This research investigated the combination of acid functionalization and metal deposition on commercial activated carbon (AC) for the synthesis of electrodes for applications in supercapacitors. The effect of acid treatment and the deposition of metals, including nickel, copper, and cobalt on the electrochemical characteristics of the carbon material were assessed. The AC treatment with sulfuric acid resulted in a nearly twofold increase in surface area compared to the untreated AC, enhancing porosity and creating irregularities that improved the motion of ions and electrons, increasing the specific capacitance and energy density. Notably, we demonstrate that nickel deposition at only 2 wt% significantly improved specific capacitance (up to 59.58 F·g⁻¹), while preserving porosity and enhancing surface wettability. The adoption of a scalable, solvent-free, and low-energy technique for metal deposition on carbon structures presents promising opportunities for developing sustainable alternatives in energy storage technologies.

Cellulose-derived battery separators have emerged as a viable sustainable alternative to conventional synthetic materials like polypropylene and polyethylene. Sourced from renewable and biodegradable materials, cellulose derivatives—such as nanofibers, nanocrystals, cellulose acetate, bacterial cellulose, and regenerated cellulose—exhibit a reduced environmental footprint while enhancing battery safety and performance. One of the key advantages of cellulose is its ability to act as a hybrid separator, using its unique properties to improve the performance and durability of battery systems. These separators can consist of cellulose particles combined with supporting polymers, or even a pure cellulose membrane enhanced by the incorporation of additives. Nevertheless, the manufacturing of cellulose separators encounters obstacles due to the constraints of existing production techniques, including electrospinning, vacuum filtration, and phase inversion. Although these methods are effective, they pose challenges for large-scale industrial application. This review examines the characteristics of cellulose and its derivatives, alongside various processing techniques for fabricating separators and assessing their efficacy in battery applications. Additionally, it will consider the environmental implications and the primary challenges and opportunities associated with the use of cellulose separators in energy storage systems. Ultimately, the review underscores the significance of cellulose-based battery separators as a promising approach that aligns with the increasing demand for sustainable technologies in the energy storage domain.