Barbara Laïk

High-Rate Capability Silicon Decorated Vertically Aligned Carbon Nanotubes for Li-Ion Batteries

The concept of a hybrid nanostructured collector made of thin vertically aligned carbon nanotubes (CNTs) decorated with Si nanoparticles provides high power density anodes in lithium-ion batteries. An impressive rate capability is achieved due to the efficient electronic conduction of CNTs combined with well defined electroactive Si nanoparticles: capacities of 3000 mAh g−1 at 1.3C and 800 mAh g−1 at 15C are achieved.

Ion–ion interactions and lithium stability in a crosslinked PEO containing lithium salts

Abstract The electrochemical properties of a solid polymer electrolyte prepared by chemical crosslinking of PEO 2000 and containing LiAsF 6 or LiCF 3 SO 3 were investigated for electrochemical window, lithium stability and lithium/electrolyte interface stability. FTIR spectroscopy of the salt anion (AsF 6 − and CF 3 SO 3 − ) was also used to determine the nature and the extent of ion pairing and ion aggregation in these crosslinked electrolytes. The lithium corrosion appears as a diffusion limited process as the coulombic efficiency of a lithium deposit decreases with the square root of the contact time of lithium with the crosslinked PEO. Impedance parameters are consistent with an increase of the passivating layer upon storage. Their values strongly differ with the salt anion.

Influence of lithium salts on the behaviour of a petroleum coke in organic carbonate solutions

Abstract We studied the influence of the anion of lithium salts dissolved in a solution based on propylene carbonate (PC), ethylene carbonate (EC) and dimethyl carbonate (DMC) on the electrochemical properties of a petroleum coke (LONZA) and on the petroleum coke/electrolyte interface. We explored a correlation between the electrochemical properties and the surface chemistry of this coke using infrared spectroscopy, Rutherford backscattering spectrometry, fluoride selective electrode and standard electrochemical techniques. The different techniques show that LiF is a major product of the reduction of LiAsF 6 and LiBF 4 and a minor product of the reduction of LiCF 3 SO 3 and LiTFSI. Alkyl carbonates are generated by reductions of the carbonate solvents to an extent which is independent of the anion of the lithium salt. Electrochemical behaviour of the coke is discussed with regard to the composition of the passivating layer. We found better cycling behaviour and greater lithium stability with LiCF 3 SO 3 and LiTFSI.

Two anode materials for Li ion batteries with different reaction mechanisms : silicon nanowires and ruthenium nitride thin film

Research carried out in our laboratory is devoted to new materials of electrodes for lithium ion batteries. This presentation focuses on anodic materials, especially on two examples, silicon and ruthenium nitride. In both cases, electrochemical properties and structural evolutions are correlated in order to optimize performances in terms of specific capacity, cyclability and rate capability.