Effect of acid treatment of Li₇La₃Zr₂O₁₂ on ionic conductivity of composite solid electrolytes

Abstract

The garnet-type metal oxide Li7La3Zr2O12(LLZO) is considered to be one of the most promising compounds for solid lithium ion batteries because of its high ionic conductivity at room temperature and excellent chemical stability with the metal Li. LLZO is unstable in humid air and easily forms Li2CO3 on the surface, which leads to the decrease of ion conductivity. In this paper, chemical treatment by oxalic acid is carried out to remove the lithium carbonate on the surface of LLZO. The results show that oxalic acid with a concentration ratio of 5% can completely remove lithium carbonate. Composite polymer electrolyte membranes fabricated by the polyvinylidene fluoride (PVDF)and LLZO before and after the acid treatment are prepared to evaluate the effect on ionic conductivity. The ionic conductivity is 1.4×10−4 Scm−1 and 9.0×10−4 S cm−1 for samples added the LLZO before and after the acid treatment, respectively.

Quasi-In Situ XPS Insights into the Surface Chemistry of Garnet-Type Li6.4La3Zr1.4Ta0.6O12 Solid-State Electrolytes: The Overlooked Impact of Pretreatments and a Direct Observation of the Formation of LiOH

“…Up to now, various pretreatments such as mechanical polishing, acid treatment, and heat treatment have been proposed to remove the passivation layer and expose the pristine surface of the solid electrolytes. − The exposed LLZTO surface by such pretreatments is used as the foundation of mechanistic studies on the surface chemistry and interfacial behavior of LLZTO. However, the potential concomitant contamination or damage to LLZTO caused by these pretreatments may have been overlooked.…”

Review on Impurity and Conductivity Issues of Garnet Type Li7La3Zr2O12: Mechanisms, Solutions, and Perspectives

“…Whereas the use of acrylic acid destroys the ceramic structures. Along with the removal of impurity peaks oxalic acid treatment also improves conductivity from 1.4 × 10 –4 S cm –1 (untreated) to 9.0 × 10 –4 S cm –1 (Oxalic acid treated) . Xueliang Sun et al have shown the successful removal of Li 2 CO 3 on the surface of LLZO by the rapid chemical method.…”

“…It can enhance ionic conductivity, improve stability, and reduce the interfacial resistance and contact angle between electrolyte and electrode. In LLZO, different dopants like Mg, Al, Si, Ca, Ti, Cr, Fe, Ga, Rb, Sr, Y, Nb, Mo, In, Sb, Te, Ba, Ce, Gd, Ta, and W − have been used. These dopants and their respective sites have been chosen considering their ionic radii and coordination number to improve the phase stability.…”