High-nickel layered cathodes, such as NCM811, promise high energy density for next-generation lithium-ion batteries but suffer from interfacial degradation, irreversible capacity loss, and transition metal dissolution under high-voltage operation. Here, a sacrificial silyl ketone additive, bis(di-tert-butylmethylsilyl) ketone, (MetBu2Si)2CO, is introduced to simultaneously modulate cathode-electrolyte interphase (CEI) formation and suppress parasitic reactions. (MetBu2Si)2CO undergoes preferential oxidation during the first cycle, forming a selflimiting, thin, and uniform protective layer while scavenging HF, as evidenced by Si 2p XPS and 19F NMR studies. Furthermore, in situ XRD reveals that (MetBu2Si)2CO mitigates lattice distortions during the first cycle. Because of these multifunctional roles, our new additive is shown to significantly improve capacity retention and perform better than previously reported organosilicon additives. These results establish (MetBu2Si)2CO as a sacrificial, self-limiting additive that leads to the formation of an interphase ensuring long-term cathode stabilization, thus offering a molecular-level strategy to enable durable high-voltage lithium-ion battery operation.

Zinc-bromine batteries (ZBBs) are promising candidates for large-scale energy storage due to their low cost, inherent safety, and high theoretical energy density. However, conventional flow-based ZBBs suffer from low system-level energy density and operational complexity. Recent interest has shifted toward flowless ZBBs (FL-ZBBs) configuration, yet these face critical challenges associated with uncontrolled diffusion and self-discharge (SD) of bromine species at the cathode. One of the holy grails in addressing these challenges is the use of quaternary ammonium salts (NR4+), which interact with bromine species to inhibit their diffusion. In this work, we demonstrate the first ever reported utilization of phosphonium-based bromine-complexing agents (BCAs) in FL-ZBBs. We do so by impregnation of the BCAs into porous carbon cathodes, particularly tetrabutylphosphonium bromide (TBP), which outperforms traditional ammonium-based analogs in FL-ZBBs. TBP enables high Coulombic efficiency (>98.5%, 1 A g(-)& sup1;) for 145 mAh g(-)& sup1;, reduces the SD phenomenon, and achieves long-term cycling stability of over 500 cycles with >97% CE (1.5 A g(-)& sup1;, 145 mAh g(-)& sup1;), even under low electrolyte concentrations (0.5 M ZnBr2). The enhanced performance is attributed to faster 2Br(-)/Br-2 redox kinetics, as demonstrated by cyclic voltammetry, and suggesting more favorable polybromide center dot center dot center dot PR4+ interactions, highlighting phosphonium salts as attractive BCA compounds for high-performance FL-ZBBs.

Sodium-ion batteries are progressively scrutinized for their economic viability and natural abundancy of resources. However, their practical implications are hampered by their limited energy density, primarily stemming from cationic redox reactions in transition-metal based cathodes. Achieving higher energy density via anionic redox activation is one of the promising approach but often compromises structural integrity due to lattice oxygen loss and transition metal migration. In this work, we present a strategy of covalency modulation through low-level Ru4+ doping in a Na-deficient, Co-free high-entropy (HE) layered cathode. By completely substituting Mn4+ with Ru4+ in HE cathode model, we enhance TM-O bond covalency and stabilize the oxygen framework. This effectively balances the trade-off between high capacity and structural stability, enabling reversible anionic redox activity while suppressing irreversible spinel formation and lattice strain. The Ru4+/Ru5+ couple improves voltage stability and delivers a high capacity of 146 mAh g(-1) (2-4.3 V, C/15), while Raman and OEMS studies confirm minimized surface degradation and oxygen release. Our findings demonstrate that the approach of entropy stabilization combined with targeted covalency tuning can supplemented the cathodes with both enhanced performance and longevity, offering a promising design pathway for next-generation sodium-ion batteries.

