ABSTRACT
Solid-state electrolyte (SSE) of the sodium-ion battery have attracted tremendous attention in the next generation energy storage materials on account of their wide electrochemical window and thermal stability. However, the high interfacial impedance, low ion transference number and complex preparation process restrict the application of SSE. Herein, inspired by the excellent sieving function and high specific surface area of red blood cells, we obtained a solid-like electrolyte (SLE) based on the combination of the pancake-like metal-organic framework (MOF) with liquid electrolyte, possessing a high ionic conductivity of 6.60 × 10-4 S cm-1, and excellent sodium metal compatibility. In addition, we investigated the ion restriction effect of MOF's apertures size and special functional groups, and the ion transference number increased from 0.16 to 0.33. Finally, the assembled Na0.44MnO2//SLE//Na full batteries showed no obvious capacity decrease after 160 cycles. This material design of SLE in our work is an important key to obtain fast ion migration SLE for high-performance sodium-ion batteries.
ABSTRACT
Composite solid electrolytes (CSEs) hold great promise toward safe lithium metal batteries with high energy density, due to integration of the merits of polymer matrixes and fillers. Rational design of filler nanostructures has attracted increasing attention for improving the ionic transport of CSEs in solid batteries. In this work, we fabricated open-structured Li0.33La0.557TiO3 (LLTO) nanotubes (NTs) as ion-conductive fillers in CSEs by a gradient electrospinning method for the first time. Different from nanoparticles (NPs) and nanowires (NWs), our nanotubes are composed of connected small NPs, which offer three-dimensional (3D) Li+-accessible pathways, large polymer/filler interfacial ionic conduction regions, and enhanced wettability against the polymer matrix. As a result, the solid electrolytes based on LLTO NTs and polyacrylonitrile (PAN) can display a high ionic conductivity of up to 3.6 × 10-4 S cm-1 and a wide electrochemical window of 5 V at room temperature (RT). Furthermore, Li-Li symmetric cells using the LLTO NTs/PAN CSE can work stably over 1000 h with a polarization of 20 mV. LiFePO4-Li full cells exhibit a high capacity of 142.5 mAh g-1 with a capacity retention of 90% at 0.5 C after 100 cycles. All of these results demonstrate that the design of open-structured nanotubes as fillers is a promising strategy for high-performance solid electrolytes.
ABSTRACT
Enabling stable lithium metal anodes is significant for developing electrochemical energy storage systems with higher energy density. However, safety hazards, infinite volume expansion, and low coulombic efficiency (CE) of lithium metal anodes always hinder their practical application. Herein, a nano-thickness lithiophilic Cu-Ni bimetallic coating was synthesized to prepare dendrite-free lithium metal anodes. The electron cloud migration effect caused by the different electronegativities of Cu and Ni can achieve lithiophobicity/lithiophilicity transformation and thus promote uniform Li deposition/dissolution. By changing the ratio of Cu to Ni, the electron cloud migration can be reasonably adjusted for obtaining dendrite-free lithium anodes. As a result, the as-obtained Cu-Ni bimetallic coating is able to guarantee dendrite-free lithium metal anodes with a stable long cycling time (>1500 hours) and a small voltage hysteresis (â¼26 mV). In addition, full cells with LiFePO4 as a cathode present excellent cycling stability and high coulombic efficiency. This work can open a new avenue for optimizing the lithiophilicity of materials and realizing dendrite-free anodes.
ABSTRACT
Inverse gas chromatographic (IGC) technology was used to determine the solubility parameters of three asymmetrical dicationic ionic liquids ([ PyC5Pi] [ NTf2]2, [MpC5Pi] [NTf2]2 and [PyC6Pi] [NTf2]2) at 343.15-363.15 K. Five alkanes were applied as test probes including octane (n-C8) , decane (n-C10), dodecane (n-C12), tetradecane (n-C14), hexadecane (n-C16). Some thermodynamic parameters were obtained by IGC data analysis, such as the specific retention volumes of the solvents (V0(g)), the molar enthalpies of sorption (ΔHs(1)), the partial molar enthalpies of mixing at infinite dilution (ΔH∞91)), the molar enthalpies of vaporization (ΔH)v)), the activity coefficients at infinite dilution (Ω∞(1)), and Flory-Huggins interaction parameters (χ∞(12)) between ionic liquids and probes. The solubility parameters (δ2) of the three dicationic ionic liquids at room temperature (298.15 K) were 28.52-32.66 (J x cm(-3)) ½. The solubility parameters (δ2) of cationic structure with 4-methyl morpholine are bigger than those of the cationic structure with pyridine. The bigger the solubility parameter (δ2) is, the more the carbon numbers of linking group of the ionic liquids are. The results are of great importance to the study of the solution behavior and the applications of ionic liquid.
