Insight into the high-efficiency separation of Si element from low-grade laterite nickel ore and the preparation of Li2FeSiO4/C cathode materials for lithium-ion batteries

Abstract

In the traditional laterite nickel ore treatment process, the recovery focus is mainly on the metal elements, such as Ni, Cr, Mg, Fe, etc. However, the extremely rich Si is usually discharged in the form of waste residue, which makes it far from being fully utilized. In this paper, the alkaline hydrothermal/water leaching method of sodium hydroxide and laterite nickel ore was used to effectively recover silicon. Alkali/ore ratio of 1.2:1, hydrothermal temperature of 250 °C and holding time of 2 h are the optimum process conditions, and the leaching rate of Si can reach more than 98.8% at this condition. In addition, the conversion process of silica-containing sediment was studied, obtaining high purity SiO2. Then, the Li2FeSiO4/C cathode material for Li-ion batteries was successfully prepared by two-stage calcination process using prepared SiO2 as silicon source. The initial discharge capacity of Li2FeSiO4/C can reach 148.5 mAh·g−1 at 0.1 C. Moreover, the discharge specific capacity of Li2FeSiO4/C electrode remained above 125 mAh·g−1 after 200 cycles at 1 C. This whole process doesn’t use any reducing agent and features short process, easy to operate,economic and reasonable, which is conducive to the efficient recovery and reuse of Si element in laterite nickel ore, providing an important way and method for the development of products with high added value and high-tech content of laterite nickel ore resources.