Life Cycle Assessment of Supercapacitor Electrodes Based on Activated Carbon from Coconut Shells

Abstract

Coconut shells can be used to produce high-performance activated carbon (AC) electrodes for energy storage supercapacitors. An incentive to promote this manufacturing route is sought through its anticipated positive impact on the environment and the substitution of non-renewable resources. The present study sets out to assess the environmental performance of a recently developed route for AC manufacturing through a simple activation process using steam. The analysis was carried out using the life cycle assessment (LCA) approach to investigate the production of AC material and resulting electrodes for a broad range of environmental impact categories and energy use. The study was conducted for a hypothetical optimized industrial-scale scenario drawing on experimental observations, literature, and energy and material balance calculations. Impact assessment results were presented both for the functional unit of electrode’s capacitance and mass of AC and electrode, and interpreted through comparative analyses with coal-derived AC, reduced graphene oxide, and algae-derived biochar aerogel electrodes. The impact assessment results of the new AC electrode show competitive performance across most of the investigated impact categories and indicators. Larger impacts are mostly only observed for the land and water use categories stemming from the agriculturally intensive practice of coconut production. A total of 5.68 kg of CO2 and 34.4 MJ of CED kg–1 AC are reported, with AC constituting roughly 60% of the total impacts arising in the production of supercapacitor electrodes. The results have to be interpreted with present limitations to data especially considering the potentially high variability of carbon content in coconut shell species.

Prospective Life Cycle Assessment of Two Supercapacitor Architectures

“…LCAs, in the field of supercapacitors focusing on the electrode layer, selected the capacitance in Farad (F) as the functional unit. ,, These studies compared different electrode materials and did not consider changes in the components of other supercapacitors’ components. In this context, the choice of capacitance as the functional unit is justifiable.…”

“…LCI of electrode material includes AC powder, PVDF binder, DMSO solvent, and carbon black (Table S2). LCI of biobased AC powder sourced from coconut shells is extracted from previous work . AC powder (4.3 mg) is used to fabricate a 1 cm 2 supercapacitor .…”

“…LCI of biobased AC powder sourced from coconut shells is extracted from previous work. 16 AC powder (4.3 mg) is used to fabricate a 1 cm 2 supercapacitor. 6 LCI of PVDF was collected covering raw materials and energy use during its production; these data were available in published LCA literature.…”

“…Several articles have explored the environmental implications of the electrode layer’s various compositions via the life cycle assessment. LCAs on electrode materials included metal oxides and carbonaceous materials either recovered from waste or sourced from agricultural products. − Two publications have considered the environmental impacts of the entire SC device as part of a more extensive system such as an electric vehicle. However, neither publication has disclosed information about their supercapacitor’s structure and materials. , A dedicated LCA analysis of an entire supercapacitor has been conducted by Cossutta et al, encompassing aluminum as current collectors, 1 M (C 2 H 5 ) 4 NBF 4 in acetonitrile as an organic electrolyte, either activated carbon or graphene as an electrode material and encased in an aluminum housing .…”

Activated Carbon Nanocomposite for Supercapacitor Electrodes

“…Up to now, activated carbon (AC) has been used as commercial electrode material for electrochemical double layer capacitor (EDLC/supercapacitors) and still being researched in the laboratory. AC has some attractive properties such as large surface area, easy to manufacture and abundantly source in nature [2,[6][7]. However, AC has poor electrical conductivity and weak pore connectivity that lowers the ions diffusion pathways.…”