Mesoporous Carbons from Polysaccharides and Their Use in Li-O2 Batteries

Abstract

Previous studies have demonstrated that the mesoporosity of carbon material obtained by the Starbon® process from starch-formed by amylose and amylopectin can be tuned by controlling this ratio (the higher the amylose, the higher the mesoporosity). This study shows that starch type can also be an important parameter to control this mesoporosity. Carbons with controlled mesoporosity (Vmeso from 0.1–0.7 cm3/g) have been produced by the pre-mixing of different starches using an ionic liquid (IL) followed by a modified Starbon® process. The results show that the use of starch from corn and maize (commercially available Hylon VII with maize, respectively) is the better combination to increase the mesopore volume. Moreover, “low-cost” mesoporous carbons have been obtained by the direct carbonization of the pre-treated starch mixtures with the IL. In all cases, the IL can be recovered and reused, as demonstrated by its recycling up to three times. Furthermore, and as a comparison, chitosan has been also used as a precursor to obtain N-doped mesoporous carbons (5.5 wt% N) with moderate mesoporosity (Vmeso = 0.43 cm3/g). The different mesoporous carbons have been tested as cathode components in Li-O2 batteries and it is shown that a higher carbon mesoporosity, produced from starch precursor, or the N-doping, produced from chitosan precursor, increase the final battery cell performance (specific capacity and cycling).

Template-Free Preparation of a Mesopore-Rich Hierarchically Porous Carbon Monolith from a Thermally Rearrangeable Polyurea Network

“…Carbon is critical in catalysis, energy storage and conversion, and molecular separation. Fabricating carbon with a hierarchical pore structure is essential for rapid molecular transport between the inner pore surface and the bulk medium [1][2][3][4][5][6]. The hierarchical pore structure consists of macropores (>50 nm), mesopores (2 nm < d < 50 nm), and micropores (<2 nm) that are three-dimensionally interconnected [7].…”

Polysaccharide Modified Cathodes for High-Capacity Rechargeable Nonaqueous Li–O2 Batteries

“…The higher p K a of glucose (having −OH functionalities) than those of water or alcohols makes it a suitable additive that does not undergo the above-mentioned side reactions. Even though the polysaccharides have been integrated for different electrochemical energy storage systems such as a binder in a Li–S battery or a protective film for Li dendrite suppression, to obtain the mesoporous carbon for electrodes in Li-ion/O 2 batteries, , etc., the influence of the functionalities in altering the discharge mechanism at the air-cathode of Li–O 2 batteries is explored for the first time in this report. The proposed glucose modification of the air-electrode is easy to implement via simple drop-casting followed by air-drying.…”