No abstract

We present a detailed study on graphene-coated aluminum thin films for Li-ion battery anode applications. The best electrode ageing behavior is obtained for Al films encapsulated with four porous graphene layers. Graphene encapsulation prevents "crushed" Al nanoparticles from detaching from the anode, thus allowing prolonged charge-discharge cycling. Graphene also provides surface conduction paths for electrons as well as diffusion paths for Li atoms. For the first time, we report the electrochemical room temperature formation of phases such as LiAl and even LiAl, with a higher Li content than β-LiAl. More interestingly, we observe a progressive change of the composite thin film electrode, switching from a pure galvanic to a pseudocapacitive behavior as the size of the Al grains decreases from ∼100 to 5-10 nm due to repeated Li alloying-dealloying. The capacity values of ∼900 and 780 mAh/g are obtained after, respectively, 500 and 1000 charge-discharge cycles at 0.1C. Our results may refocus the interest of the battery community on Al-based thin film anodes, since they are potentially very simple to fabricate, particularly if porous graphene is replaced in the future by reduced graphite oxide.

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The preferential adsorption of ethane over ethylene would significantly simplify the overall ethane-ethylene separation scheme for ethylene purification. Ethane-selective adsorbents are still lacking compared to ethylene-selective adsorbents. We discovered that a fluorinated Metal-Organic Framework, FMOF-2, exhibits preferential adsorption of ethane over ethylene at pressures in the range of 40 kPa with ideal adsorbed solution theory selectivity of 3.3. The material was characterized by X-ray diffraction, argon physisorption at 87 K, thermal gravimetric analysis, scanning electron microscope (SEM) image, and Xray photoelectron analysis. Exposed fluorine functional groups on a porous material produced via a hydrogen-bonding type electrostatic attraction are thought to serve as ethane adsorption sites.