Amide coupled Si-rGO hybrids as anode material for lithium-ion batteries

Abstract

Despite silicon (Si) having a high specific capacity of 4200 mA h/g, it undergoes significant expansion in volume during lithiation. In order to alleviate the significant increase in volume that occurs in silicon nanoparticles (SiNPs) of lithium-ion batteries, herein we report covalently modified SiNP contained within reduced graphene oxide (rGO) sheets as an anode material in lithium-ion batteries (LIBs). The structural modification of SiNP could effectively mitigate the increase in volume while preserving its outstanding electrochemical properties. Graphene oxide (GO) undergoes chemical modification and functionalization by a simple and efficient method using microwave-assisted sonochemical approach. The procedure entails grafting carboxyl functionalized silicon nanoparticles (C-Si) to amine-functionalized reduced graphene oxide (NH2-rGO) to produce a Si-rGO hybrid via amide linkage. This hybrid reduces the problem of volume expansion in Si anodes by dissipating substantial changes in volume and minimizing direct contact between SiNPs and the electrolyte. The formation of a robust solid electrolyte interface (SEI) layer improves the specific capacity and durability of the anode material. We observed that the Si-rGO 2 hybrid (containing 44 wt% Si) exhibited a relatively higher specific capacity of 1604 mA h/g during the initial cycle at C/10 rate when compared to other hybrid systems, such as Si-rGO 1, Si-rGO 2, Si-rGO 3 with bare SiNP, and SRGO composite (without amide linkage). Additionally, it maintained a capacity of approximately 1000 mA h/g at C/2 rate for more than 125 cycles. Thus, enhanced specific capacity, cycling stability, electrode conductivity, and lithiation are made possible due to the structural modification of SiNPs.