Feasible Fabrication of Carbon Nanotube-Poly(Acrylic Acid) Network Encapsulating Silicon Microparticle for Lithium-Ion Batteries

Recently, the electrification of personal mobility is accelerating the development of Li-ion batteries. With the demands for a lightweight battery, silicon (Si) is considered a strong candidate to achieve high energy density due to its high theoretical capacity (>3600 mAh g^-1). However, the unstable capacity retention of Si anodes is a critical issue for industrial applications. Si particles experience harsh volume changes due to the alloying with the Li ions. This results in the pulverization of Si particles followed by the excessive growth of the solid-electrolyte interphase (SEI) layer. Here, we propose the conductive hybrid network encapsulating Si particles fabricated with a facile slurry-casting method. The functionalized carbon nanotubes (FCNTs) were easily dispersed into water and formed entangled network structures. In addition, poly(acrylic acid) (PAA) enhanced the mechanical properties of the FCNT network and enabled flexible behaviors. This hybrid network uniformly coated Si surfaces and allowed stable connections between the particles providing electron pathways. After the cycle, the pulverized Si particles maintained their morphology with the mechanical supports of the FCNT/PAA network inhibiting the irregular formation of the SEI layer while Si anode with conventional carbon black showed severe destruction of the structure. The electrode with FCNT/PAA network exhibited stable cycle performance during 200cycles and excellent rate capability even at 10C which indicates safe and fast electron transport toward Si particles.