Rational Design of an Artificial SEI: Alloy/Solid Electrolyte Hybrid Layer for a Highly Reversible Na and K Metal Anode

In-Depth Understanding of Interfacial Na+ Behaviors in Sodium Metal Anode: Migration, Desolvation, and Deposition

Interfacial Na+ behaviors of sodium (Na) anode severely threaten the stability of sodium-metal batteries (SMBs). This review systematically and in-depth discusses the current fundamental understanding of interfacial Na+ behaviors in SMBs including Na+ migration, desolvation, diffusion, nucleation, and deposition. The key influencing factors and optimization strategies of these behaviors are further summarized and discussed. More importantly, the high-energy-density anode-free sodium metal batteries (AFSMBs) are highlighted by addressing key issues in the areas of limited Na sources and irreversible Na loss. Simultaneously, recent advanced characterization techniques for deeper insights into interfacial Na+ deposition behavior and composition information of SEI film are spotlighted to provide guidance for the advancement of SMBs and AFSMBs. Finally, the prominent perspectives are presented to guide and promote the development of SMBs and AFSMBs.

A Critical Review on Room-Temperature Sodium-Sulfur Batteries: From Research Advances to Practical Perspectives

Room-temperature sodium-sulfur (RT-Na/S) batteries are promising alternatives for next-generation energy storage systems with high energy density and high power density. However, some notorious issues are hampering the practical application of RT-Na/S batteries. Besides, the working mechanism of RT-Na/S batteries under practical conditions such as high sulfur loading, lean electrolyte, and low capacity ratio between the negative and positive electrode (N/P ratio), is of essential importance for practical applications, yet the significance of these parameters has long been disregarded. Herein, it is comprehensively reviewed recent advances on Na metal anode, S cathode, electrolyte, and separator engineering for RT-Na/S batteries. The discrepancies between laboratory research and practical conditions are elaborately discussed, endeavors toward practical applications are highlighted, and suggestions for the practical values of the crucial parameters are rationally proposed. Furthermore, an empirical equation to estimate the actual energy density of RT-Na/S pouch cells under practical conditions is rationally proposed for the first time, making it possible to evaluate the gravimetric energy density of the cells under practical conditions. This review aims to reemphasize the vital importance of the crucial parameters for RT-Na/S batteries to bridge the gaps between laboratory research and practical applications.

Unraveling the Nucleation and Growth Mechanism of Potassium Metal on 3D Skeletons for Dendrite-Free Potassium Metal Batteries

Designing three-dimensional (3D) porous carbonaceous skeletons for K metal is one of the most promising strategies to inhibit dendrite growth and enhance the cycle life of potassium metal batteries. However, the nucleation and growth mechanism of K metal on 3D skeletons remains ambiguous, and the rational design of suitable K hosts still presents a significant challenge. In this study, the relationships between the binding energy of skeletons toward K and the nucleation and growth of K are systematically studied. It is found that a high binding energy can effectively decrease the nucleation barrier, reduce nucleation volume, and prevent dendrite growth, which is applied to guide the design of 3D current collectors. Density functional theory calculations show that P-doped carbon (P-carbon) exhibits the highest binding energy toward K compared to other elements (e.g., N, O). As a result, the K@P-PMCFs (P-binding porous multichannel carbon nanofibers) symmetric cell demonstrates an excellent cycle stability of 2100 h with an overpotential of 85 mV in carbonate electrolytes. Similarly, the perylene-3,4,9,10-tetracarboxylic dianhydride || K@P-PMCFs cell achieves ultralong cycle stability (85% capacity retention after 1000 cycles). This work provides a valuable reference for the rational design of 3D current collectors.

Advances in Electrochemical Energy Storage over Metallic Bismuth-Based Materials

Bismuth (Bi) has been prompted many investigations into the development of next-generation energy storage systems on account of its unique physicochemical properties. Although there are still some challenges, the application of metallic Bi-based materials in the field of energy storage still has good prospects. Herein, we systematically review the application and development of metallic Bi-based anode in lithium ion batteries and beyond-lithium ion batteries. The reaction mechanism, modification methodologies and their relationship with electrochemical performance are discussed in detail. Additionally, owing to the unique physicochemical properties of Bi and Bi-based alloys, some innovative investigations of metallic Bi-based materials in alkali metal anode modification and sulfur cathodes are systematically summarized for the first time. Following the obtained insights, the main unsolved challenges and research directions are pointed out on the research trend and potential applications of the Bi-based materials in various energy storage fields in the future.

