Optimization of sintering process on Li1+Al Ti2-(PO4)3 solid electrolytes for all-solid-state lithium-ion batteries

Abstract

In this study, a NASICON-structured Li1.3Al0.3Ti1.7(PO4)3 (LATP) powder is prepared by hydrothermal methods followed by calcination, cold pressing and post-sintering processes. The white, solid product is characterized thoroughly using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS). The conductivity of the material is measured by a impedance spectroscopy as a function of temperature. Initially, hydrothermal synthesis yields a material isostructural with the orthorhombic oxyphosphate, LiTiOPO4. EDS analysis shows that the distribution of aluminum throughout this material is uniform. A systematic study is then performed to investigate how altering the sintering parameters (such as powder pre-sintering temperature and pellet sintering temperature) affect the formation of LATP. The structure is determined by Rietveld refinement against XRD data and the effects of sintering temperature on porosity, microstructure and electrical conductivity were resolved. The experimental results show that the optimum pre-sintering and sintering temperatures of LATP powders and pellets respectively are 900 ℃ and 1100 ℃. These conditions produce materials with the highest density (99.07% of theoretical), superior conductivity (grain-, grain boundary-and total lithium-ion conductivities of 6.5710 -4 , 4.5910 -4 and 2.7010 -4 S cm -1 , respectively) and with an activation energy for Li motion of 0.17 eV.

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

“…Furthermore, Siyal et al [385] analyzed a gel polymer electrolyte with 15 wt.% LATP composite, and few other researchers studied bare and LATP composite electrodes [379,[386][387][388]. Yen et al [389] characterized LATP powders prepared by hydrothermal synthesis followed by calcination (900-1100 • C), cold pressing (90 MPa), and post sintering, which exhibit ionic conductivity of grain and grain boundary of 6.57 × 10 −4 and 4.59 × 10 −4 S cm −1 , respectively. The fabricated NCM523|LATP|artificial graphite pouch cell delivered a high reversible capacity of 16.7 mAh at 0.5C after 360 cycles with 63.2% capacity retention (voltage range, 2.80-4.25 V).…”

Preparation of Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte via a sol-gel method using various Ti sources

“…Table 3 shows a comparison of ionic conductivity of LATP sintered at various conditions. In our sol-gel method, high conductive LATP was obtained comparing with other studies at similar sintering conditions [35][36][37][38]. Some studies used sintering additive such as LiF, LiBO 2 and so on.…”

Stabilizing the NASICON Solid Electrolyte in an Inert Atmosphere as a Function of Physical Properties and Sintering Conditions for Solid-State Battery Fabrication

“…The secondary phase Ti 2 O 3 (Ti 3+ ) can be expected only if reduction of Ti (Ti 4+ → Ti 3+ ) occurs in an argon atmosphere; this is also the reason for the color change of pellets . However, some of the secondary phases are reported beneficial for the sintering process such as AlPO 4 which helps in removing voids/pores and increases the density of LATP. , Similarly, optimum content of LiTiOPO 4 helps in decreasing the sintering temperature and enhances the densification . However, the excess content of these phases hinders Li-ion diffusion at the grain boundary due to the low conductivity of these phases. ,, The phase quantification of LATP using Rietveld refinement could not be achieved successfully due to multiphase compositions of samples and common peak positions of multiple phases.…”

“…The ionic conductivity of LATP has been reported to be up to 10 –4 to 10 –3 S cm –1 at room temperature . The conductivity of LATP depends on many factors such as the doping level of Al, − density of sintered LATP, ,− sintering temperature, ,, secondary phases present in the sample, − , microstructure of sintered LATP, ,,− synthesis method, ,,, etc. However, in the above-mentioned studies on LATP solid electrolytes, sintering was performed in an air or oxygen environment. ,− …”