Eisuke Sugimoto

Ionic Conductivity of Solid Electrolytes Based on Lithium Titanium Phosphate

Solid electrolytes based on lithium titanium phosphate were prepared, and their phase, porosity of the sintered pellets, and electrical conductivity were studied. The conductivity was increased and the porosity decreased greatly by partially replacing Ti4+ and P5+ in with M3+ and Si4+ions, respectively. The maximum conductivity at 298 K is for . The conductivity was considerably increased by the mixing of binders such as or with . The main reason for the conductivity enhancement of these electrolytes seems to be attributable to the increase of the sintered pellet density with the enhancement of the lithium concentration at the grain boundaries.

Ionic conductivity of the lithium titanium phosphate (Li/sub 1+x/M/sub x/Ti/sub 2-x/(PO/sub 4/)/sub 3/, M=Al, Sc, Y, and La) systems

High lithium ionic conductivity was obtained in Li/sub 1+X/M/sub X/Ti/sub 2-X/(PO/sub 4/)/sub 3/ (M=Al, Sc, Y, and La) systems. Lithium titanium phosphate, LiTi/sub 2/(PO/sub 4/)/sub 3/, is composed of both TiO/sub 6/ octahedra and PO/sub 4/ tetrahedra, which are linked by corners to form a three dimensional network, with a space group R3-barC. Some workers have already described that the conductivity increased considerably if Ti/sup 4+/ in LiTi/sub 2/(PO/sub 4/)/sub 3/ was substituted by slightly larger cations such as Ga/sup 3+/(1),Sc/sup 3+/(2), and In/sup 3+/(3,4). These results are similar to each other because of their close ionic radii. In this communication, substitution effects of Ti/sup 4+/ in LiTi/sub 2/(PO/sub 4/)/sub 3/ by various ions (Al/sup 3+/, Sc/sup 3+/, Y/sup 3+/, and La/sup 3+/) on their conductivities are reported.

Electrical property and sinterability of LiTi2(PO4)3 mixed with lithium salt (Li3PO4 or Li3BO3)

Abstract A lithium salt (Li 3 PO 4 or Li 3 BO 3 ) was added to LiTi 2 (PO 4 ) 3 to obtain a dense pellet of the phosphate. The porosity of the sintered pellets decreased and the conductivity was enhanced by the utilization of a binder. A maximum conductivity of 3.0 × 10 −4 S·cm −1 at 298 K was obtained for a sample of LiTi 2 (PO 4 ) 3 −0.2Li 3 BO 3 . The activation energy for the lithium migration at grain boundaries was decreased by the addition of lithium salt. The reason for the conductivity enhancement was attributed to a decrease in the activation energy for the lithium migration at the grain boundary and an increase in the contact area between grains. The conductivity of the bulk component was also increased by the enhancement of Li + -ion migration at grain boundaries.

Ionic conductivity and sinterability of lithium titanium phosphate system

Abstract Lithium titanium phosphates mixed with various metal ions of M 3+ (M=Al, Cr, Ga, Fe, Sc, In, Lu, Y, or La), Li 1+ x M x Ti 2− x (PO 4 ) 3 systems, were prepared, and their properties were investigated. The conductiv ity was enhanced and the porosity of the sintered pellets decreased by the partial replacement of Ti 4+ with the M 3+ ion. The porosity was considerably influenced by the ionic radius of the M 3+ ion. The sinterability was greatly related to the increase of lithium concentrations at the grain boundary. The conductivity enhancement by the substitution mainly resulted from the densification of the sintered pellets.

The Electrical Properties of Ceramic Electrolytes for LiM x Ti2 − x ( PO 4 ) 3 + yLi2 O , M = Ge , Sn , Hf , and Zr Systems

The electrical properties of systems of , were examined in detail. The conductivity and the sinterability increased with the amount of excess lithium oxide in the phosphate. The secondary phase acts as a flux to accelerate the sintering process and to obtain high conductivity grain boundaries. The conductivity decreased and the activation energy of the bulk component for Li+ migration increased by the partial substitution of Tr4+for M4+ in systems of . A minimum activation energy of 0.28–0.30 eV, was obtained for the sample with ca. 1310 A3 in the cell volume. has the most suitable tunnel size for a Li+ migration through the NASICON‐type network structure.

Electrical properties and crystal structure of solid electrolyte based on lithium hafnium phosphate LiHf2(PO4)3

Abstract The electrical properties and the crystal structure were investigated for the ceramic electrolytes based on LiHf 2 (PO 4 ) 3 . The conductivity enhanced by the Li 2 O addition with LiHf 2 (PO 4 ) 3 system and by the increase of x for Li 1+ x M x Hf 2− x (PO 4 ) 3 (M=Cr, Fe, Sc, In, Lu or Y) systems. The P2 1 /n monoclinic phase transformed to NASICON-type R 3 c rhombohedral phase at above 1173 K. The activation energy for Li + ion migration was decreased by the phase transition. The activation energy for bulk component was 0.42 eV for the NASICON-type structure. A maximum conductivity at 298 K is 1.7 × 10 −4 S·cm −1 for the sample of Li 1.2 Fe 0.2 Hf 1.8 (PO 4 ) 3 .

Potentiometric chlorine gas sensor using BaCl2-KCl solid electrolyte: The influences of barium oxide contamination

Abstract The effects of BaO contamination on the behaviour of a Cl 2 gas sensor using a 0.97BaCl 2 -0.03KCl solid electrolyte have been investigated. The addition of BaO to the electrolyte is found to produce unfavourable effects on both the measuring and reference electrodes through a side reaction such as BaO + Cl 2 → BaCl 2 + (1/2)O 2 . The presence of BaO in the vicinity of the measuring electrode results in decreases in the e.m.f. and rate of response, especially when the Cl 2 gas concentration is lowered to a few tens of ppm. Its presence near to the reference electrode, on the other hand, results in the upward deviation of the e.m.f. over the entire range of Cl 2 concentration. The probe prepared in vacuo, free of such BaO contamination, gives e.m.f. values in good agreement with the theoretical ones for Cl 2 gas concentrations between 10 and 1000 ppm. In contrast, the probe prepared in air shows a slower response as well as a more extensive deviation from theory in the low Cl 2 concentration range, suggesting that the electrolyte near the measuring electrode is contaminated with BaO.

Application of SO2 Sensor Using .BETA."-Alumina Solid Electrolyte to Practical Process in Copper Smelting Plant.

The present study was undertaken to investigate the practical use of SO2 gas sensor employing β″-alumina solid electrolyte in the field of industry. In the cell with β″-alumina solid electrolyte, the use of (β″+β″)-alumina coexistent mixture in air as a solid reference electrode lead to a simple structure of the SO2 gas sensor. In this paper we reported the practical application of SO2 gas sensor with the following cell in copper smelting plants.Pt, (β+β″)-alumina in air/β″-alumina/S02+O2+SO3, PtFrom the present experiments the following conclusions were obtained.1) The present experimental cell showed a satisfactory response and the data agreed very closely with those obtained by another analytical method (non-dispersive infrared rays).2) In a long period of measuring, the emfs of this sensor varied with the lapse of time. However it was confirmed that its reproducibility is obtained by the correction of the calibration curve once a few days.