Li_4–xGe_1–xP_xO₄, a Potential Solid-State Electrolyte for All-Oxide Microbatteries

Abstract

Solid-state electrolytes for Li-ion batteries are attracting growing interest as they allow building safer batteries, also using lithium metal anodes. Here we studied a compound in the lithium superionic conductor (LISICON) family, i.e. Li4-xGe1-xPxO4 (LGPO). Thin films were deposited via pulsed laser deposition and their electrical properties were compared with ceramic pellets. A detailed characterization of the microstructure shows that thin films can be deposited fully crystalline at higher temperatures but also partially amorphous at room temperature. The conductivity is not strongly influenced by the presence of grain boundaries, exposure to air or lithium deficiencies. First-principles molecular dynamics simulations were employed to calculate the lithium ion diffusion profile and the conductivity at various temperatures of the ideal LGPO crystal. Simulations gives the upper limit of conductivity for a defect free crystal, which is in the range of 10-2 S cm-1 at 300 °C The ease of thin film fabrication, the room-temperature Li-ion conductivity in the range of a few µS cm-1 make LGPO very appealing electrolyte material for thin film all-solid-state all-oxide microbatteries.

Recent advancements in solid electrolytes integrated into all-solid-state 2D and 3D lithium-ion microbatteries

“…174,178,179 So far, Gilardi et al deposited a thin-lm LISICON-type Li 4Àx Ge 1Àx P x O 4 (LGPO) by PLD and characterized it. 180 It was observed that although LGPO fabricated at room temperature had higher porosity, roughness and some contamination on the surface, the ionic conductivity was not much affected by the low-temperature deposition and was in the order of 10 À6 S cm À1 . 180 Therefore, the ease of fabrication, wide electrochemical window, and relatively reasonable conductivity make LGPO a potentially interesting electrolyte for solid-state thin-lm batteries, and thus, further testing of this electrolyte in microbattery required.…”

“…180 It was observed that although LGPO fabricated at room temperature had higher porosity, roughness and some contamination on the surface, the ionic conductivity was not much affected by the low-temperature deposition and was in the order of 10 À6 S cm À1 . 180 Therefore, the ease of fabrication, wide electrochemical window, and relatively reasonable conductivity make LGPO a potentially interesting electrolyte for solid-state thin-lm batteries, and thus, further testing of this electrolyte in microbattery required. In general, more testing of the microbattery with LISICON-based electrolytes is expected once the appropriate chemical composition of the electrolytes is found that will satisfy the conductivity and stability criteria.…”

High performance LATP thin film electrolytes for all-solid-state microbattery applications

“…50 In the LISICON family, recent reports have also suggested the presence of nanocrystals in an amorphous matrix under certain conditions. 51 Amorphization has also been studied in this family as a strategy to improve ionic conductivity. 52 The ionic conductivity of the fabricated LATP thin lms was evaluated at different temperatures by means of EIS.…”

Pulsed Laser Deposition as a Tool for the Development of All Solid‐State Microbatteries

“…Recently, deposition of Li 4− x Ge 1− x P x O 4 (LGPO) thin films at room temperature and 500 °C was reported [158] …”