Investigation of the Conductivity Effect on Silicon Anode Performance for Lithium Ion Batteries

Abstract

The early development on rechargeable lithium battery began with lithium (Li) metal and Sony put into the market the first lithium ion batteries in 1991. Since that date the graphite has been used as commercial anode with the practiable capacity of 250 mAh/g and it has been yet reached the 290 mAh/g in 2015 [1]. In the development of high capacity anode materials for lithium ion batteries, silicon is apparently very promising as anode material due to its high theoretical capacity ~4200 mAh/g. However, the huge volume change (~300%) occurs during the cycling and it results breakdown of the conductive network of the composite electrode. This causes the electrical contact problem between conductive agent and the current collector, resulting low Coulombic efficiency and poor capacity retention for silicon-based lithium ion batteries (LIBs). Polypyrene (Ppr) polymer has much concern recently not only the conductivity and other electrical properties but also thermal stability and mechanical properties. In this study, the aim is to enhance the conductivity of Si electrode which is crucial for charge-discharge rate of a battery. The high conductivity provides fast charge-discharge and that is very important for consumer electronics and electric vehicle applications. For this purpose, the conductive Ppr was synthesized through the free-radical polymerization of the acrylate backbone in the presence of an initiator. It was used as a conductive polymer for silicon anode in LIBs. The conductivity of anode was also studied with different carbonecous additives (carbon black, super p and carbon nanotube). The cells were fabricated as half and full cell. Li was used as the counter electrode for half-cell and NCA was used as the cathode for full cell. Table 1. Experimental results for the conductivity study of Si anode Experiment No Composition Ratio Active Material Binder Conductive additive 1 90:10 Si Ppr - 2 85:15 Si Ppr - 3 85:10:5 Si Ppr CB 4 85:10:5 Si Ppr SP 5 85:10:5 Si Ppr CNT 6 85:10:5 Si PVDF CB