Stable and High-Capacity Si Electrodes with Free-Standing Architecture for Lithium-Ion Batteries

To meet the increasing demands of electric vehicle applications for long ranges, Si-based materials have been intensively investigated as promising candidates for outstanding anodes of lithium-ion batteries over the past 2 decades. In the meantime, various nanotechnologies enable accommodation of the huge volume change of Si during charge/discharge processes, which significantly improves the performances of Si-based anodes. However, a large amount of binders and conductive agents are still required for the reliable performance of Si anodes. Herein, we have introduced freestanding Si electrodes, which show suppressed swelling property (31.29%) after the 100th cycle in spite of no binders. Carbon-coated Si nanoparticle (NP) via thermal decomposition of acetylene (C2H2) gas was confined in the bundles of copper nanowires (Cu NWs) that provide not only high electrical conductivity but also accommodation of volume changes of Si NPs. The carbon coating layer helped to form a stable solid electrolyte interface (SEI) layer on the surface of Si NPs. Furthermore, two-dimensional reduced graphene oxide effectively combines Si NPs and Cu NWs, which maintains the electron pathway and structural stability of electrodes during cycling. As a result, the free-standing Si anodes showed high capacity (1942 mAh g(si)(-1) at the initial cycle) as well as long cycle stability (1753 mAh g(si)(-1), at 200 cycles, 90.26%), based on acceptable impedance data of lower charge transfer resistance (27.57 Omega) and higher diffusion coefficient (35.61 x 10(13) cm(2).s(-1)). Our approach suggests that the formation of stable SEI layers and accommodation of volume expansion have to be considered together for high capacity and long cycling Si anodes.