Frédéric Sauvage

Room-Temperature Synthesis Leading to Nanocrystalline Ag2V4O11

This work highlights a room-temperature composition study of the Ag(2)O/V(2)O(5)/HF((aq)) ternary system, leading to the precipitation of either various silver vanadates having Ag/V ratios from 1/2 to 3/1 or the new silver vanadium oxyfluoride compounds Ag(4)V(2)O(6)F(2) and Ag(3)VO(2)F(4), and a synthetic procedure that affords nanocrystalline Ag(2)V(4)O(11) (SVO) at room temperature. The as-precipitated SVO particles exhibit an acicular morphology, 10-15 x 50-200 nm in size, and present a peculiar reactivity vs lithium notably through a Ag(+)/Li(+) displacement reaction that progresses in a reversible fashion. This step forward thus enables the reversible and simultaneous combination of two active redox processes (silver and vanadium), providing a significant enhancement in the cathode gravimetric capacity of 320 mAh/g at C rate and more than 250 mAh/g at 5C.

Ag4V2O6F2 (SVOF): a high silver density phase and potential new cathode material for implantable cardioverter defibrillators.

The electrochemical reactivity of the cathode material Ag 4V 2O 6F 2 (SVOF) versus lithium, with a particular emphasis on the lithium insertion mechanism, was studied by means of the complementary techniques in situ X-ray diffraction, electron paramagnetic resonance, and high-resolution transmisssion electron microscopy. This study confirms the initial reports of a high capacity for SVOF of 148 mAh/g above 3 V and that the reduction of silver above 3 V (vs Li (+)/Li (0)) leads to a loss of SVOF crystallinity until it becomes completely amorphous between the third and fourth lithiums inserted. Next, vanadium is reduced between 2.5 and 1.5 V (vs Li (+)/Li (0)) for the fifth and sixth lithiums inserted. In addition, the polarization within the cathode is significantly lower for the vanadium reduction than for the silver reduction. The silver metal morphologies consisted of nanoparticles ( approximately 5 nm diameter) and dendrites and were both seen in samples of lithiated SVOF.

Ag 6Mo 2O 7F 3Cl: A new silver cathode material for enhanced ICD primary lithium batteries

As a potential cathode material for the ICD lithium battery, one advantage of Ag(6)Mo(2)O(7)F(3)Cl (SMOFC) is its enhanced gravimetric capacity of ca. 133 mAh/g above 3 V (vs Li(+)/Li) delivered by two biphasic transitions at 3.46 and 3.39 V (vs Li(+)/Li). The unique crystal structure of SMOFC enables a high silver ion conduction: sigma( perpendicular[001]) = 3.10(-2) S/cm (+/-2.10(-2) S/cm) and sigma(//[001]) = 4.10(-3) S/cm (+/-2.10(-3) S/cm) and, hence, an excellent discharge rate capability. Lithium insertion has been monitored by in situ XRD measurements with HRTEM investigations. There is a linear isotropic collapse of the structure leading to a fully amorphous structure beyond four inserted lithiums.