Electrochemical Characterization of a Drawn Thin-Film Glassy Oxide Electrolyte Material for Solid-State Battery Applications

Abstract

Solid-state batteries present many advantages over liquid electrolyte systems, enabling the use of lithium metal anodes due to the non-flammable nature of the inorganic electrolyte. Glassy materials in particular are promising candidates as solid electrolytes due to their highly tunable properties, the absence of grain boundaries, and their ease of processability. The large compositional window of glassy materials allows for optimizing glass-forming ability and conductivity, while the lack of grain boundaries may be beneficial in preventing lithium dendrite formation. While lithium metaphosphate (LiPO3) has a low room temperature ionic conductivity (σ25°C = 1.6 ∙ 10-9 S/cm) that limits its use in solid-state batteries, oxides present similar processability and higher chemical and electrochemical stability than their higher conductivity sulfide analogues. LiPO3 was chosen for a preliminary investigation into the effects and challenges of decreasing electrolyte thickness due to its low processing temperature and ease of fabrication. The electrochemical behavior of drawn thin-film LiPO3 was studied through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic symmetric cell cycling. These results show that with higher conducting oxy-sulfide glassy electrolyte materials, drawn thin-film electrolytes are a viable and valuable research direction.