Performances of lithium-ion cells constituted of NMC // LTO electrodes and ionic liquid or carbonates-based electrolytes

CAPLUS AN 2016:1713716(Journal; Online Computer File)International audienceCom. lithium-ion batteries could lead to safety issues related to the use of flammable carbonates as electrolyte solvents. To provide safer cells, ionic liqs. are widely studied as they possess negligible vapor pressure and reduced flammability. This paper presents a comparison between carbonates and ionic liq.-based electrolytes, comprising bis(trifluoromethanesulfonyl)imide [NTf2] anion and imidazolium [Im] or pyrrolidinium [PYR] cations. Lithium-ion cells constituted of Li4Ti5O12 (LTO) and LiNi1/3Mn1/3Co1/3O2 (NMC) electrodes were assembled and cycled at 25 and 60°C with these different electrolytes. These systems were investigated by cyclic voltammetry (CV) and electrochem. cycling. Diffusion coeffs. of lithium ions were also detd. by CV techniques and by liq. NMR. [on SciFinder(R)

Characterization of LTO//NMC Batteries Containing Ionic Liquid or Carbonate Electrolytes after Cycling and Overcharge

CAPLUS AN 2015:510771(Journal; Online Computer File)International audienceElectrochem. stabilities under cycling and overcharge of Li4Ti5O12 (LTO)//LiNi1/3Mn1/3Co1/3O2 (NMC) batteries with two ionic liq.-based electrolytes and a com. electrolyte were investigated at 25 and 60°. The electrolytes were constituted of ethylene carbonate/di-Me carbonate mixts. with LiPF6, and of imidazolium and pyrrolidinium-based ionic liqs. contg. the bis(trifluoromethanesulfonyl)imide anion (NTf2) assocd. to LiNTf2 salt. The expts. were performed in coin and pouch cells in order to follow the evolution of the stability of both solid, liq., and gas phases. The decompn. products and stability of the electrolytes was assessed by gas chromatog. coupled with IR spectroscopy. The characterization of the electrode surfaces by SEM, XRD, and XPS techniques was reported, after cycling and overcharge. The XPS anal. of both electrodes indicated that their surfaces were covered by an IL film in the case of NMC, and by several NTf2 anion decompn. products in the case of LTO. This work highlights the difference between thermal and electrochem. stability, esp. for imidazolium-based electrolytes. [on SciFinder(R)

Functionalized Carbon Nanotubes for Lithium-Organic Batteries

International audienceLithium batteries are among the most promising systems for electrochemical energy storage. However, their capacity and cost-efficiency have to be improved for further applications.1 Lithium/organic batteries offer an interesting alternative to the classical Li-ion systems due to the low molecular weight of organic materials, their potential low cost and recyclability. However, two major roadblocks currently prevent the industrial development in these kind of batteries: (i) the progressive dissolution of the active material in the electrolyte, which hinders the cyclability of the devices and (ii) the electrical insulating nature of organic materials.2Here, we develop a new positive electrode material avoiding the dissolution of the active material in the electrolyte upon cycling, by grafting new diazonium derivatives containing active groups onto multi-walled carbon nanotubes (MWNTs) at different ratios between the carbon nanotubes and the active material.3 The MWNTs insure a well distributed electronic conductivity inside the positive electrode and serve as a support for a covalent immobilization of the organic active species

Nuclear microanalysis of lithium dispersion in LiFePO4 based cathode materials for Li-ion batteries

International audienc

A New Conducting Copolymer Bearing Electro‐Active Nitroxide Groups as Organic Electrode Materials for Batteries

International audienceAbstract To reduce the amount of conducting additives generally required for polynitroxide‐based electrodes, a stable radical (TEMPO) is combined with a conductive copolymer backbone consisting of 2,7‐bisthiophene carbazole (2,7‐BTC), which is characterized by a high intrinsic electronic conductivity. This work deals with the synthesis of this new polymer functionalized by a redox nitroxide. Fine structural characterization using electron paramagnetic resonance (EPR) techniques established that: 1) the nitroxide radicals are properly attached to the radical chain (continuous wave EPR) and 2) the polymer chain has very rigid conformations leading to a set of well‐defined distances between first neighboring pairs of nitroxides (pulsed EPR). The redox group combined with the electroactive polymer showed not only a very high electrochemical reversibility but also a perfect match of redox potentials between the de‐/doping reaction of the bisthiophene carbazole backbone and the redox activity of the nitroxide radical. This new organic electrode shows a stable capacity (about 60 mAh g −1 ) and enables a strong reduction in the amount of carbon additive due to the conducting‐polymer skeleton

Influence of the self-organization of ionic liquids on the size of ruthenium nanoparticles: Effect of the temperature and stirring

The size of ruthenium nanoparticles is governed by the degree of self-organization of imidazolium based ionic liquid in which they are generated from (ƞ4-1,5-cyclooctadiene)(ƞ6-1,3,5-cyclooctatriene)ruthenium : the most structured the ionic liquid, the smallest the size