Green preparation of porous electrodes containing Si via sublimation and regeneration of nanostructured terephthalic acid for enhanced Li-ion storage

Abstract

Porous structures, such as porous Si electrodes required for high-performance Li-ion batteries, are often produced through environmentally problematic processes. In this study, an innovative approach is employed for the green preparation of high-performance porous Si electrodes via thermal treatment of an electrode composed of Si nanoparticles, polyimide (PI), and nanostructured terephthalic acid (TPA). During the process, TPA sublimes at around 318 °C, resulting in a compact yet porous electrode, enhanced with a cross-linked PI binder. Moreover, TPA can be regenerated through the condensation of vaporised monomers, supporting a circular economy for the clean preparation of the advanced electrode. Despite the simplicity of this method, the resulting electrode (Si@PI@nano-TPA@E-350) exhibits a remarkable Li-ion storage performance, demonstrating a reversible capacity of 2355 mA h g⁻¹ at 0.2 A g⁻¹ after 120 cycles, along with a reduced charge transfer resistance (R_ct) of 99 Ω. This is in contrast to the electrode prepared without TPA (Si@PI@E-350), which only achieves a capacity of 1268 mA h g⁻¹. The morphological features of the TPA used significantly impact the electrode's performance. A full-cell composed of Si@PI@nano-TPA@E-350 as the anode and LiFePO₄ as the cathode exhibits a reversible capacity of 151 mA h g⁻¹ relative to the total mass of the anode and cathode at 0.2 A g⁻¹ after 50 cycles, with a capacity retention of 97.8%, demonstrating an enhanced energy density of 455 W h kg⁻¹. This article presents a green method for sustainably fabricating porous structures for efficient energy storage and a wide range of other applications.