In situ formed graphene oxide-polyacrylic acid composite cage on silicon microparticles for lithium ion batteries via esterification reaction

To meet the ever growing demand for high energy density and high power density lithium ion batteries, silicon (Si) has been spotlighted as a promising anode material due to its high theoretical specific capacity. However, the practical use of Si anode is hindered by the large volume change during lithiation/delithiation process and resultant electrode pulverization. A significant progress has been made using nanostructured Si-based materials, but their low initial coulombic efficiency and low volumetric capacity are undesirable for practical applications. Si microparticles (SiMPs) are considered as an alternative because of low cost, commercially availability, and high tap density. Herein, we introduced a novel concept of in situ formation of graphene oxide (GO)-polyacrylic acid (PAA) composite cage encapsulating the silicon microparticles (SiMPs) as an anode for LIBs. The mechanically robust covalent bond was formed between carboxylic acid group of PAA binder and hydroxyl group of GO through an esterification reaction. The ester bonded GO-PAA cage confined the pulverized SiMP within and maintained the structural integrity resulting in high Coulombic efficiency, excellent capacity retention, and high rate capability. As-fabricated electrode delivered a high capacity of 2300 mAh g-1 after 200 cycles at a high current density of 1000 mA g-1. Furthermore, a stable cycling has been achieved in a high Si mass loading (1.98 mAh cm-2 after 500 cycles) and in a full cell (1.45 mAh cm-2 after 100 cycles).