Toward High-Energy-Density Initial-Anode-Free Lithium-Metal Batteries via Ultra-Thin Protective Ion-Transport-Promoting Interface Modification and Surface Prelithiation.

Anode-free lithium-metal batteries (AFLMBs) are desirable candidates for achieving high-energy-density batteries, while severe active Li+ loss and uneven Li plating/stripping behavior impede their practical application. Herein, a trilaminar LS-Cu (LiCPON + Si/C-Cu) current collector is fabricated by radio frequency magnetron sputtering, including a Si/C hybrid lithiophilic layer and a supernatant carbon-incorporated lithium phosphorus oxynitride (LiCPON) solid-state electrolyte layer. Joint experimental and computational characterizations and simulations reveal that the LiCPON solid-state electrolyte layer can decompose into an in situ stout ion-transport-promoting protective layer, which can not only regulate homogeneous Li plating/stripping behavior but also inhibit the pulverization and deactivation of Si/C hybrid lithiophilic layer. When combined with surface prelithiated Li1.2Ni0.13Co0.13Mn0.54O2 (Preli-LRM) cathode, the Preli-LRM||LS-Cu full cell delivers 896.1 Wh kg-1 initially and retains 354.1 Wh kg-1 after 50 cycles. This strategy offers an innovative design of compensating for active Li+ loss and inducing uniform Li plating/stripping behavior simultaneously for the development of AFLMBs.

Monitoring Hot Holes in Plasmonic Catalysis on Silver Nanoparticles by Using an Ion Label.

Energetic carriers generated by localized surface plasmon resonance (LSPR) provide an efficient way to drive chemical reactions. However, their dynamics and impact on surface reactions remain unknown due to the challenge in observing hot holes. This makes it difficult to correlate the reduction and oxidation half-reactions involving hot electrons and holes, respectively. Here we detect hot holes in their chemical form, Ag(I), on a Ag surface using surface-enhanced Raman scattering (SERS) of SO32- as a hole-specific label. It allows us to determine the dynamic correlations of hot electrons and holes. We find that the equilibrium of holes is the key factor of the surface chemistry, and the wavelength-dependent plasmonic chemical anode refilling (PCAR) effect plays an important role, in addition to the LSPR, in promoting the electron transfer. This method paves the way for visualizing hot holes with nanoscale spatial resolution toward the rational design of a plasmonic catalytic platform.

Phosphorized 3D Current Collector for High-Energy Anode-Free Lithium Metal Batteries.

The anode-free lithium metal battery (AF-LMB) demonstrates the emerging battery chemistry, exhibiting higher energy density than the existing lithium-ion battery and conventional LMB empirically. A systematic step-by-step while bottom-up calculation system is first developed to quantitatively depict the energy gap from theory to practice. The attainable high energy of AF-LMB necessitates a homogeneous Li+ flux on the anode side to achieve an improved Li reversibility against inventory loss. On such basis, a lithiophilic Cu3P-decorated 3D copper foil to promote dendrite-free lithium deposition is further reported. The phosphorized surface of high affinity toward Li+ incorporating the nanostructure of abundant nucleation sites synergistically regulates the Li nucleation/growth behavior, extending the cycling lifespan of high-loading AF-LMBs. The processed foil featuring lightweight and ultrathin merits further increases the energy density, both gravimetrically and volumetrically. This study provides a novel scheme for simultaneously realizing the uniform deposition of lithium and increasing the energy density of future AF-LMBs.

Multifunctional Interface Layer Constructed by Trace Zwitterions for Highly Reversible Zinc Anodes.

The inhomogeneous plating/stripping of Zn anode, attributed to dendrite growth and parasitic reactions at the electrode/electrolyte interface, severely restricts its cycling life-span. Here, trace zwitterions (trifluoroacetate pyridine, TFAPD) are introduced into the aqueous electrolyte to construct a multifunctional interface that enhances the reversibility of Zn anode. The TFA- anions with strong specific adsorption adhere onto the Zn surface to reconstruct the inner Helmholtz plane (IHP), preventing the hydrogen evolution and corrosion side reactions caused by free H2O. The Py+ cations accumulate on the outer Helmholtz plane (OHP) of Zn anode with the force of electric field during Zn2+ plating, forming a shielding layer to uniformize the deposition of Zn2+. Besides, the adsorbed TFA- and Py+ promote the desolvation process of Zn2+ resulting in fast reaction kinetics. Thus, the Zn||Zn cells present an outstanding cycling performance of more than 10000 hours. And even at 85% utilization rate of Zn, it can stably cycle for over 200 hours at 10 mA cm-2 and 10 mAh cm-2. The Zn||I2 full cell exhibits a capacity retention of over 95% even after 30000 cycles. Remarkably, the Zn||I2 pouch cells (95 mAh) deliver a high-capacity retention of 99% after 750 cycles.

