Effect of Sm3+ Substitutions on the Lithium Ionic Conduction and Relaxation Dynamics of Li5+2xLa3Nb2−xSmxO12 Ceramics

M S Ahmad ,Adil Alshoaibi,Hassan A Khater,Abdullah Aljaafari,Mohamed Helmi Hadj Alouane ,H Mahfoz-Kotb

doi:10.3390/cryst11020095

M S Ahmad , Adil Alshoaibi + Show 4 more

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https://doi.org/10.3390/cryst11020095

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Abstract

In the present work, we studied the effects of substitutional Sm3+ ions on the ionic conduction properties of Li5+2xLa3Nb2−xSmxO12 (LLN-Sm) ceramics with x = 0.0—0.6. The investigated final ceramics, prepared by solid state reaction, were sintered at 1000 °C for 12 h. XRD investigations showed the formation of the cubic garnet phase for all of the studied samples. The ionic conductivity was found to increase with Sm3+ content, with the highest value of 7.04 × 10−5 S/cm for the Li5+2xLa3Nb2−xSmxO12 sample compared to 7.49 × 10−6 S/cm for the pure LLN sample, both at RT. Lithium ion mobilities of LLN-Sm garnets at different temperatures were estimated. Considerable enhancement of mobility, the main factor leading to ionic conductivity improvement, was obtained for samples with Sm3+ substitutions. Relaxation processes were studied by the electric modulus, and the corresponding activation energy was found to be very similar to the ionic conduction process.

Highlights

Rechargeable lithium ion batteries are major energy reservoirs/depots in our daily life, where they are used in various electronic devices
Nyquist impedance plots of the Li5 La3 Nb2 O12 (LLN)-Sm25 ceramics are shown in Figure 2 at selected temperatures as a representative example
Sm3+ -substituted Li5+2x La3 Nb2−x Smx O12 (LLN-Sm) ceramics with x = 0–0.6 compositions were successfully synthesized by solid-state reaction and conventional sintering techniques

Summary

Introduction

Rechargeable lithium ion batteries are major energy reservoirs/depots in our daily life, where they are used in various electronic devices. The current batteries suffer safety and capacity loss issues due to the used liquid electrolytes [1,2,3]. These drawbacks could be eliminated by using solid lithium electrolytes as an alternative. The necessary range of the ionic conductivity for practical applications, 10−3 —10−2 S/cm, is difficult to achieve in most solid lithium ionic conductors. This is one of the most challenging hurdles in the development of all solid-state batteries [1,2,3]. Different inorganic crystalline and glassy lithium ion conducting materials, such as Li7 P3 S11 [4], Li10 GeP2 S12 [5], Li2 S-B2 S3 [6], Li1+x Alx Ge2−x (PO4 )3 [7], Li1+x Alx Ti2−x (PO4 )3 [8,9] and

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