Crystallinity‐controlled SiO _x anode material prepared through a salt‐assisted magnesiothermic reduction for lithium‐ion batteries

Abstract

Summary Silicon suboxides (SiOx) are considered potential anode materials for high‐energy lithium‐ion batteries (LIBs) owing to their high specific capacity and stable cycling performance. Several structural parameters, such as chemical composition, particle size, surface area, and crystallinity, affect the electrochemical performance of SiOx. In particular, the crystallinity of the Si embedded in the SiO2 matrix significantly influences the electrochemical performance of SiOx, as it directly affects the structural stability of Si during cycling. To optimize the high‐performance synthesis of SiOx, we conduct a comparative study of the heat absorbents (KCl and NaCl) to demonstrate their critical role in determining the crystallinity of SiOx particles during the magnesiothermic reduction of SiO. The different heat capacities of these absorbents induced distinctive structural evolutions of SiO during the process, affecting the electrochemical behavior of SiOx during cycling. When KCl was present, the resulted substance has a lower crystallinity of Si, thereby offering superior electrochemical performance compared to that in the presence of NaCl. KCl‐SiOx exhibited a high reversible capacity of 1862 mAh g−1 and an initial Coulomb efficiency (ICE) of 83.0%. Moreover, a stable cycle performance of up to 200 cycles and high capacity retention of up to 89.1% at a current density of 750 mA g−1 could be achieved. Therefore, we believe that the results obtained herein will provide a basis for the development of high‐performance SiOx anode materials for commercial applications.