Lithium zirconate (LZO) is an attractive material for many applications. For example, it has been extensively studied as a solid absorbent for reversible CO₂ capture at elevated temperatures, as a ceramic breeder for nuclear reactors, and as a coating for high-capacity cathode materials in lithium ion batteries (LIBs).

The Li⁺ transport is critical to the functionality of LZO in these applications. For CO₂ adsorption, Li⁺ diffusion is a critical factor affecting both surface absorption and high-temperature CO₂ desorption processes. For LIBs, LZO can provide fast migration pathways for Li⁺ at the electrolyte-electrode interface when it is used as a coating for electrodes. For nuclear fusion, the Li⁺ migration through vacant sites inside LZO grains is closely related to its performance in tritium (3H) release. Therefore, understanding the Li⁺ migration mechanism and, more importantly, enhancing Li⁺ transport in LZO is important to many applications.

Control of dopant concentration is an effective way to tune the Li⁺ conductivity. However, the electrical conductivity of doped LZO and the relationship between defect chemistry and electrical conductivity in doped LZO have not been reported. In addition, the effect of oxygen concentration on Li⁺ diffusion has not been fully understood. Here, we study the defect chemistry and electrical properties of the undoped LZO and a series of cation-doped LZO samples. We establish a relationship between Li⁺ conductivities and doping-induced oxygen/Li nonstoichiometries. We demonstrate that the conductivity results can be understood by unveiling the critical role of oxygen vacancies in Li⁺ transport. An improved CO₂ absorption performance of doped LZO materials will also be discussed.