(Invited) Beyond Si and SiO x : SiN x and SiC x Anode Materials for Lithium-Ion Batteries

Abstract

The research of silicon (Si) anode with commercial feasibility for high energy lithium ion batteries continues to accelerate because of its high specific capacity of 3592 mAh g-1. Since the massive volume change upon repeated charging-dischrage process turned out as the main origin of insufficient cycling stability, the various material designs has recently been proposed. Nanostructure engineering has been spotlighted because the stress is highly mitigated during lithiation when its size decreases to the nano level. However, although theoretical simulation results have concluded that the size of silicon with quantum level (1~5 nm) shows extremely low stress evolution during (de)lithiation process, previously reported Si-based anodes have been too much focusing on void space or morphological properties with the size of over 10 nm. Alternatively, phase control of active-inacitve matrix has received considerable attention because the nano-engineering advantages (low stress intensification) are strenthened and the nano-property weakenesses (low tap density, high surface area and poor elecrical properties) are compensated simultaneously. For example, micron-sized SiO x consisting of nano-Si (active matrix) with the size of the under 5 nm and SiO1-2 (inactive matrix) has been highlighted owing to its high cycling performance and tap density. Nevertheless, its utilization as a commercial anodes are still hindered by its inferior battery performance including low coulombic efficiency of < 85% caused by intrinsic characteristics of inactive matrix (irreversible formation of Li2O and Li4SiO4). As a result, there is strong motivation to develop the technology realizing the silicon size up to the quantum dot level (1~5 nm) in addition to the phase control of fascinating inacitve matrix. In this aspect, the SiNx and SiCx anodes will be proposed as alternative high capacity anodes with commercial feasibility for high energy lithium ion batteries. In addition to its fundamental features and variety of strategies according to the synthetic method, the critical factors affecting the electrochemical performances of SiN x and SiC x anodes will be covered. Furthermore, these anodes will be compared with the state of the art benchmarking samples including SiOx and Si-carbon composites under the industrial standard conditions.