Thermophysical Properties of Lithium Aluminum Germanium Phosphate with Different Compositions

Abstract

The NASICON system LAGP (Li 1+x Al x Ge 2−x (PO 4 ) 3 was studied, which is a candidate material for solid state electrolytes. LAGP substrates with different compositions (x = 0.3-0.7) were prepared using a melt quenching route with subsequent heat treatment. In order to develop a better understanding of the relationships between the structure and the ionic as well as the thermal conductivity, respectively, the samples were characterized by X-ray diffraction. The ionic conductivity was measured using impedance spectroscopy while the thermal diffusivity and the specific heat were determined by Laser Flash technique and differential scanning calorimetry, respectively. Additionally, thermal analysis was performed in order to evaluate the thermal stability a higher temperatures and, also to identify the optimum temperature range of the thermal post-processing. The measured values of the ionic conductivities were in the range of 10 −4 Ω −1 ·cm −1 to 10 −3 Ω −1 ·cm −1 at room temperature, but exhibited an increasing behavior as a function of temperature reaching a level of the order 10 −2 Ω −1 · cm −1 above 200 °C. The thermal conductivity varies only slowly as a function of temperature but its level depends on the composition. The apparent specific heat depends also on the composition and exhibits enthalpy changes due to phase transitions at higher temperatures for LAGP samples with x > 0.5. The compositional dependencies of the ionic and thermal transport properties are not simply correlated. However, the compound with the highest Li-doping level shows the highest ionic conductivity but the lowest thermal conductivity, while the lowest doping level is associated with highest thermal conductivity but the lowest ionic conductivity.LAGP glasses were prepared using the melt-quench-route, which has been successfully proved in former studies [6,10]. Li 2 CO 3 (Fluka, 99.0 %), Al 2 O 3 (Sigma-Aldrich, 98.5 %), P 2 O 5 (Analar Normapur, 99.1 %) and GeO 2 (Alfa Aesar,

Ionic and Thermal Transport in Na-Ion-Conducting Ceramic Electrolytes

“…Studies of the specific heat capacity in Li-conducting NASICON systems, namely, LAGP Li 1+x Al x Ge 2−x (PO 4 ) 3 [41] with different compositions showed similar high-temperature behavior. However, the LAGP exhibited the anharmonic contributions for all studied compositions.…”

Sulfide and Oxide Inorganic Solid Electrolytes for All-Solid-State Li Batteries: A Review

“…An SSB was fabricated using LAGP-30 wt.% PPC-SCE, LiFePO4, and Li metal as the composite electrolyte, cathode, and anode, respectively. The battery was formatted at 80 °C for 12 h to ensure optimal contact between the electrodes and electrolyte, and then it was subjected to galvanostatic Bock et al [342] reported that the thermal conductivity of LAGP was approximately 0.5 ± 0.2 W K −1 m −1 ; moreover, Rohde et al [398] reported other thermo-physical properties of the (Li 1+x Al x Ge 2−x )(PO 4 ) 3 solid electrolyte with x = 0.3-0.7. Recently, Paolella et al [438] reported the optimum conditions for densification of Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 at a low temperature of 650 • C using hot-press technique (56 MPa applied pressure); this solid electrolyte was used in all-solid-state battery with LiFePO 4 cathode without addition of any further polymer or liquid electrolyte additives.…”

“…Sodium zirconium phosphate (NaZr 2 (PO 4 ) 3 (NZP) is the parent compound of the Na-based super ionic conductor named NASICON [ 359 , 360 , 361 , 362 , 363 , 364 , 365 , 366 , 367 , 368 , 369 , 370 , 371 , 372 , 373 , 374 , 375 , 376 , 377 , 378 , 379 , 380 , 381 , 382 , 383 , 384 , 385 , 386 , 387 , 388 , 389 , 390 , 391 , 392 , 393 , 394 , 395 , 396 , 397 , 398 , 399 , 400 , 401 , 402 , 403 , 404 , 405 , 406 ,…”

“…For example, the use of phosphorous source (H 3 PO 4 ) as precursor provides the best LAGP phase purity and the highest ionic conductivity of ~5 × 10 −4 S cm −1 at 25 °C. In addition, few studies on the synthesis, conductivity (~4 × 10 −4 S cm −1 , see Table 3 [ 365 ]) and interface mechanisms, and physical and electrochemical properties of LAGP have been published since 2019 [ 49 , 342 , 394 , 395 , 396 , 397 , 398 , 399 , 400 , 401 , 402 , 403 , 404 , 405 , 406 , 407 , 408 , 409 , 410 , 411 , 412 , 413 , 414 , 415 , 416 , 417 , 418 , 419 , 420 , 421 , 422 , 423 , 424 , 425 , 426 , 427 , 428 , 429 , 430 , 431 , 432 , 433 , 434 ...…”

“…Bock et al [ 342 ] reported that the thermal conductivity of LAGP was approximately 0.5 ± 0.2 W K −1 m −1 ; moreover, Rohde et al [ 398 ] reported other thermo-physical properties of the (Li 1+ x Al x Ge 2− x )(PO 4 ) 3 solid electrolyte with x = 0.3–0.7. Recently, Paolella et al [ 438 ] reported the optimum conditions for densification of Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 at a low temperature of 650°C using hot-press technique (56 MPa applied pressure); this solid electrolyte was used in all-solid-state battery with LiFePO 4 cathode without addition of any further polymer or liquid electrolyte additives.…”