Role of Electrochemically Driven Cu Nanograins in CuGa₂ Electrode

Abstract

Upon lithiation, the active (Ga) and inactive component (Cu) in a binary intermetallic CuGa 2 electrode are converted to nanograins (<50 nm) of Li x Ga and metallic Cu, respectively. It was found that the Cu nanograins are not idling as an inactive ingredient but have a strong influence on the thermodynamic and kinetic properties of Li x Ga phases through a partial bonding to Ga atoms of Li x Ga (CufGa-Li). The Li x Ga phase diagram is altered by the presence of Cu nanograins, eloquently demonstrating that the surface energy becomes more important than internal energy in controlling thermodynamics of nanosized materials. The lithiation rate is slower than that for pure Ga electrode because of activation energy needed for bond cleavage of the partial bonding. The delithiation rate capability is, however, exceptionally good; the capacity at 26 C amounts to 91% of that at 0.13 C, which is indebted to a weakening in the Ga-Li bond by the CufGa partial bonding.

Electrochemical stability of bis(trifluoromethanesulfonyl)imide-based ionic liquids at elevated temperature as a solvent for a titanium oxide bronze electrode

“…The C 1s spectra clearly show that the organic carbonates are also decomposed. The C 1s spectra deconvolute to five peaks: graphitic carbons at 284 eV, C-C/C-H at 285 eV, C-N/C-OH at 286 eV, ester at 287 eV, CO 3 2− /CF 2 at 290.0-290.5 eV, and CF 3 at 293 eV [27][28][29]. The most revealing feature is that the C 1s photoelectrons emitted from the CO 3 2− /CF 2 groups at 290.0-290.5 eV are much more abundant for the EC:DEC solvent than for the EMI-based ionic liquid.…”

“…The C 1s spectra deconvolute to five peaks: graphitic carbons at 284 eV, C-C/C-H at 285 eV, C-N/C-OH at 286 eV, ester at 287 eV, CO 3 2− /CF 2 at 290.0-290.5 eV, and CF 3 at 293 eV [27][28][29]. The most revealing feature is that the C 1s photoelectrons emitted from the CO 3 2− /CF 2 groups at 290.0-290.5 eV are much more abundant for the EC:DEC solvent than for the EMI-based ionic liquid. Given that the photoelectrons from the CF 2 moiety that may come from PVdF binder can be neglected due to thick film deposition on these electrodes, the peak at 290.0-290.5 eV is mainly associated with CO 3 2− groups that are derived from the organic carbonates (EC:DEC).…”

“…The most revealing feature is that the C 1s photoelectrons emitted from the CO 3 2− /CF 2 groups at 290.0-290.5 eV are much more abundant for the EC:DEC solvent than for the EMI-based ionic liquid. Given that the photoelectrons from the CF 2 moiety that may come from PVdF binder can be neglected due to thick film deposition on these electrodes, the peak at 290.0-290.5 eV is mainly associated with CO 3 2− groups that are derived from the organic carbonates (EC:DEC). Also note that an intense peak at 284 eV is observed with the initial TiO 2 -B electrode, which must come from the carbon additive (Super-P).…”

“…Recently, the issues of oil price and global warming have brought an increasing awareness to the need for more fuel-efficient and less-polluting hybrid electric vehicles (HEVs), for which LIBs are being considered as replacements for the present nickel-metal hydride cells [1][2][3]. The performance of LIBs, however, still falls short of the requirements for many transportation applications with respect to specific energy, specific power, cell life, and safety characteristics.…”

High‐Capacity Anode Materials for Lithium‐Ion Batteries: Choice of Elements and Structures for Active Particles

“…Lithiation/delithiation of Ga near room temperature proceeds via the reversible formation of crystalline phases in the order Ga↔Li 2 Ga 7 ↔LiGa↔Li 2 Ga . Ga alloys with Cu, which improves the delithiation rate, but reduces the lithiation rate . Studies attempting to assemble a conventional electrode with Ga have prelithiated[142b] or encapsulated it in carbon,[] but have yet to show high‐capacity stable cycling.…”