Modulating Interfacial Zn2+ Desolvation and Transport Kinetics through Coordination Interaction toward Stable Anodes in Aqueous Zn-Ion Batteries.

Aqueous Zn-ion batteries (AZIBs) are promising candidates for grid-scale energy-storage applications, but uneven Zn2+ flux distribution and undesirable water-related interfacial side reactions seriously hinder their practical application. Herein, a strategy of regulating the coordination interaction between Zn2+ and artificial interphase layers (AILs) to modulate the interfacial Zn2+ desolvation/transport behaviors and relieve side reactions for building stable Zn anodes is proposed. By selectively choosing appropriate polymers with different functional groups, it is shown that compared with the strong interaction offered by aryl groups in polystyrene-based AILs, cyano groups in polyacrylonitrile (PAN)-based AILs provide a moderate coordination interaction with Zn2+, which not only accelerates interfacial Zn2+desolvation kinetics but also enables efficient Zn2+ transport within AILs. Moreover, the Zn2+ transport kinetics of PAN-based AILs can be further enhanced with the incorporation of an ionic conductor, zinc phosphate (ZP). Because of these advantages, the Zn anodes decorated with the hybrid AILs composed of PAN and ZP can steadily operate for >2000 h at 0.2 mA cm-2 and >350 h at a high current density of 10 mA cm-2. This work provides a valuable guideline for selective design of AILs at the molecular level for durable AZIBs.

Biocathode-anode cascade system in PRB: Efficient degradation of p-chloronitrobenzene in groundwater.

The consistent presence of p-chloronitrobenzene (p-CNB) in groundwater has raised concerns regarding its potential harm. In this study, we developed a biocathode-anode cascade system in a permeable reactive barrier (BACP), integrating biological electrochemical system (BES) with permeable reactive barrier (PRB), to address the degradation of p-CNB in the groundwater. BACP efficiently accelerated the formation of biofilms on both the anode and cathode using the polar periodical reversal method, proving more conducive to biofilm development. Notably, BACP demonstrated a remarkable p-CNB removal efficiency of 94.76 % and a dechlorination efficiency of 64.22 % under a voltage of 0.5 V, surpassing the results achieved through traditional electrochemical and biological treatment processes. Cyclic voltammetric results highlighted the primary contributing factor as the synergistic effect between the bioanode and biocathode. It is speculated that this system primarily relies on bioelectrocatalytic reduction as the predominant process for p-CNB removal, followed by subsequent dechlorination. Furthermore, electrochemical and microbiological tests demonstrated that BACP exhibited optimal electron transfer efficiency and selective microbial enrichment ability under a voltage of 0.3-0.5 V. Additionally, we investigated the operational strategy for initiating BACP in engineering applications. The results showed that directly introducing BACP technology effectively enhanced microbial film formation and pollutant removal performance.

Rational Design of Quasi-1D Multicore-Shell MnSe@N-Doped Carbon Nanorods as High-Performance Anode Material for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are considered one of the promising candidates for energy storage devices due to the low cost and low redox potential of sodium. However, their implementation is hindered by sluggish kinetics and rapid capacity decay caused by inferior conductivity, lattice deterioration, and volume changes of conversion-type anode materials. Herein, we report the design of a multicore-shell anode material based on manganese selenide (MnSe) nanoparticle encapsulated N-doped carbon (MnSe@NC) nanorods. Benefiting from the conductive multicore-shell structure, the MnSe@NC anodes displayed prominent rate capability (152.7 mA h g-1 at 5 A g-1) and long lifespan (132.7 mA h g-1 after 2000 cycles at 5 A g-1), verifying the essence of reasonable anode construction for high-performance SIBs. Systematic in situ microscopic and spectroscopic methods revealed a highly reversible conversion reaction mechanism of MnSe@NC. Our study proposes a promising route toward developing advanced transition metal selenide anodes and comprehending electrochemical reaction mechanisms toward high-performance SIBs.