In the quest for advanced energy storage solutions, the stability and performance of electrolyte materials are of paramount importance. In particular, the redox potentials of electrolytes are of great interest, as these values dictate the electrochemical window that can be applied during battery cycling. Although redox trends can be estimated from computed frontier orbital energies and ionization potentials (IPs) and electron affinities (EAs), accurately representing long-range electrostatics is challenging. While solution-phase embedding schemes (e.g., continuum solvation, cluster-continuum, and polarizable/frozen-density embedding) are well established, their direct application and validation in electrolyte systems remain limited. In the current study, we adopt an integrated approach, combining classical molecular dynamics (MD) simulations and quantum mechanics-molecular mechanics (QM/MM) calculations to estimate the electrochemical stability of electrolytes. MD simulations of the electrolytes are first used to generate representative solution configuration ensembles, which are then subjected to QM/MM calculations to determine the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and the vertical IP and EA. To account for long-range electrostatics and configurational sampling, we consider increasingly larger solvation shells surrounding electrolyte molecules and perform ensemble averaging. Using this framework, we specifically study two widely used electrolytes for lithium- and sodium-ion batteries and investigate the effect of anion additives. The computed results are compared with experimental results from linear sweep voltammetry. We conclude that it is important to include several solvation shells to accurately compute the frontier orbitals of electrolyte molecules and to average the orbitals over configuration ensembles. The current approach for the first time computes the oxidative and reductive stability trends of electrolyte species while capturing the long-range effects and configuration ensembles of the environment. We also observe that, while vertical IP and EA values strongly correlate with HOMO and LUMO energies, structural relaxation of oxidized and reduced species weakens this correlation─particularly for organic carbonates upon reduction─highlighting the limitations of the simple HOMO-LUMO picture and the need to account for geometric relaxation in realistic redox predictions.

High-entropy (HE) materials comprise a family of emerging solid-state materials, where multiple elements can occupy the same lattice positions and therefore enhance the configurational entropy. HE oxides (HEOs) can mitigate challenges facing layered cathode materials, such as capacity fading, and facilitate long-term cyclability. However, the mechanism behind the effect of HE on electrochemical properties is still poorly understood. In the current work, we employed classical force field and first-principles density functional theory (DFT) calculations to gain atomistic-level understanding of the thermodynamic and electrochemical features of a family of recently developed high-entropy oxyfluoride (HEO-F) cathode materials with the general formula Na x Li1-x MO1.9F0.1 (M is an element of Ni, Fe, Mn, Ti, Mg; x = 1.0, 0.9, 0.8). We used Monte Carlo simulated annealing (MCSA) in conjunction with classical force fields to determine the most favorable atomic arrangement within these high-entropy oxyfluorides. Subsequently, we conducted DFT calculations at different sodium concentrations during charging, analyzing the oxidation states, Bader charges, and partial density of states of the transition metal (TM) atoms, to elucidate their participation in the redox processes. Crystal orbital Hamilton population (COHP) calculations were performed to assess the strength of the metal-oxygen bonds, which are crucial for the cathode stability. Furthermore, we investigated the potential occurrence of antisite defects, involving cation exchange between Li and TM atoms. Analyses of all three compositions of Na x Li1-x MO1.9F0.1 (x = 1.0, 0.9, 0.8) suggest that the Na0.9 system exhibits superior electrochemical properties, in agreement with experiments. We identified key factors that can contribute to this superior performance, including (1) low crystal lattice variation during cycling, (2) enhanced electronic conductivity, (3) optimal charge balancing among transition metal atoms at high desodiation, (4) strong metal-oxygen bonding, and (5) limited occurrence of energetically unfavorable antisite defects.

An anionic-additive electrolyte system is introduced by incorporating Lithium tetrafluoroborate (LiBF4) into a conventional base electrolyte for high-voltage LiNi0.Mn-5(1).O-5(4) (LNMO) cathodes in lithium-metal batteries. At high voltages, the sacrificial oxidation of LiBF4 mitigates electrolyte degradation and forms a robust cathode electrolyte interface (CEI) enriched with boron and fluorine-based components, which protects against active material corrosion. Density Functional Theory (DFT) studies reveal that BF4- is more readily oxidized, while MD simulations validate the CEI's inorganic composition. Initial cycling with a specialized charge-discharge protocol ensures optimal use of the additive, resulting in a uniform, thin (4-6 nm) CEI on the LNMO cathode. The CEI formed in anionic-additive electrolyte system effectively suppresses transition metal dissolution and surface degradation, enhancing long-term cycling performance. The LiBF4-enhanced electrolyte also lowers overpotential and promotes more uniform Li deposition compared to the base electrolyte. At a 1 C-rate, the LNMO cathode with a Li metal anode and optimized electrolyte achieves a discharge capacity of 115 mA h g(-)(1) and an energy density of 540 Wh kg(-)(1) over 500 cycles. These findings underscore LiBF4's dual role in protecting LNMO cathodes and Li metal anodes, highlighting the critical role of additives in CEI development for advanced lithium-metal batteries.

