FeOCl Nanoparticle-Embedded Mesocellular Carbon Foam as a Cathode Material with Improved Electrochemical Performance for Chloride-Ion Batteries

Chloride-ion batteries (CIBs) have been regarded as a promising alternative battery technology to lithium-ion batteries because of their abundant resources, high theoretical volumetric energy density, and high safety. However, the research on chloride-ion batteries is still in its infancy. Exploring appropriate cathode materials with desirable electrochemical performance is in high demand for CIBs. Herein, the FeOCl nanocrystal embedded in a mesocellular carbon foam (MCF) has been prepared and developed as a high-performance cathode material for CIBs. The MCF with uniform and large mesocells (15.7–31.2 nm) interconnected through uniform windows (15.2–21.5 nm) can provide high-speed pathways for electron and chloride-ion transport and accommodate the strain caused by the volume change of FeOCl during cycling. As a result, the optimized FeOCl@MCF cathode exhibits the highest discharge capacity of 235 mAh g–1 (94% of the theoretical capacity) among those of the previously reported metal (oxy)­chloride cathodes for CIBs. A reversible capacity of 140 mAh g–1 after 100 cycles is retained. In contrast, only 18 mAh g–1 was kept for the FeOCl cathode

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

Electrosorption-promoted Photodegradation of Opaque Wastewater on A Novel TiO₂/Carbon Aerogel Electrode

A novel electrosorption-photocatalysis synergistic electrode of TiO2/carbon aerogel (TiO2/CA) is prepared. The thermal stability and dispersion of the anatase TiO2 particles are well facilitated by the porous and discontinuous microstructure of CA. The degradation experiments show that the TiO2/CA material is not only a good photocatalyst but also an excellent electrosorptive electrode. The TiO2/CA is easily molded to an agglomerate electrode. The opaque wastewater with dyestuff is degraded effectively by the electrosorption-promoted photocatalytic process on this electrode. For the simulated methylene blue (MB) wastewater (150 mg L−1), the rate constant of MB degradation in the electro-assisted photocatalytic process with the conventional ITO-supported TiO2 (TiO2/ITO) is 0.55 × 10−3 min−1 and that the electrosorption-promoted photocatalysis with TiO2/CA is 10.27 × 10−3 min−1, which is 18 times the former. In the electrosorption-promoted photocatalytic process with TiO2/CA, the energy consumption removing per unit TOC is only 15% of that in the electro-assisted photocatalysis with TiO2/ITO, because the electrosorption is a nonfaradic process irrelative to any electron transfer and requires very low consumption. This study provides a new method for exploring highly efficient electrosorption-promoted photocatalytics technology in the treatment of opaque wastewater

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

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

Sulfonated Bacterial Cellulose-Based Functional Gel Polymer Electrolyte for Li–O₂ Batteries with LiI as a Redox Mediator

The practical applications of Li–O2 batteries are hindered by the large charge polarization. Recently, the development of redox mediators (RMs) brings new hope for constructing low overpotential Li–O2 batteries. However, the “shuttle effect” of RMs causes new problems. Here, based on a low-cost and environmentally friendly biomaterial–bacterial cellulose, a sulfonation strategy was adopted to produce a functional gel polymer electrolyte for LiI-involved Li–O2 batteries. Benefiting from the high-density negatively charged sulfonate groups on the sulfonated bacterial cellulose, the functionalized gel electrolyte can produce strong electrostatic repulsion force to the negatively charged I3– ions to suppress the shuttle effect. As a result, the Li–O2 battery shows a good cycling performance with eliminated self-discharge, and the Li anode is successfully protected by the inhibition of I3– shuttling. This novel approach may provide new insights into the development of functionalized gel polymer electrolytes for Li–O2 batteries with redox mediators

In Situ Partial Pyrolysis of Sodium Carboxymethyl Cellulose Constructing Hierarchical Pores in the Silicon Anode for Lithium-Ion Batteries

Silicon is an attractive anode material for the high-energy-density lithium-ion battery due to its high theoretical capacity (4200 mA h g–1). However, larger volume expansion (∼300%) and pulverization during cycling hinder the commercialization of silicon anodes. The modification of silicon materials is a widely recognized approach to enhance the anode performance, but the volume expansion cannot be solved completely when only focusing on the active material but ignoring the overall structural optimization of the anode. In the study, additional hierarchical pores were constructed in the electrodes by in situ partial pyrolysis of the binder sodium carboxymethyl cellulose (CMC) at low temperature. Benefiting from the extra buffer space, the electrodes can accommodate more expansion and enhance the conduction of electrons and ions. In addition, the partially degraded CMC reduced the adsorption energy between the binder and the active material, reducing the stress during the swelling process, which is demonstrated by density functional theory. The as-obtained electrode delivered a high reversible capacity of 1035 mA h g–1 at 1000 mA g–1, while the capacity retention was 78.7%, and the Coulombic efficiency was stable at 99.3% after 200 cycles. The modification of the electrode structure provides guidance for the construction of high-efficiency anodes

Pulse-Assisted Low-Temperature Sintering to Enhance the Fast-Charging Capability for P2-Layered Na-Based Cathodes

Utilizing an anionic redox reaction for charge compensation is a promising breakthrough in boosting the energy density of P2-layered Na-based cathodes. However, sluggish kinetics and irreversible surface oxygen loss cause poor rate performance and severe capacity degradation, plaguing the practical fast-charging cathode application for sodium-ion batteries. Herein, a pulse-assisted low-temperature sintering strategy is first proposed to alleviate the above obstacles successfully. First, the primary particles are optimized with minor size and less agglomeration. Further analysis via a series of in situ and ex situ characterizations reveals the generation of surface oxygen vacancies, which facilitate the electrochemical kinetics and induce a robust spinel-like protective film. The synergistic effect suppresses the irreversible oxygen release and unfavorable interfacial reactions and improves the structural integrity and electrochemical kinetics in prolonged cycling. Consequently, the optimized cathode of P2-type Na0.72Li0.24Mn0.76O2 shows a splendid cycle life of 130.5 mA h g–1 after 100 cycles at 200 mA g–1 and excellent rate capacity of 107.9 mA h g–1 at 1000 mA g–1 in the voltage range of 1.5–4.5 V. The full cell is assembled with a presodiation anode, which delivers a promising energy density (∼485.2 W h kg–1, 1.0–4.4 V). Another practical asset stems from its low-energy consumption through a low-temperature sintering process. Overall, this work offers a guiding significance to enhance the electrochemical kinetics and fast-charging capability for sodium–Mn-based oxide cathodes with anionic redox