Effect of Thermal Treatment of Poly(amide imide) Binder on Cycling Performance of Silicon Alloy-Based Anode for Lithium-Ion Battery

The growing demand for high-performance rechargeable lithium-ion batteries for applications such as portable electronic devices, electric vehicles and energy storage systems requires remarkable improvement in the energy density. It has led to the search for advanced materials with high theoretical specific capacities, which should be abundantly available for large-scale applications. Silicon-based anode materials with high theoretical capacity, low reduction potential and low cost satisfy these requirements for next-generation lithium-ion batteries.  However, the silicon materials undergo large volume changes during the alloying/de-alloying reaction, resulting in pulverization of the electrode. In addition, the large volume expansion results in the continuous breakdown and formation of solid-electrolyte interphase (SEI) layer during the repeated cycling.  To mitigate the volume change, many studies have been carried out by different approaches such as fabricating thin films, reducing particle size, employing Si alloy materials and using strong binder.  It is well known that binders are critical to maintain the electrode structure and capacity retention.  Different binders for Si-based anodes developed to date include carboxymethyl cellulose (CMC), poly(acrylic acid) (PAA), poly(vinyl alcohol) (PVA), poly(amide imide)(PAI) and polyimide (PI).  Among them, thermally-treated PAI has high mechanical strength and good adhesion, enhancing the electric contact with current collector.  In this study, we report electrochemical characterization of Si alloy materials with thermally-treated PAI as a binder.  Furthermore, we analyzed binding mechanism of PAI, with changing heat treatment temperature. A detailed investigation and evaluation of cycling performances are performed by XPS, FT-IR, electrochemical impedance spectroscopy, peel test and galvanostatic cycling test.