Anode glow discharge electrolysis synthesis of flower-like α-MnO2 nanospheres: structure, formation mechanism, and supercapacitor performance.

A novel green synthesis strategy-anode glow discharge electrolysis (AGDE) was employed for one-step preparation of a-MnO2 in 2 g L-1 KMnO4 solution, in which Pt needle and carbon rod were regarded as anode and cathode, respectively. The optimal preparation condition is 400 V for 60 min and the power consumption is below 45 W. The XRD, Raman spectra, XPS and EPR proved that a-MnO2 with structural defects (oxygen vacancies) is obtained. SEM and TEM revealed that a-MnO2 shows a flower-like nanospheres with a diameter of 165 nm, which is assembled by many nanosheets. A possible formation mechanism is that the MnO2 is generated via the reduction of MnO4- by H· and eaq- in plasma-liquid interface. Electrochemical test found that MnO2 nanospheres exhibit a specific capacitance of 365 F g-1 at 1 A g-1, and capacity retention of 79.8% after 10,000 cycles at 5 A g-1. The assembled asymmetric supercapacitor shows the maximum energy density of 23.1 Wh kg-1 at power density of 1.89 kW kg-1. In brief, AGDE is a simple, facile and green technique for the synthesis of a-MnO2 without adding extra chemicals, and prepared a-MnO2 can be considered as an excellent candidate of electrode materials for supercapacitor.

Anode potential regulates gas composition and microbiome in anaerobic electrochemical digestion.

Anaerobic electrochemical digestion (AED) is an effective system for recovering biogas from organic wastes. However, the effects of different anode potentials on anaerobic activated sludge remain unclear. This study confirmed that biofilms exhibited the best electroactivity at -0.2 V (vs. Ag/AgCl) compared to -0.4 V and 0 V. Gas was further regulated, with the highest hydrogen content (47 ±â€¯7 %) observed at -0.2 V. The 0 V system produced the largest amount of methane (70 ±â€¯8 %) and exhibited the greatest presence of hydrogen-utilizing microorganisms. The gas yield at -0.4 V was the lowest, with no hydrogen detected. Excess bioelectrohydrogen at -0.2 V and 0 V caused the co-enrichment of Methanobacterium and Acetoanaerobium, establishing a thermodynamically feasible current-acetate-hydrogen electron cycle to improve electrogenesis. These results provide insights into the regulatory strategies of MEC technology during anaerobic digestion, which play a decisive role in determining the composition of biogas.

Scale Construction of "Breathing" Bi/N-CNSs Quasi-Array Structure with Hierarchical Bi Distribution for Sodium-Ion Battery.

Sodium ion batteries (SIBs) are promising postlithium battery technologies with high safety and low cost. However, their development is hampered by complicated electrode material preparation and unsatisfactory sodium storage performance. Here, a bismuth/N-doped carbon nanosheets (Bi/N-CNSs) composite featuring a quasi-array structure (alternated porous Bi layers and N-CNSs) with hierarchical Bi distribution (large particles of ∼35 nm in Bi layers and ultrafine Bi of ∼8 nm on N-CNSs) is prepared. Bi/N-CNSs delivers an ultralong-lifespan of 26000 cycles at 5 A g-1 and prominent rate capability of 91.5% capacity retention at 100 A g-1. Even at -40 °C, it exhibits a high rate capability of 161 mAh g-1 at 5 A g-1. Notably, the involved preparation method is characterized by a high yield of 14.53 g in a single laboratory batch, which can be further scaled up, and such a method can also be extended to synthesize other metallic-based materials.

Sieving-type Electric Double Layer with Hydrogen Bond Interlocking to Stable Zinc Metal Anode.

