Study of the electrical conductivity of biobased carbonaceous powder materials under moderate pressure for the application as electrode materials in energy storage technologies

Abstract

This study focusses on the assessment of the electrical conductivity (EC) of biobased electrode materials for the application in energy storage devices and presents a simple and reproducible method to measure the EC of carbonaceous powders under moderate pressure (10–50 N). Based on the pyrolysis of corncob at three different temperatures (600, 800, and 900°C) and further treatments of the biochar obtained at 600°C, 11 different carbonaceous powder materials were produced including biochars, activated carbons, and composites. Composite materials were obtained by adding either metal oxide (RuO2 or Fe3O4) in different proportions or additives which are commonly used in electrode production (5 wt% binder and 15 wt% conductive additive). Furthermore, one physically activated commercial AC based on peat with a known EC of 33 S/m was treated with additives and used as a reference. For all materials, an increase of applied pressure resulted in higher EC values due to closer particle contact. The comparison of two methods (with and without preload) showed that a prepelletization of the samples is not necessary to obtain reliable results. By analyzing the obtained EC values while taking mechanical and physicochemical properties into account, it could be shown that a high carbonization temperature and high specific surface area favor the increase of EC. Furthermore, certain proportions of metal oxides lead to an improvement of EC (40 wt% RuO2, 10 wt% Fe3O4), while the treatment with additives leads to a decrease of EC. The EC values among all samples varied between 0.8 S/m (biochar) and 408 S/m (AC/RuO2 composite) at the highest pressure level (637 kPa). Thus, promising biobased electrode materials for environmentally friendly energy storage technologies are presented with the aim of contributing to the establishment of a biobased resource and product platform for bioeconomy.

Conductive Carbon Materials from the Hydrothermal Carbonization of Vineyard Residues for the Application in Electrochemical Double-Layer Capacitors (EDLCs) and Direct Carbon Fuel Cells (DCFCs)

“…A higher p forces the carbon particles closer to each other, resulting in more surface contacts (=higher contact area), and hence an improved EC. This has already been observed by several researchers [21,29,71,72,73,74].…”

“…This could be explained by the decrease in ρ with higher HTC temperature, since the lower the ρ, the lower the particle contact area, and thus the EC value [21,79]. However, this assumption is contradicted by the observation that the influence of temperature on EC seems to be much higher than the influence of the ρ on EC (see Figure 11C).…”

“…Furthermore, it has been shown that microporous structures are correlated with higher capacities [16], as well as N- and O-containing surface functionalities due to pseudo-capacitive contributions [17,18,19]. High C contents and crystallographic structures of the carbon structure are also favourable for high capacities, because they lead to higher EC values of the respective carbon [20,21].…”

Electrical Resistivity of Carbonaceous Bed Material at High Temperature

“…Biomass and its derivatives (e.g., charcoal) are considered as a possible feedstock to reduce anthropogenic CO 2 emissions produced in industry. Besides its common usage as an energy carrier in power production, charcoal can be used as base material in fuel cells [1], batteries [2], soil amendment [3,4], and as a carbon source in metallurgical industry [5][6][7][8][9][10]. In the latter, fossil fuels such as anthracite, coal, coal char, semi-coke, petroleum coke, and metallurgical coke are the main reducing agents.…”

Biobased value chains for a growing bioeconomy

“…Horlamus et al () have developed a Cellvibrio japonicus strain that can produce rhamnolipids directly from hemicelluloses in a one‐step bioconversion process. Hoffmann, Rodriguez Correa, Sautter, Maringolo, and Kruse () have produced carbonaceous powder materials from lignocellulosic biomass and investigated their electrical conductivity for application as electrode materials in energy storage technologies. It is also possible to feed side streams of other lignocellulosic biomass processing units into biorefineries.…”