Ni-rich layered cathode materials have been intensively explored to maximize the energy density of lithium-ion batteries (LIBs). However, their performance is compromised by unstable surface reactions in the high-voltage region, resulting in detrimental changes to the surface structure. In this study, an effective strategy to improve the long-term stability of LIBs is demonstrated. This strategy involves conformally wrapping two-dimensional (2D) molybdenum disulfide (MoS2) nanosheets on Ni-rich layered cathodes via electrostatic interactions between positively surface-treated MoS2 and negatively charged cathode particles. The formation of MoS2 wrapping layers prevents direct interfacial contact between the cathode and the electrolyte, thereby preventing surface-triggered structural degradation and unwanted side reactions. The improved cell stability was verified, with advantages including reduced gas evolution, facile Li-ion transfer, and mitigated microcrack propagation. This 2D material-wrapping strategy allows for thin and effective coverage of the cathode surface, consequently ensuring improved safety and longer lifespans for LIBs.

The increasing demand for Li-ion batteries across various energy storage applications underscores the urgent need for environmentally friendly and efficient direct recycling strategies to address the issue of substantial cathode waste. Diverse reducing agents for Li supplements, such as quinone molecules, have been considered to homogenize the Li distribution in the cathode materials obtained after cycling; however, the detailed reaction mechanism is still unknown. Herein, the ideal electrochemical potential factor and reaction mechanism of the redox mediator 3,5-di-tert-butyl-o-benzoquinone (DTBQ) for the chemical relithiation of high-Ni-layered cathodes are elucidated. Here, 100% efficiency of DTBQ-assisted chemical relithiation is achieved by adjusting the direct immersion time of Li-deficient cathode electrodes. The reversible reaction features of the physical and chemical structures of both the regenerated cathodes and the DTBQ molecules are investigated using advanced characterization and density functional theory calculations. These findings emphasize the potential of redox-mediator-assisted chemical relithiation for realizing direct recycling processes and offer a facile and sustainable solution for battery recycling.

The efficient evolution of gaseous hydrogen and oxygen from water is required to realize sustainable energy conversion systems. To address the sluggish kinetics of the multielectron transfer reaction, bifunctional catalyst materials for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) should be developed. Herein, a tailored combination of atomically minimized iridium catalysts and highly conductive black WO3- x nanofiber supports are developed for the bifunctional electrolyzer system. Atomic Ir catalysts, particularly those that activate the OER, minimize the utilization of precious metals. The oxygen-deficient black WO3- x NF support, which boosts the HER, offers increased electronic conductivity and favorable nucleation sites for Ir loading. The Ir-black WO3- x NFs exhibit increased double-layer capacitance, a significantly reduced onset potential, lower Tafel slope, and stable cyclability for both the OER and HER, compared to large-sized Ir catalysts loaded on white WO3 nanofibers. This study offers a strategy for developing an optimal catalyst material with suitable supports for high-performance and economical water electrolysis systems for achieving carbon-negative targets.

