Matthieu Courty

Lithium Salt of Tetrahydroxybenzoquinone: Toward the Development of a Sustainable Li-Ion Battery

The use of lithiated redox organic molecules containing electrochemically active C=O functionalities, such as lithiated oxocarbon salts, is proposed. These represent alternative electrode materials to those used in current Li-ion battery technology that can be synthesized from renewable starting materials. The key material is the tetralithium salt of tetrahydroxybenzoquinone (Li(4)C(6)O(6)), which can be both reduced to Li(2)C(6)O(6) and oxidized to Li(6)C(6)O(6). In addition to being directly synthesized from tetrahydroxybenzoquinone by neutralization at room temperature, we demonstrate that this salt can readily be formed by the thermal disproportionation of Li(2)C(6)O(6) (dilithium rhodizonate phase) under an inert atmosphere. The Li(4)C(6)O(6) compound shows good electrochemical performance vs Li with a sustained reversibility of approximately 200 mAh g(-1) at an average potential of 1.8 V, allowing a Li-ion battery that cycles between Li(2)C(6)O(6) and Li(6)C(6)O(6) to be constructed.

In search of an optimized electrolyte for Na-ion batteries

Electrolytes are essential for the proper functioning of any battery technology and the emerging Na-ion technology is no exception. Hence, a major focus on battery research is to identify the most appropriate formulation so as to minimize interface reactions and enhance both cell performances and safety aspects. In order to identify suitable electrolyte formulations for Na-ion chemistry we benchmarked various electrolytes containing diverse solvent mixtures (cyclic, acyclic carbonates, glymes) and Na-based salts having either F-based or perchlorate anions and measured viscosity, ionic conductivity, and thermal and electrochemical stability. The binary EC:PC solvent mixture has emerged as the best solvent formulation and has been used to test the performance of Na/hard carbon cells with both NaClO4 and NaPF6 as dissolved salts. Hard carbon electrodes having reversible capacities of 200 mA h g−1 with decent rate capability and excellent capacity retention (>180 cycles) were demonstrated. Moreover, DSC heating curves demonstrated that fully sodiated hard carbon cycled in NaPF6–EC:PC exhibits the highest exothermic onset temperature and nearly the lowest enthalpy of reaction, thus making this electrolyte most attractive for the development of Na-ion batteries.

Lead-free Ba0.8Ca0.2(ZrxTi1−x)O3 ceramics with large electrocaloric effect

The electrocaloric effect was investigated in lead-free Zr doped Ba0.8Ca0.2(ZrxTi1−x)O3 (BCTZ) ceramics synthesized by a conventional sintering process. Room-temperature x-ray diffraction analysis showed that the tetragonal structure is obtained in BCTZ for x  ≤ 0.08 and a pseudo cubic phase for x > 0.08. The dielectric spectroscopy and calorimetry revealed that the Curie temperature decreases as a consequence of Zr doping and that the BCTZ exhibits a first order ferroelectric phase transition. The electrocaloric effect was determined by the calculation of the electrocaloric change of temperature (ΔT) using the Maxwell relation based on the P–E hysteresis loops measured at different temperatures. A large electrocaloric responsivity ΔT/ΔE = 0.34 × 10−6 Km/V was found for x = 0.04, which significantly exceeds of values found so far in other lead-free electrocaloric materials.

The effects of moderate thermal treatments under air on LiFePO 4-based nano powders

The thermal behavior under air of LiFePO4-based powders was investigated through the combination of several techniques such as temperature-controlled X-ray diffraction, thermogravimetric analysis and Mossbauer and NMR spectroscopies. The reactivity with air at moderate temperatures depends on the particle size and leads to progressive displacement of Fe from the core structure yielding nano-size Fe2O3 and highly defective, oxidized LixFeyPO4 compositions whose unit-cell volume decreases dramatically when the temperature is raised between 400 and 600 K. The novel LiFePO4-like compositions display new electrochemical reactivity when used as positive electrodes in Li batteries. Several redox phenomena between 3.4 V and 2.7 V vs.Li were discovered and followed by in-situX-ray diffraction, which revealed two distinct solid solution domains associated with highly anisotropic variations of the unit-cell constants.

A green Li–organic battery working as a fuel cell in case of emergency

The routine access to electricity always means a drastic change in terms of quality of life making it easier and safer. Consequently, the global electric demand both on and off-the-grid is growing and calls for ongoing innovation to promote reliable, clean and safe power supplies. In this context, the development of new chemistries for batteries and fuel cells could play a critical role. From our prospects aiming at fostering the concept of sustainable organic batteries, we report in this article on the peculiar properties of dilithium (2,5-dilithium-oxy)-terephthalate salt, a novel redox-active material. Based on an oriented retrosynthetic analysis, we have succeeded in elaborating this organic electrode material through an original and low-polluting synthesis scheme, which includes both chemical and biochemical CO2 sequestration in conjunction with a closed-loop solution for recycling products. Beyond its remarkable electrochemical performance vs. Li, especially as a lithiated cathode material, this compound behaves also like an oxygen scavenger. This dual electrochemical/chemical reactivity makes the self-recharging of a Li cell based on this organic salt possible by opening it to air ensuring an electrical power reserve when a conventional electrical recharge is not possible. In such a case, the pristine rechargeable Li–organic battery operates as a sort of “Li/O2 fuel cell”.

