High electronic conductivity in nanostructured materials based on lithium-iron-vanadate-phosphate glasses

Highly conductive cathode materials for Li-ion batteries prepared by thermal nanocrystallization of selected oxide glasses

“…Our experience with that method has shown that one can, by the appropriately chosen heat-treatment conditions, achieve a huge (even by a factor 10 9 ) and irreversible conductivity enhancement. We have also shown that this effect is closely related to changes in the microstructure -namely to appearance of nanoscale crystalline grains, with dimensions going down even to a few nanometers, embedded in the glassy matrix [18]. Taking into account this correlation we have postulated that the conductivity enhancement is caused mainly by the presence of interfacial regions around newly formed nanograins.…”

“…In recent years, we have proposed and investigated an alternative route to the conductivity enhancement, namely a thermal nanocrystallization of glassy analogs of the important crystalline cathode materials, such as: V 2 O 5 [15,16], LiFePO 4 [17,18] and Li 3 V 2 (PO 4 ) 2 F 3 [19]. The advantages of our approach to produce active cathode materials include the absence of carbon additives and simplicity and straightforwardness of synthesis, which consists of two stages only: (i) glass preparation by melt-quenching and (ii) thermal treatment of the glass to induce its nanocrystallization.…”

“…Appropriate amounts of precursors: Li 2 CO 3 (Aldrich, 99.9%), FeC 2 O 4 ·2H 2 O (Aldrich, 99.9%), (NH 4 )H 2 PO 4 (POCh -Polish Chemicals, 99.5%) and V 2 O 5 (Aldrich, 99.6%) were mixed in a mortar and annealed under flow of nitrogen (purity 99.999%) in two steps: (i) at 300 • C for 2 h and (ii) at 570 • C for next 2 h. Subsequent stages of the synthesis of the glassy materials involved second mixing in a mortar, melting at 1250 • C and a rapid quenching, according to the procedure described in more detail in our earlier paper [18].…”

Influence of tin ions on AC conductivity and dielectric features of Li2O–PbO–P2O5 glass system

“…This band may also be considered as an overlapping band due to P=O stretching vibrations and due to PO 2− groups. Conventional band due to symmetric stretching vibrations of PO 4 3− units is observed at about 1090 cm −1 . A prominent band considered to be at 780 cm −1 due to P-O-P symmetric stretching vibrations and or due to the vibrations of pyrophosphate groups (P 2 O 7 4− ) is also located in the spectra.…”

“…These materials possess superior physical properties, for instance, high thermal expansion coefficients, low melting and softening temperatures, and high ultraviolet (UV) and far-infrared (IR) transmission [2][3][4]. Mixed electronic and ionic, pure electronic or pure ionic conduction is expected in these glasses depending upon the composition of the glass constituents.…”