Sodium metal batteries (SMBs) have been considered as one of the most favorable and economic candidates for next generation batteries to overcome low enenrgy density limitation of sodium ion batteries (SIBs) due to high theoretical specific capacity (1166 mAh g-1), low electrochemical redox potential (-2.71 V vs. SHE). However, ‘moss-like’ dendrite growth that occurs during continuous charging and discharging processes not only threatens the safety of batteries, but also poses several problems to be solved, such as electrolyte consumption, hugh volume expansion, dead Na formation, and low coulombic efficiency. The dendrite problem in the SMBs is similr to that of lithium-metal batteries (LMBs), yet the degree of the issue is further severe than LMBs. Surface stabilization of sodium metal anode should be achieved to realize SMB technologies. The introduction of functional electrolyte additives is an effective and economical way to overcome these problems and improve the cyclability of SMBs. Based on the similarity between electroplating and sodium deposition reaction, utilization of surface leveler additive in the electrolyte could allow a substantial impact to stabilize sodium metal surface during repeated deposition and stripping process. In this presentation, we confirmed the surface flattening effect of molecular dipole electrolyte additives at the anode through the Na-Na symmetric cell test. Sodium metal deposition and stripping behavior has been successfully controlled by introducing surface leveler additives for realization of SMBs. Even under rapid charging and discharging situations, additive containing Na-Na symmetric cells showed stable performance for over 2000 hours, which is 5 times longer than the pristine cell without the additive. We confirmed that controlling intrinsic properties of surface leveler additive can effectively further improve cycle performance of SMBs. [1] S.-Y. Jun, K. Shin, C. Y. Son, J. Park, H.-S. Kim, J.-Y. Hwang, W.-H. Ryu, Advanced Energy Materials, 2024, 2304504 [2] S.-Y. Jun, K. Shin, Y. Lim, S. Kim, H. Kim, C. Y. Son, W.-H. Ryu, Small Structures, 2024, 5, 2300578 [3] S.-Y. Jun, K. Shin, J.-S. Lee, S. Kim, J. Chun, W.-H. Ryu, Advanced Science, 2023, 10, 2301426 [4] J.-S. Lee, K. Shin, S.-Y. Jun, S. Kim, W.-H. Ryu, Chemical Engineering Journal, 2023, 458, 141383 Figure 1

The conformal surface coating of Ni-rich layered cathode materials is essential for mitigating their interfacial and subsequent structural degradation. The zirconia (ZrO2) coating effectively enhances the surface stability of the cathode owing to its excellent chemical durability; however, the insulating electrical conductivity of ZrO2 increases the electrode resistance and triggers efficiency decay. Here, we propose highly conductive oxygen-deficient black ZrO2-x as a charge-conductive coating material. The black ZrO2-x is uniformly coated onto the Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC) surface via a solvent-free mechanochemical shearing process. Benefiting from the black ZrO2-x coating layer, black ZrO2-x coated NMC shows improved cycling characteristics and better rate capability than both bare NMC and ZrO2 coated NMC. The enhanced electrochemical performance by the conformal coating of black ZrO2-x mainly results from enhanced charge transfer, reduced gas evolution, and mitigated microstructural cracking. Density functional theory calculations confirm that the defective structure of black ZrO2-x lowers the energy barrier for Li ion transfer, and strong hybridization between Zr in black ZrO2-x and O in NMC mitigates oxygen evolution. Black ZrO2-x is coated onto a Ni-rich cathode via solvent-free shearing, enhancing charge transfer, reducing gas evolution, and preventing cracking. It lowers Li-ion transfer barriers and mitigates oxygen release through strong Zr-O hybridization.

Lithium-oxygen (Li-O2) batteries are an emerging energy storage alternative with the potential to meet the recent increase in demand for high-energy-density batteries. From a practical viewpoint, lithium-air (Li-Air) batteries using ambient air instead of pure oxygen could be the final goal. However, the slow oxygen reduction and evolution reactions interfere with reversible cell operation during cycling. Therefore, research continues to explore various catalyst materials. The present study attempts to improve the performance of Li-Air batteries by using porphyrin-based materials known to have catalytic effects in Li-O2 batteries. The results confirm that the iron phthalocyanine (FePc) catalyst not only exhibits a catalytic effect in an air atmosphere with a low oxygen fraction but also suppresses electrolyte decomposition by stabilizing superoxide radical ions (O2-) at a high voltage range. Density functional theory calculations are used to gain insight into the exact FePc-mediated catalytic mechanism in Li-Air batteries, and various ex situ and in situ analyses reveal the reversible reactions and structural changes in FePc during electrochemical reaction. This study provides a practical solution to ultimately realize an air-breathing battery using nature-friendly catalyst materials. Iron phthalocyanines (FePcs) as a promising bifunctional electrocatalyst are employed in different atmospheric environments using O2 and air-breathing cells for high performance and suppression of side reactions (electrolyte decomposition) in the high voltage range. By using FePc, it simultaneously promotes the battery reaction and suppresses the electrolyte decomposition in the high voltage range (over 4.0 V). Also, when FePc is used in an air atmosphere, O2 and CO2 competitively bind with the central metal of FePc and proceed with the reaction. image

