Journal
JOURNAL OF MATERIALS CHEMISTRY A
Volume 11, Issue 35, Pages 18984-18995Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/d3ta03543c
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Li2OHCl is a promising solid-state electrolyte for all-solid-state Li-ion batteries. Strain engineering, achieved through isovalent doping, can improve Li+ conductivity and stabilize the highly conductive cubic phase at room temperature. By introducing tensile strain, Li2OHCl0.921I0.079 achieves a significantly higher ionic conductivity and demonstrates enhanced battery performance compared to Li2OHCl.
Li2OHCl is a promising solid-state electrolyte (SSE) for all-solid-state Li-ion batteries thanks to its simple synthesis and low precursor costs. However, its low ionic conductivity is a challenge for its use in devices. This study employs density functional theory (DFT) calculations to investigate the effect of strain on Li+ transport, showing that the migration energy barrier decreases if tensile strain is applied. In practice, such strain can be obtained by isovalent doping, i.e., by substituting Cl with larger I and Br atoms. Further DFT calculations and experiments show that tensile strain not only enhances conductivity but also stabilizes the highly conductive cubic phase at room temperature. An optimized composition (i.e., Li2OHCl0.921I0.079) reaches an ionic conductivity of 0.50 mS cm-1 at 373 K, which is five times larger than that of Li2OHCl at the same temperature. Furthermore, a Li/Li2OHCl0.921I0.079/Li symmetric cell can cycle for more than 800 h, and a Li/Li2OHCl0.921I0.079/LiFePO4 battery achieves 50% capacity retention after 274 cycles with significantly enhanced performance compared to Li2OHCl. These findings highlight the potential of strain engineering to enhance the conductivity of SSEs and motivate further research on designing fast ion conductors. Introducing the tensile strain can improve the Li+ conductivity and simultaneously stabilize the cubic phase at low temperatures.
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