The introduction of the water-in-salt (WIS) electrolytes concept to prevent water splitting and widen the electrochemical stability window, has spurred extensive research efforts toward development of improved aqueous batteries. The successful implementation of these electrolyte solutions in many electrochemical systems shifts the focus from diluted to WIS electrolyte solutions. Considering the high costs and the tendency of these nearly saturated solutions to crystallize, this trend can be carefully re-evaluated. Herein we show that the stability of organic electrodes comprising the active material perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), is strongly influenced by the solvation character of the anions rather than the concentration of the electrolyte solution. Even though the charging process of PTCDA involves solely insertion of cations (i.e., principal counter-ions), surprisingly, the dominant factor influencing its electrochemical performance, including long-term electrode stability, is the type of the co-ions (i.e., electrolytic anions). Using systematic electrochemical analysis combined with theoretical simulations, we show that the selection of kosmotropic anions results in fast fading of the PTCDA anodes, while a selection of chaotropic anions leads to excellent stability, even at electrolytes concentrations as low as 0.2 M. These findings provide a new conceptual approach for designing advanced electrolyte solutions for aqueous batteries.

Energetic and structural stability of thirteen novel ternary transition metal tri-chalcogenide layers, claimed to be promising catalysts for hydrogen evolution reaction (HER), are studied. Detailed analyses of electronic structure, and mechanical and phonon properties establish that ten out of the thirteen materials are stable. Further analyses establish that these are chemically in the same class as the known layered ternary transition metal tri-chalcogenide materials. These lead us to claim that it should be possible to synthesize these materials experimentally, thus enlarging the list of candidate materials that can replace platinum as HER catalysts.

Nonaqueous rechargeable Li-O2 batteries are recognized as possible alternatives to the currently established Li-ion battery technology for next-generation traction by virtue of their high specific energy. However, the technology is still far from commercial realization mainly due to the performance-limiting reactions at the cathode. The insulating discharge product, Li2O2, can passivate the cathode leading to issues such as low specific capacity and early cell death. Herein, the -OH functionalities at the cathode, incorporated by polysaccharide addition, are shown to enhance the discharge capacity and cyclability. The -OH functional group (high pKa) at the cathode helps to stabilize the intermediate, LiO2, via an energetically favorable pathway and delays the precipitation to Li2O2, without any parasitic reaction, unlike the other reported low pKa additives. The role of the functionalities is studied using various experimental techniques and first principles density functional theory based studies. This approach provides a rational design route for the cathodes that provide high capacities for the emergent Li-O2 batteries.

A universal activity descriptor for catalytic alkaline hydrogen evolution reaction (HER) was unavailable, though metal-hydrogen binding energy can be considered as a good such descriptor in acidic medium. Herein, with the help of experimental and first principles density functional theory (DFT) based studies, we have shown that structural changes in the water coordination in electrolytes having high alkalinity can be a possible reason for the reduced catalytic activity of platinum (Pt) in high pH. Studies with polycrystalline Pt electrodes indicate that electrocatalytic HER activity reduces in terms of high overpotential required, high Tafel slope, and high charge transfer resistances in concentrated aqueous alkaline electrolytes (say 6M KOH) in comparison to that in low alkaline electrolytes (say 0.1M KOH), irrespective of the counter cations (Na+, K+ or Rb+) present. The changes in the water structure of bulk electrolytes with concentration are established using Raman, infrared, and 1H NMR based spectroscopic analyses. The changes in the interfacial water structure are also studied using in situ Raman scattering experiments where the changes in the coordination of water from tetrahedral to trihedral to free water are observed as the potential goes more cathodic towards HER. DFT based studies show enhanced water dissociation energy required for tetrahedrally coordinated water followed by trihedral, and then free water having the least dissociation energy for the Volmer process. But the water structure seems to be unaffected in anodic potentials. Hence the study paves new ways in studying the HER process in terms of the water structure near the electrode-electrolyte interface.

Tweaking the electrolyte of the anode compartment of zinc-air battery (ZAB) system is shown to be extending the charge-discharge cyclability of the cell. An alkaline zinc (Zn)-air cell working for ∼32 h (192 cycles) without failure is extended to >55 h (>330 cycles) by modifying the anode compartment with a mixture electrolyte of KOH and LiOH. The cell containing the mixture electrolyte has a low overpotential for charging along with high discharge capacity. The role of Li+ ions in tuning the electrode morphology and electrodics is studied both theoretically and experimentally. The synergistic effect of Li+ and K+ ions in the electrolyte on improved ZAB performance is proven. This study can pave new ways for the commercial implementation of ZAB, where it has already proven its potential in low-cost, high energy density, and mobility applications.

Electronic structure calculations based on density functional theory are used to identify the catalytically active sites for the hydrogen evolution reaction on single layers of the two transition metal tri-chalcogenide compounds CoPS3 and NiPS3. Some of the under-coordinated P and S atoms at the edges are found to act as the active sites, the details of which depend on the coverage of H on the electrode. Overpotentials along the two possible pathways for HER are also estimated for the two materials. These findings not only resolve an apparent discrepancy between published experimental results and our earlier calculations, but also provide insights which can be used to enhance catalytic efficiency of these materials further.