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Lithium metal batteries (LMBs) have been recognized as high-energy storage alternatives; however, problematic surface reactions due to dendritic Li growth are major obstacles to their widespread utilization. Herein, a 3-mercapto-1-propanesulfonic acid sodium salt (MPS) with asymmetrically functionalized thiol and sulfonate groups as polarizable interface-restructuring molecules is proposed to achieve rapid and longer-operating LMBs. Under a harsh condition of 5 mA cm-2, Li-Li symmetric cells employing MPS can be cycled over 1200 cycles, outperforming those employing other molecules symmetrically functionalized by thiol or sulfonate groups. The improved performance of the Li|V2O5 full cell is demonstrated by introducing MPS additives. MPS additives offer advantages by flattening the surface, reconfiguring Li nucleation and growth along the stable (110) plane, and forming a durable and conductive solid-electrolyte interface layer (SEI). This study suggests an effective way to develop a new class of electrolyte additives for LMBs by controlling engineering factors, such as functional groups and polarizable properties.

Abundant and economical sodium (Na) metal batteries promise superior energy densities compared to lithium-ion batteries; however, they face commercialization challenges owing to problematic interfacial reactions leading to dendrite formation during cycling. This paper reports the ultra-long and rapid operation of Na metal batteries enabled by the introduction of a vinylpyrrolidone (VP)-based multifunctional interface stabilizer in the electrolyte. The VP electrolyte additive provides benefits such as surface flattening, durable solid electrolyte interphase layer formation, preservation of fresh Na, and acceleration of horizontal crystal growth along the (110) plane. Symmetric Na-Na cells with the stabilizer exhibit notably stable operation for over 5 000 cycles at a high current density of 5 mA cm-2, surpassing previous research. Performance improvement is also demonstrated in a full-cell configuration with an Na3V2(PO4)2O2F cathode. This approach offers a promising solution for achieving performance levels comparable to lithium-ion batteries in Na metal battery technology. Na-metal batteries offer exceptional energy merits comparable to existing Li-ion batteries, yet problematic dendrite formation and unstable surface side reactions on the Na anode must be addressed. The ultra-long and rapid operating performance is achieved in Na-metal batteries by introducing polarizable vinylpyrrolidone molecules dissolved in the electrolyte as a surface-flattening and interface-stabilizing additive. image

To overcome the energy limitations of conventional Li‐ion batteries (LIB), renewed attention has been given to Li‐metal anodes, which provide the highest capacity and lowest anode potential. To realize Li‐metal batteries (LMBs), it is crucial to stabilize unwanted side reactions on the surface and to inhibit problematic dendrite growth, which causes short‐circuit issues. Herein, diverse pyrrolidone‐based molecular dipole additives controlled by different functional groups are introduced as trifunctional surface stabilizers. It is discovered that the Li–Li symmetric cell improves proportionally with the molar volume and corresponding polarizability values of the molecular dipoles. The highly polarizable pyrrolidone‐based molecular dipoles offer exceptional benefits, including surface flattening of the Li metal anode, controlling the growth direction of crystalline Li, and forming durable solid electrolyte interface (SEI) components. The study is based on polarizability‐controlled molecular dipoles, and offers an effective approach for designing advanced surface stabilizers to develop of high‐performance LMBs.

Expediting electrochemical reactions that involve gaseous components is crucial for the development of diverse energy and environmental applications (batteries, electrochemical conversion, fuel cells, and gas sensors). Unfortunately, the intrinsically closed structure of conventional electrochemical cell systems, in which a liquid (or solid) electrolyte exists between the electrodes, does not allow the facile and direct diffusion of gaseous reactants or products to/from the electrode surface. Our design, an electrochemical cell system with an open-structured form factor, involves an "aeroelectrolyte" that floats in the air and directly approaches the electrode surfaces. The electrochemical system contains a nonwoven nanofiber salt bridge to ensure continuous and stable electrochemical reactions in the aeroelectrolyte-based cells. We confirmed the feasibility of our design in a modified Daniell cell by varying the factors that affect the aeroelectrolyte and electrode components. Our open-structure electrochemical system with the aeroelectrolyte enables the realization of ideal three-phase boundaries for atmospheric electrochemical reactions. We propose an open-structured electrochemical cell system as a new form factor featuring an "aeroelectrolyte" that floats in the air and directly engages with the electrode surfaces.