Oxygen Defect Engineering toward Zero-Strain V2O2.8@Porous Reticular Carbon for Ultrastable Potassium Storage

Potassium-ion batteries (KIBs) are promising candidates for large-scale energy storage devices due to their high energy density and low cost. However, the large potassium-ion radius leads to its sluggish diffusion kinetics during intercalation into the lattice of the electrode material, resulting in electrode pulverization and poor cycle stability. Herein, vanadium trioxide anodes with different oxygen vacancy concentrations (V2O2.9, V2O2.8, and V2O2.7 determined by the neutron diffraction) are developed for KIBs. The V2O2.8 anode is optimal and exhibits excellent potassium storage performance due to the realization of expanded interlayer spacing and efficient ion/electron transport. In situ X-ray diffraction indicates that V2O2.8 is a zero-strain anode with a volumetric strain of 0.28% during the charge/discharge process. Density functional theory calculations show that the impacts of oxygen defects are embodied in reducing the band gap, increasing electron transfer ability, and lowering the diffusion energy barriers for potassium ions. As a result, the electrode of nanosized V2O2.8 embedded in porous reticular carbon (V2O2.8@PRC) delivers high reversible capacity (362 mAh g-1 at 0.05 A g-1), ultralong cycling stability (98.8% capacity retention after 3000 cycles at 2 A g-1), and superior pouch-type full-cell performance (221 mAh g-1 at 0.05 A g-1). This work presents an oxygen defect engineering strategy for ultrastable KIBs.

Enhancing Interfacial Strength and Wettability for Wide-Temperature Sodium Metal Batteries

Development of high-performance sodium metal batteries (SMBs) with a wide operating temperature range (from -40 to 55 °C) is highly challenging. Herein, an artificial hybrid interlayer composed of sodium phosphide (Na3 P) and metal vanadium (V) is constructed for wide-temperature-range SMBs via vanadium phosphide pretreatment. As evidenced by simulation, the VP-Na interlayer can regulate redistribution of Na+ flux, which is beneficial for homogeneous Na deposition. Moreover, the experimental results confirm that the artificial hybrid interlayer possesses a high Young's modulus and a compact structure, which can effectively suppress Na dendrite growth and alleviate the parasitic reaction even at 55 °C. In addition, the VP-Na interlayer exhibits the capability to knock down the kinetic barriers for fast Na+ transportation, realizing a 30-fold decrease in impedance at -40 °C. Symmetrical VP-Na cells present a prolonged lifespan reaching 1200, 500, and 500 h at room temperature, 55 °C and -40 °C, respectively. In Na3 V2 (PO4 )3 ||VP-Na full cells, a high reversible capacity of 88, 89.8, and 50.3 mAh g-1 can be sustained after 1600, 1000, and 600 cycles at room temperature, 55 °C and -40 °C, respectively. The pretreatment formed artificial hybrid interlayer proves to be an effective strategy to achieve wide-temperature-range SMBs.

High-Crystallinity BiOCl Nanosheets as Efficient Photocatalysts for Norfloxacin Antibiotic Degradation

Semiconductor photocatalysts are essential materials in the field of environmental remediation. Various photocatalysts have been developed to solve the contamination problem of norfloxacin in water pollution. Among them, a crucial ternary photocatalyst, BiOCl, has attracted extensive attention due to its unique layered structure. In this work, high-crystallinity BiOCl nanosheets were prepared using a one-step hydrothermal method. The obtained BiOCl nanosheets showed good photocatalytic degradation performance, and the degradation rate of highly toxic norfloxacin using BiOCl reached 84% within 180 min. The internal structure and surface chemical state of BiOCl were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, Fourier transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance (UV-vis), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectra (XPS), and photoelectric techniques. The higher crystallinity of BiOCl closely aligned molecules with each other, which improved the separation efficiency of photogenerated charges and showed high degradation efficiency for norfloxacin antibiotics. Furthermore, the obtained BiOCl nanosheets possess decent photocatalytic stability and recyclability.