The stability of aqueous zinc metal batteries is significantly affected by side reactions and dendrite growth on the anode interface, which primarily originate from water and anions. Herein, we introduce a multi H-bond site additive, 2, 2'-Sulfonyldiethanol (SDE), into an aqueous electrolyte to construct a sieving-type electric double layer (EDL) by hydrogen bond interlock in order to address these issues. On the one hand, SDE replaces H2O and SO42- anions that are adsorbed on the zinc anode surface, expelling H2O/SO42- from the EDL and thereby reducing the content of H2O/SO42- at the interface. On the other hand, when Zn2+ are de-solvated at the interface during the plating, the strong hydrogen bond interaction between SDE and H2O/SO42- can trap H2O/SO42- from the EDL, further decreasing their content at the interface. This effectively sieves them out of the zinc anode interface and inhibits the side reactions. Moreover, the unique characteristics of trapped SO42- anions can restrict their diffusion, thereby enhancing the transference number of Zn2+ and promoting dendrite-free deposition and growth of Zn. Consequently, utilizing an SDE/ZnSO4 electrolyte enables excellent cycling stability in Zn//Zn symmetrical cells and Zn//MnO2 full cells with lifespans exceeding 3500 h and 2500 cycles respectively.

High-Performance Sodium-Ion Batteries with Graphene: An Overview of Recent Developments and Design.

Due to their low production cost, sodium-ion batteries (SIBs) are considered attractive alternatives to lithium-ion batteries (LIBs) for next generation sustainable and large-scale energy storage systems. However, during the charge/discharge cycle, a large volume strain is resulted due to the presence of a large radius of sodium ions and high molar compared to lithium ions, which further leads to poor cyclic stability and lower reversible capacity. Hence, as a promising anode material for SIBs, the two-dimensional (2D) materials including graphene and its derivatives and metal oxides have attracted remarkable attention due to their layered structure and superior physical and chemical properties. The inclusion of graphene and metal oxides with other nanomaterials in electrodes have led to the significant enhancements in electrical conductivity, reaction kinetics, capacity, rate performance and accommodating the large volume change respectively. In this review article, the fabrication techniques, structural configuration, sodium ion storage mechanism and its electrochemical performances will be introduced. Subsequently, an insight into the recent advancements in SIBs associated with 2D anode materials (graphene, graphene oxide (GO), transition metal oxides etc.) and other graphene-like elementary analogues (germanene, stanine etc.) as anode materials respectively will be discussed.

Internal cycling of Fe3+/Fe2+ within Fe3O4 on cathode promotes green degradation of reactive brilliant red X-3B on anode.

Reactive brilliant red X-3B (RBRX-3B) wastewater is difficult to decolourise, not readily biodegradable, and large in quantity. Therefore, the efficient removal of RBRX-3B is crucial. In this paper, a green and efficient electrochemical-electro-Fenton system with Fe3O4-modified carbon felt bag cathode (ECEF-Fe3O4) was set up to degrade RBRX-3B wastewater. Experiments confirmed that the removal of RBRX-3B by ·OH or H2O2 is quite low, and RBRX-3B can be completely oxidised and degraded directly on the anode. Long-cycle experimental data further shows that the degradation efficiency of RBRX-3B on the anode is 100% at 70 min at the reaction rate constants (k) of 0.071 min-1 in ECEF-Fe3O4 while that of RBRX-3B on the cathode is only 16.8 ± 0.9%. The generation of ·OH is mainly catalysed through the internal cycling of Fe3+/Fe2+ within Fe3O4 on the cathode, and the generation and annihilation of ·OH on the cathode enhance the oxidation efficiency of the anode, achieving the green and effective removal of RBRX-3B by the anode in ECEF-Fe3O4.

Supramolecular Metal-Organic Framework for the High Stability of Aqueous Rechargeable Zinc Batteries.

Aqueous rechargeable Zn batteries (AZBs) are considered to be promising next-generation battery systems. However, the growth of Zn dendrites and water-induced side reactions have hindered their practical application, especially with regard to long-term cyclability. To address these challenges, we introduce a supramolecular metal-organic framework (SMOF) coating layer using an α-cyclodextrin-based MOF (α-CD-MOF-K) and a polymeric binder. The plate-like α-CD-MOF-K particles, combined with the polymeric binder create dense and homogeneous Zn2+ ion conductive pore channels that can vertically transport Zn2+ ions through the cavity while restricting the contact of water molecules. Molecular dynamics (MD) simulation verifies that Zn2+ ions can reversibly migrate through the pores of α-CD-MOF-K by partial dehydration. The uniform Zn deposition/dissolution promotes a smooth solid-electrolyte interface layer on the Zn metal anode and effectively suppresses side reactions with free water molecules. The α-CD-MOF-K@Zn symmetric cell exhibits stable cycling and a small polarization voltage of 70 mV for 800 h at 5 mA cm-2, and the α-CD-MOF-K@Zn|α-MnO2 full cell shows only 0.12% capacity decay per cycle at a rate of 1 A g-1.

