Uniform coating of nano-carbon layer on SiOx in aggregated fluidized bed as high-performance anode material

Abstract

Carbon layer coating is a facile method to improve the electrochemical performance of SiOx. However, few strategies promise a uniform coating. The fluidized bed reactor with high heat and mass transfer efficiency to ensure uniform coating, requires large particles to achieve smooth fluidization. In this study, we bound the raw powders together to form loose secondary particles with a diameter of ∼100 μm, which were supposed to be both fluidized smoothly and also returned to their original size after carbon coating, to achieve a uniform carbon layer coating of ∼15 nm on commercial SiOx powders with a preferable graphitization degree (ID/IG = 1.0) and low surface area (∼2 m2 g−1). The SiOx@C composites delivered a high initial coulombic efficiency (75.1%), an excellent cyclability (83% capacity retention rate for 500 cycles at 1 A g−1), and a superior rate capability (907.7 mAh g−1 at 2 A g−1). The more than 106 increase in electronic conductivity and 104 increase in Li+ diffusion were responsible for the improvement of electrochemical performance. The resistance of the carbon layer to hydrogen fluoride (HF) erosion was observed. This method is suitable for the scaled-up production of anode materials and is expected to be applied to other materials.