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In this work, we examine the Mg-ion desolvation and intercalation process at the Chevrel phase Mo 6 S 8 cathode surface from first-principles. It is reported that in electrolytes based on chlorides in tetrahydrofuran (THF), Mg 2+ is strongly coordinated by the counterion Cl and can form singly charged MgCl + and Mg 2 Cl + 3 species in solution. During cell discharge, Mg intercalation into the Chevrel phase requires breaking the strong, ionic Mg-Cl bond. Our simulation results indicate that the stripping of Cl is facilitated by the existence of another cationic species, Mo on the Chevrel phase surface. Once Mg is intercalated, it leaves the counterion, Cl , on the surface, bound to Mo. It is found that the chlorinated surface presents higher activation barriers to further intercalate Mg. Instead, the chlorinated surface continues to interact with incoming MgCl + species and form various MgCl y surface adsorbates. With certain energy costs, the neutral MgCl 2 unit may be released from these surface adsorbates to reopen Mo sites on the surface and permit continuous Mg intercalation. Presuming compatibility of chloride electrolytes with the Mg metal anode, our work implies that finding a compatible cathode material will depend critically on its ability to catalyze Mg-Cl bond-breaking. This may explain the success of the Chevrel phase, with its open Mo sites, permitting intercalation of Mg from the halide solutions, whereas higher voltage transition metal oxides, which typically lack open metal sites, require more weakly coordinating anions in their electrolytes.

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The polymer-composite binder used in lithium-ion battery electrodes must both hold the electrodes together and augment their electrical conductivity while subjected to mechanical stresses caused by active material volume changes due to lithiation and delithiation. We have discovered that cyclic mechanical stresses cause significant degradation in the binder electrical conductivity. After just 160 mechanical cycles, the conductivity of polyvinylidene fluoride (PVDF):carbon black binder dropped between 45-75%. This degradation in binder conductivity has been shown to be quite general, occurring over a range of carbon black concentrations, with and without absorbed electrolyte solvent and for different polymer manufacturers. Mechanical cycling of lithium cobalt oxide (LiCoO 2 ) cathodes caused a similar degradation, reducing the effective electrical conductivity by 30-40%. Mesoscale simulations on a reconstructed experimental cathode geometry predicted the binder conductivity degradation will have a proportional impact on cathode electrical conductivity, in qualitative agreement with the experimental measurements. Finally, ohmic resistance measurements were made on complete batteries. Direct comparisons between electrochemical cycling and mechanical cycling show consistent trends in the conductivity decline. This evidence supports a new mechanism for performance decline of rechargeable lithium-ion batteries during operation -electrochemically-induced mechanical stresses that degrade binder conductivity, increasing the internal resistance of the battery with cycling. Lithium-ion batteries (LIB) are an enabling energy storage technology for portable consumer electronics, electric vehicles and renewable power generation in part due to their high energy densities. The energy density is driven by not only the relatively large potential of lithium-ion chemistries, but also the ability of active materials to store large amounts of lithium.1 The most common graphitic carbon anode can absorb up to one lithium for every carbon atom. Recent research on higher capacity anodes such as silicon has highlighted an increased need for understanding the mechanics of lithium-ion batteries. As the lithium is shuttled between the anode and cathode, the active materials expand and contract to accommodate the lithium. The resulting volume changes are accentuated for high capacity materials such as silicon which can increase in volume by up to 400% during lithiation. 2Because most LIB electrodes are porous multicomponent composites, understanding the generation and impact of mechanical stresses on batteries can be difficult. The electrode is generally 50-75 vol% solid fraction with active material consisting of micron-sized particles held together by an active binder, which is itself a composite of conductive carbon particles and polymer. The performance of the battery is highly dependent on this complex structure which must allow efficient ion and electron transport through the electrode. The void space in the porous structure allows lith...

The direct bioelectrocatalysis was demonstrated for pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-dependent GDH) covalently attached to single-walled carbon nanotubes (SWNTs). The homogeneous ink-like SWNT suspension was used for both creating the SWNT network on the microelectrode carbon surface and for enzyme immobilization. Functionalization of the SWNT surface by forming active ester groups was found to considerably enhance SWNT solubility in water with a range from 0.1 to 1.0 mg/mL. The PQQ-dependent GDH immobilized on the surface of the SWNTs exhibited fast heterogeneous electron transfer with a rate constant of 3.6 s À1 . Moreover, the immobilized PQQ-dependent GDH retained its enzymatic activity for glucose oxidation. A fusion of PQQ-dependent GDH with SWNTs has a great potential for the development of low-cost and reagentless glucose sensors and biofuel cells.

By utilizing an equilibrium processing strategy that enables co-firing of oxides and base metals, a means to integrate the lithium-stable fast lithium-ion conductor lanthanum lithium tantalate directly with a thin copper foil current collector appropriate for a solid-state battery is presented. This resulting thin-film electrolyte possesses a room temperature lithium-ion conductivity of 1.5 × 10(-5) S cm(-1) , which has the potential to increase the power of a solid-state battery over current state of the art.

The chemical reactivity of silicon surface species with LiPF6/carbonate electrolyte are detailed via FTIR spectroscopy and verified by MD/DFPD simulations.

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