Nonstoichiometry and Li‐ion transport in lithium zirconate: The role of oxygen vacancies

Abstract

Understanding Li‐ion migration mechanisms and enhancing Li‐ion transport in Li2ZrO3 (LZO) is important to its role as solid absorbent for reversible CO2 capture at elevated temperatures, as ceramic breeder in nuclear reactors, and as electrode coating in high‐voltage lithium‐ion batteries (LIBs). Although defect engineering is an effective way to tune the properties of ceramics, the defect structure of LZO is largely unknown. This study reports the defect structure and electrical properties of undoped LZO and a series of cation‐doped LZOs: (i) depending on their charge states, cation dopants can control the oxygen vacancy concentration in doped LZOs; (ii) the doped LZOs with higher oxygen vacancy concentrations exhibit better Li+ conductivity, and consequently faster high‐temperature CO2 absorption. In fact, the Fe (II)‐doped LZO shows the highest Li‐ion conductivity reported for LZOs, reaching 3.3 mS/cm at ~300°C that is more than 1 order of magnitude higher than that of the undoped LZO.

CO2 capture using solid sorbents: Fundamental aspects, mechanistic insights and recent advances

“…The net effect of this is an improvement of the oxide ionic conductivity and improvement of the overall rate of CO2 absorption. This has been observed in practice for Fe-doped Li4SiO4 [584], Fe-doped Li2ZrO3 [585], [586], Fe-doped Li5AlO4 [583] and Fe-doped NaCoO2 [587].…”

“…There have been a number of studies that aimed at elucidating the effect of dopant on ionic conductivity. Zhan et al [586] studied the connection between aliovalent doping of Li2ZrO3 leading to the creation of oxygen vacancies, and the resulting change in Li ionic conductivity.…”

Gallium‐Doping Effects on Structure, Lithium‐Conduction, and Thermochemical Stability of Li7‐3xGaxLa3Zr2O12 Garnet‐Type Electrolytes

“…The use of Ga as Li‐site dopant has been reported to improve Li‐ion conductivity about an order of magnitude (2.6×10 −4 to 1.2×10 −3 S cm −1 ) greater than that of Al, as the ionic radius of Ga 3+ compared to that of Al 3+ is larger in four‐ and six‐coordination conditions thereby expanding the tetrahedral and octahedral gap [9] . Yet, the exchange of a relatively larger multivalent cation, such as Ga, into Li sites is thought to decrease the length of lithium migration pathway by contraction of the solid‐phase structure, thereby enhancing ion transport through the structure [10–12] . Thus, there may be a balance between dopant cation size and structural optimization of Li‐ion conduction.…”

Zirconium‐Based Materials for Electrochemical Energy Storage

“…Moreover, it is obvious that introducing dopants could be effective methods to create the oxygen deficiency for Li 2 ZrO 3 to facilitate Li + transport. Zhan et al . show that the doping Zr sites with Al, Ti, Fe, and Ga could improve Li‐ion conductivity of Li 2 ZrO 3 .…”