Abstract
Lithium argyrodite Li6PS5Cl powders are synthesized from Li2S, P2S5, and LiCl via wet milling and post-annealing at 500°C for 4 h. Organic solvents such as hexane, heptane, toluene, and xylene are used during the wet milling process. The phase evolution, powder morphology, and electrochemical properties of the wet-milled Li6PS5Cl powders and electrolytes are studied. Compared to dry milling, the processing time is significantly reduced via wet milling. The nature of the solvent does not affect the ionic conductivity significantly; however, the electronic conductivity changes noticeably. The study indicates that xylene and toluene can be used for the wet milling to synthesize Li6PS5Cl electrolyte powder with low electronic and comparable ionic conductivities. The all-solid-state cell with the xylene-processed Li6PS5Cl electrolyte exhibits the highest discharge capacity of 192.4 mAh·g−1 and a Coulombic efficiency of 81.3% for the first discharge cycle.
Highlights
Inorganic solid electrolytes-based all-solid-state lithium-ion batteries (ASSLIBs), are expected to replace liquid electrolytes-based conventional lithium-ion batteries (LIBs) owing to their advantages, such as safety, higher energy density, and wider operation temperature range (Gao et al, 2018; Lee et al, 2019; Yu et al, 2021)
For the as-milled powder mixture samples (Figure 1A), characteristic peaks of Li2S and LiCl crystalline phases were observed in all the samples, whereas no peaks corresponding to the P2S5 phase were observed
A single-phase Li6PS5Cl powder was synthesized from Li2S, P2S5, and LiCl powder mixture via wet ball milling with various organic solvents and post-annealing
Summary
Inorganic solid electrolytes-based all-solid-state lithium-ion batteries (ASSLIBs), are expected to replace liquid electrolytes-based conventional lithium-ion batteries (LIBs) owing to their advantages, such as safety, higher energy density, and wider operation temperature range (Gao et al, 2018; Lee et al, 2019; Yu et al, 2021). A cold-pressed sulfide electrolyte has higher ionic conductivity than an oxide electrolyte sintered at high temperatures (Yu et al, 2018; Huang et al, 2021). Sulfide-based solid electrolytes such as lithium argyrodite (Li6PS5Cl) are typically prepared by mechanical milling and subsequent annealing processes. The precursor materials (Li2S, P2S5, and LiCl) are dry-milled in a high-speed planetary ball mill, and the obtained powder mixture is annealed in a vacuum furnace or in an Ar-filled ampule to obtain a crystalline argyrodite phase. The lithium argyrodite electrolytes prepared via the aforementioned process exhibit a room temperature (25°C) ionic conductivity exceeding 10–3 S·cm−1 (Boulineau et al, 2012; Yu et al, 2016; Yu et al, 2017). The precursors adhere to the milling jar wall or grinding media (normally, zirconia balls) because of their sticky nature, which can cause compositional and
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