Improving the energy density of Na3V2(PO4)3-based positive electrodes through V/Al substitution

The crystal chemistry and the electrochemical properties upon Na+ extraction/insertion of NASICON-type Na3AlyV2−y(PO4)3 compositions (y = 0.1, 0.25 and 0.5) were investigated. It was found that this family of V/Al substituted NASICON materials undergoes multiple reversible phase transitions between −50 °C and 250 °C upon heating, from monoclinic to rhombohedral symmetry, related to progressive disordering of Na+ ions within the framework. Na+ insertion/extraction mechanisms were monitored by operando X-ray diffraction. It is shown for the first time that substitution of aluminum for vanadium in Na3Al0.5V1.5(PO4)3 increases significantly the theoretical energy density of these promising positive electrodes (425 W h kg−1) due to its lighter molecular weight and the possibility of reversible operation on the V4+/V5+ redox couple at 3.95 V vs. Na+/Na.

Fluorosulfate Positive Electrodes for Li-Ion Batteries Made via a Solid-State Dry Process.

Ionothermal synthesis has recently been used to prepare a fluorosulfate (LiFeSO 4 F) capable of reversibly intercalating Li at 3.6 V vs Li, making this material a serious contender to LiFePO 4 for HEV and electric vehicle applications. Although fluorosulfates are made from low cost and abundant starting materials, their synthesis is costly because of the use of ionic liquids as synthetic medium. Herein, we report a solid-state process by which LiFeSO 4 F can be synthesized without the use of ionic liquids but at the expense of both longer reaction time and weakly contaminated samples. Additionally, we show how powerful Mossbauer spectroscopy can be in the optimization of the various stages of electrode preparation as shown through the synthesis of LiFeSO 4 F and its implementation into an electrode. The importance of having Fe 3+ -free hydrated precursors to routinely obtain pure LiFeSO 4 F samples is shown together with the need to optimize ballmilling conditions to preserve Fe 3+ -free LiFeSO 4 F composites. Samples prepared via this low temperature solid-state process show battery performances approaching those of samples prepared using ionic liquids as synthetic medium. Furthermore, this process can be extended to the synthesis of the other members of the fluorosulfates AMSO 4 F family with A = Li, Na and M = Fe, Co, and Ni.

Tetrabutylammonium prolinate-based ionic liquids: a combined asymmetric catalysis, antimicrobial toxicity and biodegradation assessment

Chiral ionic liquids (CILs) tetrabutylammonium-(S)-prolinate, tetrabutylammonium-(R)-prolinate and tetrabutylammonium trans-4-hydroxy-(S)-prolinate were investigated as chiral additives in the Pd-catalyzed enantioselective hydrogenation of α,β-unsaturated ketones. These CILs were easily prepared in one step from the aminoacid and tetrabutylammonium hydroxide and characterized (NMR, IR, optical rotation, elemental analysis, DSC, viscosity, decomposition temperature). The research strategy was to assess the antimicrobial toxicity (>20 strains) and biodegradability (OECD 301D) of the CILs at the same time as undertaking the asymmetric catalysis study. The Pd-catalyzed enantioselective hydrogenation of the carbon–carbon double bond of α,β-unsaturated ketones under mild conditions (room temperature, 1 atm of H2) in different solvents with CILs present. The best results were obtained in i-PrOH after 18 hours of reaction with a i-PrOH/IL ratio of 5. While all three CILs have low antimicrobial toxicity to a wide range of bacteria and fungi, tetrabutylammonium-(S)-prolinate, tetrabutylammonium-(R)-prolinate and tetrabutylammonium trans-4-hydroxy-(S)-prolinate did not pass the Closed Bottle biodegradation test.

On the nature of phase transitions in the tetragonal tungsten bronze GdK2Nb5O15 ceramics

Phase transitions in gadolinium potassium niobate GdK2Nb5O15 (GKN) ceramics have been investigated by x-ray diffraction, dielectric susceptibility, differential scanning calorimetry, and Raman scattering. The results of our complementary studies show that GKN exhibits two phase transitions at Tc1 = 238 °C and Tc2 = 375 °C attributed to the ferroelectric-antiferroelectric-paraelectric (FE-AFE-PE) phase transitions. According to the x-ray diffraction analysis, the FE and PE phases were refined in the polar P4bm and centrosymmetric P4/mbm space groups. For the intermediate phase, the structure is refined in the space group P4nc with doubling of the c unit cell parameter, which is compatible with an AFE phase. This result was confirmed by Raman spectroscopy since new low-frequency lines are activated in the AFE phase due to the Brillouin zone-folding effect, typical for the modulated phases. The presence of the AFE phase between the FE and PE phases and the complex nature of tetragonal tungsten bronze crystal...

An Oxysulfate Fe2O(SO4)2 Electrode for Sustainable Li-Based Batteries

High-performing Fe-based electrodes for Li-based batteries are eagerly pursued because of the abundance and environmental benignity of iron, with especially great interest in polyanionic compounds because of their flexibility in tuning the Fe(3+)/Fe(2+) redox potential. We report herein the synthesis and structure of a new Fe-based oxysulfate phase, Fe2O(SO4)2, made at low temperature from abundant elements, which electrochemically reacts with nearly 1.6 Li atoms at an average voltage of 3.0 V versus Li(+)/Li, leading to a sustained reversible capacity of ≈125 mAh/g. The Li insertion-deinsertion process, the first ever reported in any oxysulfate, entails complex phase transformations associated with the position of iron within the FeO6 octahedra. This finding opens a new path worth exploring in the quest for new positive electrode materials.