Suppressing Self-Discharge of Vanadium Diboride by Zwitterionicity of the Polydopamine Coating Layer

The vanadium boride (VB2) air battery is currently known as a primary battery with the highest theoretical specific capacity, 4060 mA h g–1, which originates from an extraordinary 11 electrons per VB2 molecule oxidation process. However, the parasitical reaction between VB2 and hydroxide ions in the alkaline electrolyte leads to obvious self-discharge, which results in severe capacity loss during discharge. In this work, we applied the polydopamine (PDA) membrane to modify the surface of VB2 particles, which contains amine groups and phenolic hydroxyl groups exhibiting fully reversible, pH-switchable permselectivity. The “smart” membrane with pH-switching characteristics successfully coordinated the conflict between the electrolyte and VB2 in the open circuit to avoid corrosion but also ensured that the hydroxide ions can enter the VB2 particle surface to participate in the reaction during discharge. According to the corrosion suppression test, the remaining amount of VB2@PDA is 90 wt % stored at 65 °C for 2 weeks, which is 10 wt % more than the uncoated VB2. The assembled pouch cell with the VB2@PDA anode can deliver a high capacity of 325 mA h at 250 mA g–1, retaining an improved Coulombic efficiency of 86.3%, which is 18.7% higher than that of the cell with the raw VB2 anode. Moreover, the 0.05 V higher discharge voltage of the VB2@PDA-based cell further shows that the PDA membrane can effectively conduct hydroxide ions during discharge

Trimethylsilyl Chloride-Modified Li Anode for Enhanced Performance of Li–S Cells

A facile and effective method to modify Li anode for Li–S cells by exposing Li foils to tetrahydrofuran (THF) solvent, oxygen atmosphere and trimethylsilyl chloride ((CH₃)₃SiCl) liquid in sequence is proposed. The results of SEM and XPS show the formation of a homogeneous and dense film with a thickness of 84 nm on Li metal surface. AC impedance and polarization test results show the improved interfacial stability. The interfacial resistances as well as polarization potential difference have obviously decreased as compared with that of a pristine Li anode. CV and charge–discharge test results demonstrate that more reversible discharge capacity and higher Coulombic efficiency can be achieved. Specific capacity of 760 mAh g^–1 and an average Coulombic efficiency of 98% are retained after 100 cycles at 0.5<i>C</i> without LiNO₃ additive. Additionally, the Li–S cell with a modified Li anode displays a greatly improved rate performance with ∼425 mAh g^–1 at 5<i>C</i>, making it more attractive and competitive in the applications of high-power supply

Cobalt-Metal-Based Cathode for Lithium–Oxygen Battery with Improved Electrochemical Performance

Metal-oxide-based free-standing cathodes for Li–O2 batteries have been widely reported due to the high stability and catalytic activity of metal oxides. Herein, we present a novel cobalt-metal-based free-standing cathode for Li–O2 battery. By replacing the metal-oxide catalysts with cobalt metal, the conductivity of the electrode was improved. On the other hand, the oxide layer on the surface of metal particles could still act as an effective catalyst during cell operation. Consequently, the metal-based electrodes delivered high discharge capacity with relatively low overpotential. A long battery life with 160 cycles was also achieved

Long-Lifespan Lithium Metal Batteries Enabled by a Hybrid Artificial Solid Electrolyte Interface Layer

Lithium metal batteries based on metallic Li anodes have been recognized as competitive substitutes for current energy storage technologies due to their exceptional advantage in energy density. Nevertheless, their practical applications are greatly hindered by the safety concerns caused by lithium dendrites. Herein, we fabricate an artificial solid electrolyte interface (SEI) via a simple replacement reaction for the lithium anode (designated as LNA-Li) and demonstrate its effectiveness in suppressing the formation of lithium dendrites. The SEI is composed of LiF and nano-Ag. The former can facilitate the horizontal deposition of Li, while the latter can guide the uniform and dense lithium deposition. Benefiting from the synergetic effect of LiF and Ag, the LNA-Li anode exhibits excellent stability during long-term cycling. For example, the LNA-Li//LNA-Li symmetric cell can cycle stably for 1300 and 600 h at the current densities of 1 and 10 mA cm–2, respectively. Impressively, when matching with LiFePO4, the full cells can steadily cycle for 1000 times without obvious capacity attenuation. In addition, the modified LNA-Li anode coupled with the NCM cathode also exhibits good cycling performance

Construction of High-Strength Flame-Retardant Li-SPEEK-Modified PEG Gel Polymer Electrolytes for Lithium Batteries

The low mechanical performance and high flammability of gel polymer electrolytes limit their application. Here, we prepare a high-strength and nonflammable polymer Li-SPEEK (lithium sulfonated polyetheretherketone) to modify PEG (polyethylene glycol) and construct a PEG-Li-SPEEK cross-linked network as a polymer electrolyte matrix, with an overall improvement in electrochemical performance, mechanical properties, and flame retardancy. The PEG-Li-SPEEK-ls (PEG-Li-SPEEK cross-linked network after gelation of the liquid electrolyte) electrolyte achieves a conductivity of 1.62 × 10–4 S·cm–1 at 30 °C, a wider electrochemical window of 4.5 V vs Li+/Li, and a higher lithium-ion transference number compared to the PEG-ls electrolyte. The excellent mechanical properties allow the symmetric cell-containing PEG-Li-SPEEK-ls electrolyte to exhibit better cycling performance for over 300 h at a current density of 0.2 mA·cm–2. The LFP/PEG-Li-SPEEK-ls/Li cells deliver a maximum discharge capacity of 142.1 mAh·g–1 with a capacity retention of 98.1% after 50 cycles at 0.5 C and the Coulombic efficiency remains above 99.5% throughout the cycling process. In addition, the good carbon formation properties of Li-SPEEK give the electrolyte matrix satisfactory flame-retardant properties. Thus, we validate the excellent performance of Li-SPEEK for modifying conventional polymer electrolytes and improving their mechanical, electrochemical, and flame-retardant properties