First-Principles Studies on Cation Dopants and Electrolyte|Cathode Interphases for Lithium Garnets

Lithium garnet with the formula Li7La3Zr2O12 (LLZO) has many properties of an ideal electrolyte in all-solid state lithium batteries. However, internal resistance in batteries utilizing these electrolytes remains high. For widespread adoption, the LLZO’s internal resistance must be lowered by increasing its bulk conductivity, reducing grain boundary resistance, and/or pairing it with an appropriate cathode to minimize interfacial resistance. Cation doping has been shown to be crucial in LLZO to stabilize the higher conductivity cubic structure, yet there is still little understanding about which cations have high solubility in LLZO. In this work, we apply density functional theory (DFT) to calculate the defect energies and site preference of all possible dopants in these materials. Our findings suggest several novel dopants such as Zn2+ and Mg2+ predicted to be stable on the Li- and Zr-sites, respectively. To understand the source of interfacial resistance between the electrolyte and the cathode, we inves...