Neutron scattering measurements have played important roles in not only the structural information study, but also the dynamical insight of solid state ionic materials in the form of polymer, ...crystalline and glassy materials. Quasielastic neutron scattering (QENS) measurement explores the diffusion mechanism of mobile ions, on the other hand, inelastic neutron scattering (INS) reveals the dynamical insight of solid ionic conductor materials. Here we present the neutron scattering study of superionic glass (LiI)0.3(LiPO3)0.7 by using the inelastic neutron spectrometer AMATERAS at the Japan Proton Accelerator Research Complex (J-PARC). Simultaneous two dimensional maps of dynamical structure factor S(Q,E) with the incident energy Ei 93.85, 23.59, 10.57 and 5.92meV over a wide momentum transfer (Q)-range were observed for (LiI)0.3(LiPO3)0.7. The first sharp diffraction peak appears at Q ~1.8Å−1 in the elastic structure factor. From the inelastic scattering, low energy excitation or the Boson Peak appears at ~6.0–7.0meV. The extra quasielastic scattering was observed in the energy range 1meV<E<3meV at 285K but not at 20K. The Q dependence of the dynamical structure factor S(Q,E) can be approximated to the long-wave acoustic like density fluctuation.
The researches on solid electrolyte have been significantly increasing due to the safety problem in lithium ion battery. The lithium phosphates are chosen due to environmentally friendly. In the ...present study Li4P2O7 was synthesized by solid state reaction using NH4H2PO4 and Li2CO3 with the ratio 1:2 at various temperatures of 600 °C, 800 °C and 900 °C. The products were characterized by x-ray diffraction, scanning electron microscopy and impedance spectroscopy. The x-ray diffraction showed that all samples consisted of two phases. It was found that the products consisted of 52.44% Li4P2O7 and 47.56% LiPO3; 93.56% Li4P2O7 and 6.44% Li3PO4; and 46.27% Li4P2O7 and 53.67% Li3PO4 under the synthesizing temperature of 600 °C, 800 °C and 900 °C, respectively. The highest ionic conductivity of 3.85 × 10−5 S/m was achieved for composite Li4P2O7–Li3PO4 with the highest content of 93.56% Li4P2O7. This conductivity is higher compared with single phase of LiPO3, Li3PO4 and Li4P2O7. The increase in ionic conductivity may be due to the mixed anion effects related to the phosphate networks, and it also corresponds to the existence of anorthic phase Li4P2O7 with the space group P −1 (2). The crystal lattice analysis showed that the reactant Li4P2O7 consisted of diphosphate groups P2O7. The lithium tetrahedral LiO4 were linked to P2O7 groups formed a continuous framework containing large voids, available for Li+ ion transport, and thus it exhibited high conductivity. A composite Li4P2O7–Li3PO4 is a promising solid electrolyte for solid state battery.
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•The researches on solid electrolyte in lithium ion battery have been significantly increasing due to the safety problem.•Li4P2O7 was synthesized by solid state reaction using NH4H2PO4 and Li2CO3 with the ratio 1:2 at various temperatures of 600 oC, 800 oC and 900 oC..•The composite consisted of two phases, with best product contains 93.56% Li4P2O7 and 6.44% Li3PO4 synthesized at 800 oC.•The best ionic conductivity is 3.85 x 10-5 S/m achieved for composite Li4P2O7-Li3PO4 containing 93.56% Li4P2O7.•The high conductivity was due to the linked of LiO4 to P2O7 groups containing large voids, available for Li+ ion transport.
Phosphate‐based lithium materials, such as lithium iron phosphate (known as lithium ferrophosphate, LiFePO4, LFP), are among the safest materials for large‐scale lithium‐ion batteries due to the ...stability of the phosphate‐bound oxygen at elevated temperatures. LFP can be melt‐synthesized where the kinetics is faster, allowing for coarser and lower cost reactants. The most common lithium‐ and phosphate‐bearing reactants can react violently upon heat‐up and release a large volume of gaseous by‐product. Lithium metaphosphate (LiPO3, LPO) can improve the processability and safety of the operation. In this work, we investigate the thermal decomposition of lithium dihydrogenphosphate (LiH2PO4, LHP) to LPO up to 400 °C. The decomposition was analyzed by isothermal and constant rate differential thermogravimetric (DTG) experiments. Activation energy profiles were estimated by an isoconversional model‐free approach and kinetic model fitting. Li5H4P5O17 (L2.5) was determined to be the most stable reaction intermediate and can be isolated at temperatures between 200 and 240 °C. The resulting reaction is comprised of 6 reactions, where the LHP is progressively polymerized by condensation reactions leading successively to L2.5, Li3H2P3O10 (L3), Li4H2P4O13 (L4), and LPO. The first reaction step (LHP → L2.5) was fitted with 3 reactions series/parallel describing the solid surface reaction, the viscous/liquid surface reaction, and the bulk reaction. Limiting the reaction temperature to 400 °C results in a solid product that can be advantageous if LPO is to be prepared in advance and dosed for LFP synthesis.
Lithium dihydrogenphosphate (LHP) needs to be dehydrated to be safely applied for the melt casting process to produce lithium iron phosphate (LFP). The dehydration reaction consists of several ...consecutive melting, oligomerization, and crystallization steps resulting in a solid product stuck to the reaction vessel at around 400°C. Here we applied an electrical shell‐heated rotary kiln containing grinding media (ball‐mill rotary‐kiln, BaMRoK) to dehydrate LHP at 400°C and recover the ground product without needing any extra processing. The bulk convective heat transfer coefficient of the kiln has been calculated in the presence of the grinding media and the temperature profile has been modelled using COMSOL Multiphysics. The kinetic model of the reaction from thermogravimetric analysis (TGA) and the thermal profile suggest that the dehydration reaction mostly happens on the internal surface of the BaMRoK wall.
xAgI–(1−x)LiPO3 composite glass electrolytes were prepared by melt quenching technique by using a twin roller assembly operated at 2000rpm. The composite glasses with x<0.2 were completely amorphous. ...However, in glasses with x>0.2, micron size cluster particles of γ-AgI nanocrystallytes, embedded in a glass matrix were observed. This was confirmed by XRD and SEM studies. The conductivity of composite glasses increased by several orders of magnitude in comparison to pure LiPO3 glasses. Maximum conductivity of ~10−3S/cm was found for x=0.5 composition. FTIR studies suggest that AgI acts as a plasticizing agent which reduces the polymeric chain lengths of phosphate glasses. In addition AgI provides silver ions which contribute to the total ionic conductivity. It was shown by using Summerfield scaling that glasses with x<0.2 are mixed ion conducting with lithium and silver and both are contributing to the total conductivity. Summerfield scaling was not obeyed by these compositions. However glasses with x>0.2 obeyed the Summerfield scaling and it was deduced that in these glasses the conduction is predominantly due to silver ions and any conduction due to lithium ions if at all is negligible. Nearly constant loss (NCL) effects were observed in low AgI (x<0.2) glasses at low temperatures.
However no NCL effect was found in high AgI content glasses. It is expected that the presence of NCL is due to lithium ions only as NCL has been found in pure LiPO3.
► The dc conductivity increased by 6 orders in xAgI-(1-x) LiPO3 composite glasses for x=0.5with value of ~10–3S/cm. ► The enhancement in conductivity was attributed to highly mobile silver ions. ► For x<0.2 a mixed ion conduction due to lithium as well as silver ions was observed. ► For glasses with x<0.2 Summerfield scaling was not obeyed due to mixed ion conduction. ► Higher AgI glasses with x>0.2 showed ionic conduction due to silver ions only.
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