferior rate performance and cyclability, affecting its application in high-performance LIBs. Herein, we proposed a hydrothermal modification method to efficiently promote the electrochemical performance of NG in the presence of a Mg(NO₃)₂ modifier. After the hydrothermal modification with 0.4 wt% Mg(NO₃)₂ at 200 °C for 12 h, the modified NG exhibits high capacity retention at high current rates (about 88% at 0.5C relative to the capacity at 0.1C) and excellent cyclability (attaining a reversible capacity of 446.7 mA h g⁻¹ after 350 cycles at 0.3C). Detailed characterization studies demonstrate that the hydrothermal modification with Mg(NO₃)₂ results in an enhanced graphitization degree of NG for improving the structural stability of NG and prolonging the cycle life of the NG anode, additional active sites for storing more Li-ions, and in situ created solid electrolytes of Li₃N, LiN_xO_y and Li₂O for fast Li-ion migration. Moreover, the modification alleviates electrolyte decomposition, Li dendrite formation and polarization during cycling. This hydrothermal modification route is helpful to promote the wide application of NG in the LIBs.