Abstract
Garnet solid state electrolytes have been considered as potential candidates to enable next generation all solid state batteries (ASSBs). To facilitate the practical application of ASSBs, a high room temperature ionic conductivity and a low interfacial resistance between solid state electrolyte and electrodes are essential. In this work, we report a study of cerium doped Li5La3Nb2O12 through X-ray pair distribution function analysis, impedance spectroscopy and electrochemical testing. The successful cerium incorporation was confirmed by both X-ray diffraction refinement and X-ray pair distribution function analysis, showing the formation of an extensive solid solution. The local bond distances for Ce and Nb on the octahedral site were determined using X-ray pair distribution function analysis, illustrating the longer bond distances around Ce. This Ce doping strategy was shown to give a significant enhancement in conductivity (1.4 × 10-4 S cm-1 for Li5.75La3Nb1.25Ce0.75O12, which represents one of the highest conductivities for a garnet with less than 6 Li) as well as a dramatically decreased interfacial resistance (488 Ω cm2 for Li5.75La3Nb1.25Ce0.75O12). In order to demonstrate the potential of this doped system for use in ASSBs, the long term cycling of a Li//garnet//Li symmetric cell over 380 h has been demonstrated.
Highlights
State-of-the-art lithium ion batteries (LIBs) have dominated the energy storage market for more than 2 decades because of their long cycle life and high energy and power densities over other battery systems.[1,2,3] Nowadays, the increasing demand in developing electrical vehicles (EVs) needs higher energy density, but more importantly, requires improved safety properties.[4]
Garnet lithium ion conductors have attracted increasing interest in the last decade due to their relatively good electrochemical stability against Li metal/cathode materials, and high room temperature lithium ionic conductivity compared to other solid state electrolyte materials.[6,7,8]
Li2La2CeO6 and CeO2 impurity phases were detected for compositions with x = 1, which is consistent with the leveling off of the cell parameter increase; from these data, a solid solution limitation around x = 0.85 is estimated
Summary
State-of-the-art lithium ion batteries (LIBs) have dominated the energy storage market for more than 2 decades because of their long cycle life and high energy and power densities over other battery systems.[1,2,3] Nowadays, the increasing demand in developing electrical vehicles (EVs) needs higher energy density, but more importantly, requires improved safety properties.[4].
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