Lithium-oxygen (Li-O2) batteries, recognized as candidates for the highest energy storage, face challenges of irreversibility and low efficiency due to insulating discharge products. Addressing these issues, our study explores innovative...

Layered cathode materials have advanced existing Li-ion batteries by improving cell voltage and enabling facile charge transfer. Yet diverse synthetic issues such as particle inhomogeneity, Li residues, complicated processes, and large micron-scale particle sizes, need to be addressed. We report a direct solution-calcination strategy for the simple and scalable synthesis of layered cathode materials (i.e. LiCoO2) for Li-ion batteries. Polyvinylpyrrolidone (PVP) as functional agent is introduced to intimately bind and uniformize the metal precursors, thereby sufficiently eliminating surface Li residues and forming a uniform particle distribution. Compared with commercial LCO, solution-calcined LCO exhibits improved cycling stability and rate capability with suppressed phase transition. The structural phase evolution mechanism for solution-calcination is investigated using in-situ X-ray diffraction analysis. Overall, our research suggests a simple and versatile strategy for the synthesis of cathode materials; the proposed method is effective and avoids complicated synthesis steps and the formation of unwanted residual lithium compounds.

Li-CO2 batteries involve a spontaneous conversion reaction by injecting CO2 into a cathode, and reversibly store energy without additional energy input through a charging and discharging process, thereby achieving carbon neutrality. Noble metal-based electrocatalysts have been actively considered to efficiently facilitate the Li-CO2 reaction with reduced overvoltage, yet the use of expensive noble metal catalysts is a barrier to developing this type of Li-CO2 battery. Here, the importance of minimizing the size of noble metal particle-based catalysts for Li-CO2 batteries is reviewed and emphasized. Comparisons of the performance of Li-CO2 cells with noble metal catalysts, such as Ru and Ir, showed that overpotential is lower when particle sizes are reduced to the single atom-scale. This indicates that the smaller the particle-to-atomic scale, the greater the catalytic activity. Recent diverse studies based on nano- or atomic-scale Ru and Ir catalysts affecting catalytic activities of the Li-CO2 cell reaction are introduced. Other single atom catalyst candidates are also suggested for Li-CO2 battery applications.

Lithium‑oxygen batteries (LOBs) have attracted considerable attention as promising high energy density batteries. One of the common reasons for LiO2 cell failure is the collapse of the free-standing electrode owing to inadequate mechanical stability, resulting in a battery with poor cycle life. It remains challenging to prepare structurally stable electrode materials to enable long and efficient operation of batteries. Herein, we report three-dimensional hierarchical carbon nanotubes/graphene (CNTs/Gr) bundles as mechanically durable free-standing electrodes for high-performance LOBs. We introduce a novel chemical vapor deposition method for fabricating CNTs foam that can be grown on Fe catalyst seeds embedded in the graphite intercalation compound (FeCl3-GIC). The inner CNTs act as pillars between graphene layers to absorb compressive forces, ensuring excellent mechanical strength. In addition, countless CNTs blooms grown from graphene layers provide numerous reaction sites for LiO2 reaction. The hierarchical CNTs/Gr bundles exhibit 100% mechanical recovery properties and 5–6 times better electrochemical cyclability than the reference CNTs bundles without graphene. This new structure and fabrication strategy could provide a new approach to prepare high-performance carbon-based free-standing electrode alternatives.

