Si anode with high initial Coulombic efficiency, long cycle life, and superior rate capability by integrated utilization of graphene and pitch-based carbon.

ABSTRACT

A variety of strategies have been developed to enhance the cycling stability of Si-based anodes in lithium-ion batteries. Although significant progress has been made in enhancing the cycling stability of Si-based anodes, the low initial Coulombic efficiency (ICE) remains a significant challenge to their commercial application. Herein, pitch-based carbon (C) coated Si nanoparticles (NPs) were wrapped by graphene (G) to obtain Si@C/G composite with a small specific surface area of 11.3 m2g-1, resulting in a high ICE of 91.2% at 500 mA g-1. Moreover, the integrated utilization of graphene and soft carbon derived from the low-cost petroleum pitch strongly promotes the electrical conductivity, structure stability, and reaction kinetics of Si NPs. Consequently, the synthesized Si@C/G with a Si loading of 54.7% delivers large reversible capacity (1191 mAh g-1at 500 mA g-1), long cycle life over 200 cycles (a capacity retention of 87.1%), and superior rate capability (952 mAh g-1at 1500 mA g-1). When coupled with a homemade LiNi0.8Co0.1Mn0.1O2(NCM811) cathode in a full cell, it exhibits a promising cycling stability for 200 cycles. This work presents an innovative approach for the manufacture of Si-based anode materials with commercial application.