Improvements and Challenges of Hydrogel Polymer Electrolytes for Advanced Zinc Anodes in Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) are widely regarded as desirable energy storage devices due to their inherent safety and low cost. Hydrogel polymer electrolytes (HPEs) are cross-linked polymers filled with water and zinc salts. They are not only widely used in flexible batteries but also represent an ideal electrolyte candidate for addressing the issues associated with the Zn anode, including dendrite formation and side reactions. In HPEs, an abundance of hydrophilic groups can form strong hydrogen bonds with water molecules, reducing water activity and inhibiting water decomposition. At the same time, special Zn2+ transport channels can be constructed in HPEs to homogenize the Zn2+ flux and promote uniform Zn deposition. However, HPEs still face issues in practical applications, including poor ionic conductivity, low mechanical strength, poor interface stability, and narrow electrochemical stability windows. This Review discusses the issues associated with HPEs for advanced AZIBs, and the recent progresses are summarized. Finally, the Review outlines the opportunities and challenges for achieving high performance HPEs, facilitating the utilization of HPEs in AZIBs.

Theoretical Investigation of a Novel Two-Dimensional Non-MXene Mo3C2 as a Prospective Anode Material for Li- and Na-Ion Batteries.

A new two-dimensional (2D) non-MXene transition metal carbide, Mo3C2, was found using the USPEX code. Comprehensive first-principles calculations show that the Mo3C2 monolayer exhibits thermal, dynamic, and mechanical stability, which can ensure excellent durability in practical applications. The optimized structures of Lix@(3×3)-Mo3C2 (x = 1-36) and Nax@(3×3)-Mo3C2 (x = 1-32) were identified as prospective anode materials. The metallic Mo3C2 sheet exhibits low diffusion barriers of 0.190 eV for Li and 0.118 eV for Na and low average open circuit voltages of 0.31-0.55 V for Li and 0.18-0.48 V for Na. When adsorbing two layers of adatoms, the theoretical energy capacities are 344 and 306 mA h g-1 for Li and Na, respectively, which are comparable to that of commercial graphite. Moreover, the Mo3C2 substrate can maintain structural integrity during the lithiation or sodiation process at high temperature. Considering these features, our proposed Mo3C2 slab is a potential candidate as an anode material for future Li- and Na-ion batteries.

Synthesis and Characterisation of Nanocrystalline CoxFe1-xGDC Powders as a Functional Anode Material for the Solid Oxide Fuel Cell.

The necessity for high operational temperatures presents a considerable obstacle to the commercial viability of solid oxide fuel cells (SOFCs). The introduction of active co-dopant ions to polycrystalline solid structures can directly impact the physiochemical and electrical properties of the resulting composites including crystallite size, lattice parameters, ionic and electronic conductivity, sinterability, and mechanical strength. This study proposes cobalt-iron-substituted gadolinium-doped ceria (CoxFe1-xGDC) as an innovative, nickel-free anode composite for developing ceramic fuel cells. A new co-precipitation technique using ammonium tartrate as the precipitant in a multi-cationic solution with Co2+, Gd3+, Fe3+, and Ce3+ ions was utilized. The physicochemical and morphological characteristics of the synthesized samples were systematically analysed using a comprehensive set of techniques, including DSC/TGA for a thermal analysis, XRD for a crystallographic analysis, SEM/EDX for a morphological and elemental analysis, FT-IR for a chemical bonding analysis, and Raman spectroscopy for a vibrational analysis. The morphological analysis, SEM, showed the formation of nanoparticles (≤15 nm), which corresponded well with the crystal size determined by the XRD analysis, which was within the range of ≤10 nm. The fabrication of single SOFC bilayers occurred within an electrolyte-supported structure, with the use of the GDC as the electrolyte layer and the CoO-Fe2O3/GDC composite as the anode. SEM imaging and the EIS analysis were utilized to examine the fabricated symmetrical cells.

