Effect of Carbon Additives on the Electrochemical Properties of  AB 5 Graphite Composite Electrodes Prepared by Mechanical Milling

Abstract

The effect of mechanical milling on powder mixtures consisting of graphite and AB5 alloys, prepared either by mechanical alloying or by a high‐temperature melting process, has been investigated. The resulting hydride‐forming composite electrodes show a 10 and 40% capacity enhancement for arc‐melted and mechanically prepared AB5 alloys, respectively. Such an increase in capacity is suggested to be the result of several cumulative effects: (1) a mechanically induced reducing role of graphite which eliminates the AB5 particles of oxide coatings, enabling a better hydrogen adsorption/absorption and diffusion into the insertion sites of the alloy, (2) the appearance of an increasingly important double‐layer capacitance on each particle with increased milling time that adds to the faradic component, and (3) the improved electronic conductivity between the active AB5 material and the graphite that allows a better utilization of the alloy. © 1999 The Electrochemical Society. All rights reserved.

Metal hydrides: an innovative and challenging conversion reaction anode for lithium-ion batteries

“…In addition, the carbon also acts as conductive additive and a coating agent, which prevents the agglomeration of the hydride particles during grinding. A detailed study of the effect of mechanical milling on the physical/chemical and electrochemical properties compared to AB 5 alloys is available in [ 34 ].…”

“…The degree of disorder for carbonaceous materials increases with increased milling time and is proportional to the d (002) distance, as previously established [ 35 – 36 ]. Note that the C-free bonds created during the fracture of the graphene layer serve as oxygen scavengers, and their agglomeration and coating of the alloy particles enable a better chemical/physical protection against oxidation [ 34 ].…”

“…Based on the milling behavior of carbonaceous material [ 34 – 35 ], MgH 2 is ground using a carbon having the maximum BET surface area in order to agglomerate carbon particles on MgH 2 particles. DSC traces of MgH 2 –10% C t , z composite obtained after 4 h of grinding shows a decrease of 48 °C of the desorption peak maximum of hydride carbon composite compared to the commercial hydride, as expected ( Fig.…”

An Overview of Hydrogen Generation and Storage for Low-Temperature PEM Fuel Cells

“…Others have tried mechanical milling and graphite additives with AB 5 -type alloys and have also found capacity increases up to 40 percent [22]. Three cumulative effects have been suggested: (1) graphite acts as a reducing agent to prevent oxide coatings on the AB 5 alloy, permitting better H 2 diffusion, adsorption, and desorption; (2) double-layer capacitance increases with milling time and adds to the faradaic component; and (3) improved electronic conductivity between the alloy and graphite allows better utilization of the alloy [22].…”

Theoretical Approach Towards the Understanding of Asymmetric Additions of Dialkylzinc to Enals and Iminals Catalysed by [2.2]Paracyclophane‐Based N,O‐Ligands

“…2 The electroactive materials must be electrochemically addressable for their capacity to be explored fully. However, owing to a lack of electronic conductivity of the electrode material, a large amount of conducting additive, such as carbon black, has to incorporated into the electrode sheet to form a continuous conducting network for electron percolation 3. 4 Consequently, the energy density of the battery is greatly decreased by the presence of a large volume of inactive conducting agent.…”