Fluoride-based conversion reaction electrode materials offer exceptional theoretical capacity merit for Na-ion batteries. Nevertheless, it has rarely been considered as potential anode material candidate due to (i) excessive redox potential (> 3 V) and (ii) intrinsically low reaction kinetics related to sluggish structural reorganization process. In this work, we demonstrate that chiolite Na5Ti3F14/carbon nanocomposite can deliver the outstanding electrochemical performances as the promising anode for Na-ion batteries, such as a large specific capacity of similar to 425 mAh g(-1) at 10 mA g(-1) with a low average operating voltage, the capacity retention of similar to 78 % compared to the initial capacity after 300 cycle with a high Coulombic efficiency of above 99 %, etc. We demonstrate that the chiolite Na5Ti3F14 phase can store the similar to 8.33 mol Na ions through the following conversion reaction; Na5Ti3F14 + 9Na + 9e(-) double left right arrow 3Ti + 14NaF, which is clearly confirmed by various ex-situ analyses using Xray diffraction, synchrotron-based X-ray adsorption spectroscopy, etc. We expect that this research can provide guidance toward the development of a new class of low-cost and high-performance anode materials, not only for Na-ion batteries but also for other rechargeable batteries.

Lithium-ion batteries (LIBs) and beyond-LIB systems exhibit properties that are determined by electrochemical reactions occurring in their four essential components-the cathode, anode, electrolyte, and separator. Advanced analytical methods such as differential electrochemical mass spectrometry (DEMS) can assist in understanding the electrochemical behavior, which can help in advancing battery technologies. Recent studies have shown that the DEMS-enabled real-time gas analysis of electrochemical reactions can provide valuable information on aspects such as gaseous reactants or (side) products, which cannot be obtained appropriately through other characterization techniques. This review aims to provide a comprehensive overview of the latest developments and advancements in the use of DEMS as a rapid, operando gas-monitoring method for advanced rechargeable battery systems. Moreover, the significance of DEMS in current and future battery development is also discussed and insights are provided into the various battery chemistries that can benefit from DEMS applications. This review is intended to help readers understand the potential of DEMS to drive innovation in the battery industry.

Anode-free Li-metal batteries have been reported to maximize the volumetric energy density in the cell by excluding the thick anode component while taking advantage of the high energy benefit of Li-metal anode. Nevertheless, irregular Li dendrite growth and unstable surface reactions impede the practical application of anode-free Li-metal batteries. Herein, we report a "Li-dendrite cage" for a promising anode-free Li-metal battery configuration employing a three-dimensionally (3-D) interconnected porous Cu foam electrode synthesized by a facile and versatile electrodeposition method. The numerous pores within the electrode serve as "cages" to accommodate Li dendrites for Li deposition, consequently suppressing the vertical growth of Li and alleviating the volume change of the cell during cycling. The 3-D interconnected porous Cu foam electrode exhibits facile charge transfer, lower nucleation overpotential, and reduced polarization compared to conventional Cu foil. We also investigate the Li plating/stripping behaviors and morphology evolution on the unique 3-D interconnected porous Cu foam electrode by cross-sectional observations and ex-situ characterizations. This work provides a novel strategy for rationally designing porous electrodes to achieve stable and high performance of anode-free Li-metal batteries.

Surface modification of cathodes using Ni-rich coating layers prevents bulk and surface degradation for the stable operation of Li-ion batteries at high voltages. However, insulating and dense inorganic coating layers often impede charge transfer and ion diffusion kinetics. In this study, the fabrication of dual functional coating materials using metal-organic polyhedra (MOP) with 3D networks within microporous units of Li-ion batteries for surface stabilization and facile ion diffusion is proposed. Zr-based MOP is modified by introducing acyl groups as a chemical linkage (MOPAC), and MOPAC layers are homogenously coated by simple spray coating on the cathode. The coating allow the smooth transport of electrons and ions. MOPAC effectively suppress side reactions between the cathode and electrolyte and protect active materials against aggressive fluoride ions by forming a Li-ion selective passivation film. The MOPAC-coated Ni-rich layered cathode exhibited better cycle retention and enhanced kinetic properties than pristine and MOP-coated cathodes. Reduction of undesirable gas evolution on the cathode by MOPAC is also verified. Microporous MOPAC coating can simultaneously stabilize both the bulk and surface of the Ni-rich layered cathode and maintain good electrochemical reaction kinetics for high-performance Li-ion batteries.