RESUMEN
The construction of carbon-encapsulated transition metal nanotube structures is a preferred method that can effectively slow down volume expansion, improve cycling stability and enhance the electrical conductivity of the reactive sites of lithium-ion batteries. In this study, nanotubes of carbon-coated NiCo-NiCo2O4 nanoparticles (NC-NCO@C) were prepared by a one-step molten salt method at high temperature using Ni and Co as catalytic centers and sodium acetate as carbon source. We used NC-NCO@C-2 nanotubes as anode materials for lithium-ion batteries(LIBs), which exhibited excellent lithium storage performance and good stability, with a specific capacity of 616.26 mAh g-1 after 1000 cycles at a high current density of 1 A g-1. In addition, NC-NCO@C-2 were used as anodes in lithium-ion full cells and LiFePO4 (LFP) was used as the cathode. The NC-NCO@C-2//LFP full-cell exhibits high capacity and good cycling stability, with a capacity of 100.7 mAh g-1 after 100 cycles and a capacity retention rate of 92%. The construction of NC, NCO, and carbon ternary complexes was found to activate and promote the reversible conversion of certain inorganic components at the solid electrolyte interfaces (SEI), which effectively reduced the volume change during cycling, increased the electrical conductivity, and improved the cycling stability of the electrode. The proposed one-step molten salt synthesis of Carbon-coated metals complexes with excellent compatibility characteristics, is expected to solve the problem of volume change in transition metals, which is encountered in LIBs applications.
RESUMEN
HIGHLIGHTS: A novel amide-based nonflammable electrolyte is proposed. The formation mechanism and solvation chemistry are investigated by molecular dynamics simulations and density functional theory. An inorganic/organic-rich solid electrolyte interphase with an abundance of LiF, Li3N and Li-N-C is in situ formed, leading to spherical lithium deposition. The amide-based electrolyte can enable stable cycling performance at room temperature and 60 â. The formation of lithium dendrites and the safety hazards arising from flammable liquid electrolytes have seriously hindered the development of high-energy-density lithium metal batteries. Herein, an emerging amide-based electrolyte is proposed, containing LiTFSI and butyrolactam in different molar ratios. 1,1,2,2-Tetrafluoroethyl-2,2,3,3-tetrafluoropropylether and fluoroethylene carbonate are introduced into the amide-based electrolyte as counter solvent and additives. The well-designed amide-based electrolyte possesses nonflammability, high ionic conductivity, high thermal stability and electrochemical stability (> 4.7 V). Besides, an inorganic/organic-rich solid electrolyte interphase with an abundance of LiF, Li3N and Li-N-C is in situ formed, leading to spherical lithium deposition. The formation mechanism and solvation chemistry of amide-based electrolyte are further investigated by molecular dynamics simulations and density functional theory. When applied in Li metal batteries with LiFePO4 and LiMn2O4 cathode, the amide-based electrolyte can enable stable cycling performance at room temperature and 60 â. This study provides a new insight into the development of amide-based electrolytes for lithium metal batteries.
RESUMEN
Small molecule organic acids as electrode materials possess the advantages of high theoretical capacity, low cost, and good processability. However, these electrode materials suffer from poor cycling stability due to the inevitable dissolution of organic molecules in the electrolytes. Here, a eutectic mixture of lithium bis(trifluoromethanesulfonyl)imide and N-methylamine is employed as a eutectic electrolyte in Li-ion batteries with small molecule organic acids as electrodes. To enhance the cycling stability of the electrolyte, fluoroethylene carbonate is used as an additive. The electrolyte exhibits nonflammability, high ionic conductivity, and good electrochemical stability. Molecular dynamics simulations and density functional theory are performed to further investigate the solvation chemistry of the eutectic electrolyte. The well-designed eutectic electrolyte inhibits the dissolution of terephthalic acid effectively and displays superior performance with a capacity retention of ≈84% after 2000 cycles at a high current density of 1 A g-1 . It also enables stable cycling of more than 900 cycles at a high current density of 2 A g-1 at 60 °C. This study provides a strategy to enhance the cycling stability and safety of Li-ion batteries with organic electrode materials.
