RESUMEN
The next generation of high-energy-density storage devices is expected to be rechargeable lithium metal batteries. However, unstable metal-electrolyte interfaces, dendrite growth, and volume expansion will compromise lithium metal batteries (LMB) safety and life. A simple drop-casting method is used to create a double-layer functional interface composed of inorganic mesoporous TiO2 and F-rich organics PFDMA. For high-quality lithium deposition, TiO2 can provide uniform mechanical pressure, abundant mesoporous channels, and increased ionic conductivity, while PFDMA provides enough F to form LiF in the first cycle and improves Li-electrolyte compatibility. Experiments and simulations are combined to investigate the optimized mechanism of the LiF-rich solid electrolyte interface (SEI). The high binding energy of organic matter and Li demonstrates that Li+ preferentially binds with the F atom in organic matter. As a result, the tightly bound double-layer structure can inhibit lithium dendrite growth and slow electrolyte decomposition. Consequently, the symmetric Li||Li cell has a high stability performance of over 800 h. The assembled LiFePO4 ||Li cell can sustain 300 cycles at a 1 C rate and has a reversible capacity of 136.7 mAh g-1 .
RESUMEN
High-energy-density Li-metal batteries are of great significance in the energy storage field. However, the safety hazards caused by Li dendrite growth and flammable organic electrolytes significantly hinder the widespread application of Li-metal batteries. In this work, we report a highly safe electrolyte composed of 4 M lithium bis(fluorosulfonyl)imide (LiFSI) dissolved in the single solvent trimethyl phosphate (TMP). By regulating the solvation structure of the electrolyte, a combination of nonflammability and Li dendrite growth suppression was successfully realized. Both Raman spectroscopy and molecular dynamics simulations revealed improved dendrite-free Li anode originating from the unique solvation structure of the electrolyte. Symmetric Li/Li cells fabricated using this nonflammable electrolyte had a long cycle life of up to 1000 h at a current density of 0.5 mA cm-2. Furthermore, the Li4Ti5O12/TMP-4/Li full cells also exhibited excellent cycling performance with a high initial discharge capacity of 170.5 mAh g-1 and a capacity retention of 92.7% after 200 cycles at 0.2 C. This work provides an effective approach for the design of safe electrolytes with favorable solvation structure toward the large-scale application of Li-metal batteries.
RESUMEN
To attain both high energy density and power density in sodium-ion (Na+ ) batteries, the reaction kinetics and structural stability of anodes should be improved by materials optimization. In this work, few-layered molybdenum sulfide selenide (MoSSe) consisting of a mixture of 1T and 2H phases is designed to provide high ionic/electrical conductivities, low Na+ diffusion barrier, and stable Na+ storage. Reduced graphene oxide (rGO) is used as a conductive matrix to form 3D electron transfer paths. The resulting MoSSe@rGO anode exhibits high capacity and rate performance in both organic and solid-state electrolytes. The ultrafast Na+ storage kinetics of the MoSSe@rGO anode is attributed to the surface-dominant reaction process and broad Na+ channels. In situ and ex situ measurements are conducted to reveal the Na+ storage process in MoSSe@rGO. It is found that the MoS and MoSe bonds effectively limit the dissolution of the active materials. The favorable Na+ storage kinetics of the MoSSe@rGO electrode are ascribed to its low adsorption energy of -1.997 eV and low diffusion barrier of 0.087 eV. These results reveal that anion doping of metal sulfides is a feasible strategy to develop sodium-ion batteries with high energy and power densities and long life-span.
