Highly efficient synthesis of nano-Si anode material for Li-ion batteries by a ball-milling assisted low-temperature aluminothermic reduction

A nano-sized Si anode material was synthesized by a novel and highly efficient route of ball-milling assisted low-temperature aluminothermic reduction at 150-180 degrees C in a eutectic NaCl/KCl/AlCl3 mixture, using white carbon black and coarse-grained Al powder as the starting materials. After extending the duration of ball-milling assisted aluminothermic reduction to 10 h, the obtained Si yield reached as high as 94%. The synthesized nano-Si mainly consisted of irregular porous agglomerates constructed by ultrafine primary particles with a particle size less than 50 nm. The nano-Si anode showed a superior electrochemical performance. Its maximum discharge and charge capacities at a current density of 0.05 A g(-1) were 3075 and 2597 mAh g(-1), respectively, leading to a high initial Coulumbic efficiency of 84.5%. The nano-Si anode exhibited reversible capacities of 2458 mAh g(-1) at 0.2 A g(-1), and of 1169 mAh g(-1) at a high current density of 5 A g(-1). After cycling at 1 A g(1) for 400 cycles, it still delivered a high reversible capacity of 804 mAh g(-1). The synthetic strategy, which is not only facile and highly efficient, but also low-cost and environmentally benign, is thus promising to be applied for mass production of nano-Si anode materials for next-generation Li-ion batteries. (C) 2019 Elsevier Ltd. All rights reserved.