Influence of AlPO₄ Impurity on the Electrochemical Properties of NASICON‐Type Li_1.5Al_0.5Ti_1.5(PO₄)₃ Solid Electrolyte

Abstract

Densification of ceramic electrolytes is a key enabler in producing electrolyte pellets for solid-state batteries. This requires understanding the correlation between the starting grain size of electrolytes, chemical phase evolution and degree of compaction which determine ion conductivity and chemical stability of solid electrolytes. In our work we were able to optimize the densification process of LATP at 700 °C with a high total ionic conductivity of 3.45 × 10 À 4 S cm À 1 after hot pressing, balancing pristine LATP crystallite size and AlPO 4 impurity formation. By combining several techniques such as in situ heating X-ray diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR), we explored the formation mechanism of AlPO 4 during the synthesis process of NASICON-type Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 (LATP) electrolyte and we showed the effects of the annealing temperature on the crystal size of the material. Density functional theory (DFT) calculations on the chemical stability of the electrolyte imply a metastable behaviour of LATP furtherly enhanced by particle nanostructuring at high temperature. Our results point to facile manufacturing of ceramic electrolytes towards energy dense and safe solid-state battery technology.

Optimizing Li1.3Al0.3Ti1.7(PO4)3 Particle Sizes toward High Ionic Conductivity

“…The observed and calculated XRD patterns showed fairly good agreement with good reliability factors ( R wp = 9.36%). There was an AlPO 4 phase in the samples, which might originate from the decomposition 18Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 ↔ 17Li 1.2 Al 0.2 Ti 1.8 (PO 4 ) 3 + 2AlPO 4 + Li 3 PO 4 or from the intermediate reaction Al 2 O 3 + 2NH 4 H 2 PO 4 → 2AlPO 4 + 2NH 3 ↑ + 3H 2 O↑. , AlPO 4 cannot conduct Li + , which is harmful for obtaining highly conducive LATP ceramic electrolyte. ,− The phase contents are given in Figure b. The highest occupation amount of AlPO 4 phase is 2.28% in the medium-sized sample, which acted as a binder between grains to facilitate the densification of ceramics. , The contents were 1.71% and 1.24% in coarse and fine samples.…”

Oxide‐based ternary composite solid‐state electrolyte for next‐generation lithium batteries

“…21 The achievement of superior outcomes and elevated ionic conductivity is facilitated by the appropriate combination of densification level, AlPO 4 phase, and voids. 22 Wei Xiong et al created a solid composite electrolyte by blending PVDF-HFP, Li 1.3 Al 0.3-Ti 1.7 (PO 4 ) 3 (LATP), and inorganic fillers of flower-like CeO 2 particles enriched with oxygen vacancies. The resulting composite SSEs have a wide electrochemical window of 5.1 V and high ionic conductivity at RT, making them suitable for use in various electrochemical devices.…”

“…The facilitation of Li + ion migration by these voids contributes to the material's ionic conductivity 21 . The achievement of superior outcomes and elevated ionic conductivity is facilitated by the appropriate combination of densification level, AlPO 4 phase, and voids 22 . Wei Xiong et al created a solid composite electrolyte by blending PVDF‐HFP, Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP), and inorganic fillers of flower‐like CeO 2 particles enriched with oxygen vacancies.…”