Abstract
All-Solid-State Lithium Batteries (ASSLBs) are promising since they may enable the use of high potential materials as positive electrode and lithium metal as negative electrode. This is only possible through solid electrolytes (SEs) stated large electrochemical stability window (ESW). Nevertheless, reported values for these ESWs are very divergent in the literature. Establishing a robust procedure to accurately determine SEs’ ESWs has therefore become crucial. Our work focuses on bringing together theoretical results and an original experimental set up to assess the electrochemical stability window of the two NASICON-type SEs Li1.3Al0.3Ti1.7(PO4)3 (LATP) and Li1.5Al0.5Ge1.5(PO4)3 (LAGP). Using first principles, we computed thermodynamic ESWs for LATP and LAGP and their decomposition products upon redox potentials. The experimental set-up consists of a sintered stack of a thin SE layer and a SE-Au composite electrode to allow a large contact surface between SE and conductive gold particles, which maximizes the redox currents. Using Potentiostatic Intermittent Titration Technique (PITT) measurements, we were able to accurately determine the ESW of LATP and LAGP solid electrolytes. They are found to be [2.65–4.6 V] and [1.85–4.9 V] for LATP and LAGP respectively. Finally, we attempted to characterize the decomposition products of both materials upon oxidation. The use of an O2 sensor coupled to the electrochemical setup enabled us to observe operando the production of O2 upon LAGP and LATP oxidations, in agreement with first-principles calculations. Transmission Electron Microscopy (TEM) allowed to observe the presence of an amorphous phase at the interface between the gold particles and LAGP after oxidation. Electrochemical Impedance Spectroscopy (EIS) measurements confirmed that the resulting phase increased the total resistance of LAGP. This work aims at providing a method for an accurate determination of ESWs, considered a key parameter to a successful material selection for ASSLBs.
Highlights
Since their commercialization in 1990, rechargeable lithium-ion batteries (LIBs) have revolutionized global communication and enabled the democratization of portable electronics
Computed results are coherent with one another, it proves that Grand Potential Phase Diagram (GPPD) is a robust and appropriate method to use to compute electrochemical stability window (ESW)
AlPO4 is found in our work and for Zhu et al Our computations predict the production of Li2Ti2(PO4)3, indicating a possible insertion of lithium in LATP at low potential
Summary
Since their commercialization in 1990, rechargeable lithium-ion batteries (LIBs) have revolutionized global communication and enabled the democratization of portable electronics. The limited electrochemical stability window (ESW) of organic liquid electrolytes (up to 4.2 Vvs. Li+/Li) limits the choice of positive electrode materials in LIBs. High potential positive electrode materials, such as LiNi0.5Mn1.5O4, LiNi0.8Co0.15Al0.05O2 and LiNixMnyCozO2 (Thackeray et al, 1983; Li, 1997; Liu et al, 1999; Yoshio et al, 2000), require the use of an electrolyte stable in the range of their operation potentials. High potential positive electrode materials, such as LiNi0.5Mn1.5O4, LiNi0.8Co0.15Al0.05O2 and LiNixMnyCozO2 (Thackeray et al, 1983; Li, 1997; Liu et al, 1999; Yoshio et al, 2000), require the use of an electrolyte stable in the range of their operation potentials To tackle these problems, researchers have been working toward developing a new generation of high-power lithium batteries, namely all-solid-state lithium batteries (ASSLBs)
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