Upcycling Plastic Waste into Porous Activated Carbon As Cathode Material for Lithium-Selenium Batteries

Selenium (Se) has a high specific capacity, rendering it a promising cathode material for rechargeable lithium (Li) batteries. Yet, challenges arise due to irreversible reactions and the shuttle effect in contact with electrolytes. This study addresses these issues by confining Se within a microporous carbon derived from non-recyclable plastic waste through a two-step carbonization/activation process. The resulting plastic waste-derived carbon (PWC) serves as a host for Se, forming cathode composites through a melt diffusion process. The cathode electrode was fabricated using a slurry casting method, comprising PWC/Se composite, carbon black, and sodium alginate (8:1:1 mass ratio). The evolution of the porous structure in PWC and its impact on the electrochemical performance of PWC/Se electrode were investigated for different activation temperatures (500, 600, 700, and 800 °C). The study revealed that the structure of PWC activated below 800 °C consists of mainly micropores. Moreover, by increasing the activation temperature, the specific surface area and pore volume increased, and pore size distribution shifted towards mesoporous structure. The Li-Se coin cell made from PWC activated at 600 °C (PWC600) demonstrated superior discharge capacity (640 mAh g –1 at 0.1C after 400 cycles), rate capability, and long cycling stability at higher current densities. The microporous features of PWC600 were crucial for effective Se confinement, lithium-ion diffusion, and charge transfer. This work emphasizes the sustainable development of microporous carbon from upcycled plastic waste as a promising cathode material for high-energy Li-Se batteries. Our findings contribute to environmentally friendly energy storage solutions and the circular economy by repurposing non-recyclable plastic waste into valuable materials.