Abstract
Solid-state lithium batteries are generally considered as the next-generation battery technology that benefits from inherent nonflammable solid electrolytes and safe harnessing of high-capacity lithium metal. Among various solid-electrolyte candidates, cubic garnet-type Li7La3Zr2O12 ceramics hold superiority due to their high ionic conductivity (10–3 to 10–4 S cm−1) and good chemical stability against lithium metal. However, practical deployment of solid-state batteries based on such garnet-type materials has been constrained by poor interfacing between lithium and garnet that displays high impedance and uneven current distribution. Herein, we propose a facile and effective strategy to significantly reduce this interfacial mismatch by modifying the surface of such garnet-type solid electrolyte with a thin layer of silicon nitride (Si3N4). This interfacial layer ensures an intimate contact with lithium due to its lithiophilic nature and formation of an intermediate lithium–metal alloy. The interfacial resistance experiences an exponential drop from 1197 to 84.5 Ω cm2. Lithium symmetrical cells with Si3N4-modified garnet exhibited low overpotential and long-term stable plating/stripping cycles at room temperature compared to bare garnet. Furthermore, a hybrid solid-state battery with Si3N4-modified garnet sandwiched between lithium metal anode and LiFePO4 cathode was demonstrated to operate with high cycling efficiency, excellent rate capability, and good electrochemical stability. This work represents a significant advancement toward use of garnet solid electrolytes in lithium metal batteries for the next-generation energy storage devices.
Highlights
The ceiling of energy density allowed by commercial intercalation chemistries approaches 300 Wh/kg, while any attempt to push the energy density higher must face the risks imposed by highly flammable organic electrolyte solvents
The poor interfacing between Li0 and garnet-type Al-LLZO solid-state electrolyte by introducing a sputter-coated thin Si3N4 intermediate layer was addressed
Si3N4@Al-LLZO solid electrolyte paired with Li0 as anode and LFP as cathode exhibited stable cycling performance with excellent Coulombic efficiency compared to that for bare garnet
Summary
Lithium-ion batteries (LIBs) are used worldwide as the workhorse for powering applications.[1,2] The ceiling of energy density allowed by commercial intercalation chemistries approaches 300 Wh/kg, while any attempt to push the energy density higher must face the risks imposed by highly flammable organic electrolyte solvents. Liquid electrolytes impose limitations on performance of high-voltage cathodes, due to their lower anodic stability.[4] development of high-energy and safe battery technologies relies on the replacement of liquid electrolytes with a fast ion conductor that does not combust. We report a novel nitride interface modifier by coating the garnet-type Li6.25Al0.25La3Zr2O12 (Al-LLZO) solid electrolyte with a thin layer of Si3N4 deposited by radio frequency (RF) sputtering technique. This interfacial buffer layer enabled establishment of a homogeneous and intimate physical contact between the SSE and Li0. With optimization of the Si3N4@Al-LLZO interfacial layer, Li/Si3N4@Al-LLZO/LFP full cells showed excellent overall cycling and rate performance
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