LaMnO3-Type Perovskite Nanofibers as Effective Catalysts for On-Cell CH4 Reforming via Solid Oxide Fuel Cells.

CH4 has become the most attractive fuel for solid oxide fuel cells due to its wide availability, narrow explosion limit range, low price, and easy storage. Thus, we present the concept of on-cell reforming via SOFC power generation, in which CH4 and CO2 can be converted into H2 and the formed H2 is electrochemically oxidized on a Ni-BZCYYb anode. We modified the porosity and specific surface area of a perovskite reforming catalyst via an optimized electrostatic spinning method, and the prepared LCMN nanofibers, which displayed an ideal LaMnO3-type perovskite structure with a high specific surface area, were imposed on a conventional Ni-BZCYYb anode for on-cell CH4 reforming. Compared to LCMN nanoparticles used as on-cell reforming catalysts, the NF-SOFC showed lower ohmic and polarization resistances, indicating that the porous nanofibers could reduce the resistances of fuel gas transport and charge transport in the anode. Accordingly, the NF-SOFC displayed a maximum power density (MPD) of 781 mW cm-2 and a stable discharge voltage of around 0.62 V for 72 h without coking in the Ni-BZCYYb anode. The present LCMN NF materials and on-cell reforming system demonstrated stability and potential for highly efficient power generation with hydrocarbon fuels.

Constructing Three-Dimensional Architectures to Design Advanced Copper-Based Current Collector Materials for Alkali Metal Batteries: From Nanoscale to Microscale.

Alkali metals (Li, Na, and K) are deemed as the ideal anode materials for next-generation high-energy-density batteries because of their high theoretical specific capacity and low redox potentials. However, alkali metal anodes (AMAs) still face some challenges hindering their further applications, including uncontrollable dendrite growth and unstable solid electrolyte interphase during cycling, resulting in low Coulombic efficiency and inferior cycling performance. In this regard, designing 3D current collectors as hosts for AMAs is one of the most effective ways to address the above-mentioned problems, because their sufficient space could accommodate AMAs' volume expansion, and their high specific surface area could lower the local current density, leading to the uniform deposition of alkali metals. Herein, we review recent progress on the application of 3D Cu-based current collectors in stable and dendrite-free AMAs. The most widely used modification methods of 3D Cu-based current collectors are summarized. Furthermore, the relationships among methods of modification, structure and composition, and the electrochemical properties of AMAs using Cu-based current collectors, are systematically discussed. Finally, the challenges and prospects for future study and applications of Cu-based current collectors in high-performance alkali metal batteries are proposed.

Boosting bioelectricity generation in bioelectrochemical systems with nitrogen-doped three-dimensional graphene aerogel anode.

Bioelectricity generation by electrochemically active bacteria has become particularly appealing due to its vast potential in energy production, pollution treatment, and biosynthesis. However, developing high-performance anodes for bioelectricity generation remains a significant challenge. In this study, a highly efficient three-dimensional nitrogen-doped macroporous graphene aerogel anode with a nitrogen content of approximately 4.38 ± 0.50 at% was fabricated using hydrothermal method. The anode was successfully implemented in bioelectrochemical systems inoculated with Shewanella oneidensis MR-1, resulting in a significantly higher anodic current density (1.0 A/m2) compared to the control one. This enhancement was attributed to the greater biocapacity and improved extracellular electron transfer efficiency of the anode. Additionally, the N-doped aerogel anode demonstrated excellent performance in mixed-culture inoculated bioelectrochemical systems, achieving a high power density of 4.2 ± 0.2 W/m², one of the highest reported for three-dimensional carbon-based bioelectrochemical systems to date. Such improvements are likely due to the good biocompatibility of the N-doped aerogel anode, increased extracellular electron transfer efficiency at the bacteria/anode interface, and selectively enrichment of electroactive Geobacter soli within the NGA anode. Furthermore, based on gene-level Picrust2 prediction results, N-doping significantly upregulated the conductive pili-related genes of Geobacter in the three-dimensional anode, increasing the physical connection channels of bacteria, and thus strengthening the extracellular electron transfer process in Geobacter.