Electronic structure and catalytic activity in hydrogen evolution reactions (HER) of two ternary tri-chalcogenide nano-ribbons, MnPSe3 and FePSe3, have been investigated using first-principles electronic structure calculations. Specific edge sites have been identified as the catalytic centers in both these materials. HER catalytic activity has been predicted through determination of the hydrogen adsorption free energy following Nørskov's approach. This has been done both with and without considering effects of the aqueous solvent. Hydrogen coverage dependency of the catalytic activity have also been studied. Identification of the catalytically active edge sites on these materials bridges experimental observations and theoretical predictions on these materials.

Recent experiments showed that some layered ternary transition metal trichalcogenide compounds are efficient catalysts for the hydrogen evolution reaction (HER). Motivated by these, we have combinatorially designed and computationally screened, through an efficient, automated approach based on density functional theory, single layers of such compounds, including those not reported in widely used crystal structure database like the International Crystal Structure Database (ICSD), for their efficiency as HER catalysts. On the basis of our theoretical prediction of overpotentials determined from the reaction coordinate mapping corresponding to the HER mechanism, 13 of these compounds are found to be promising catalysts, out of which three are suggested to be as efficient as platinum, the best known HER catalyst to date.

The zinc-air battery (ZAB) is an emerging rechargeable energy storage system having high energy density (1084 Wh/kg) with safe operation and low operation cost (similar to$10 kW/h). Development of a durable and efficient bifunctional catalyst is the bottleneck of rechargeable ZAB technology, and here we demonstrate a hybrid catalyst system having cobalt (Co) nanoparticles dispersed graphitic spheres as an efficient catalyst at the air electrode-performing better than the benchmarked ones while constructing the ZAB cells. Co nanoparticles dispersed nitrogendoped graphitic nanospheres (Co@NGC-NSs) were developed using a unique synthesis strategy, and it showed excellent bifunctional catalytic activity toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline medium. The potential difference calculated with Co@NGC-NSs, considering the potential for the current density of 10 mAcm(-2) for OER and current density corresponding to the half wave potential for ORR, is found to be (0.78 V) lower than that of Pt/C and IrO2 (0.87 V) system. The zinc-air cell constructed using Co@NGC-NSs shows an open circuit voltage of 1.36 V having a maximum power density of similar to 52 mW cm(-2) and an energy density of 876 Wh/kg, and these values are on par with the Pt/C system while much better in terms of long-term stable performance where Pt/C is found to be failing. A detailed comparison with the reported performance of other catalyst-based ZABs indicates that the Co@NGC-NSs-based ZABs has high potential as a practically viable system, where the catalyst development is also found to be simple and nonexpensive in nature.

Details of the formation and dissociation of the first layer of Li2O2 on the α-MnO2(100) surface as the cathode in Li-air batteries have been studied using first principles density functional theory. The bias dependence of the electrochemical steps of charge (Li2O2 dissociation) and discharge (Li2O2 formation) via two different mechanisms has been studied. Discharge potential is found to be 2.94 V for the mechanism in which O2 adsorption is followed by lithiation. Charging potential for the reverse process is 3.37 V, giving an overpotential of 0.43 V, which is much lower than that on carbon electrodes. This is also in good agreement with experiments on α-MnO2 cathodes. In Li2O2 formation via the disproportionation of two LiO2 adsorbates, a maximum discharge potential of 2.61 V and a minimum charging potential of 3.48 V are obtained. The minimum energy pathway in this mechanism has a moderate kinetic barrier of 0.57 eV. Charging potentials of 3.37 V and 3.48 V imply that the typical charging potentials applied in the experiments (∼3.8 V) will dissociate the entire Li2O2 layer. These findings explain why α-MnO2 performs so well as a catalyst in Li-air battery cathodes, and suggest that a larger area of α-MnO2(100) can help reduce capacity loss.

Structural, electronic and magnetic properties of α-MnO2 subjected to pressure are studied using first principles electronic structure calculations. α-MnO2 is found to transform to the δ-MnO2 polymorph at ∼66 GPa of hydrostatic pressure. This comes as an interesting addition to the list of proposed transitions from non-layered to layered structures at high pressure. Unlike transition metal mono-oxides, α-MnO2 does not undergo any magnetic collapse up to this pressure. The pristine δ-MnO2 formed this way does not have intercalated ions or molecules, unlike δ-MnO2 synthesized by thermal treatment of KMnO4, but is found to be dynamically stable. This suggests that intercalation is not essential for its stability.

Structural, electronic and magnetic properties of alpha-MnO2 subjected to pressure are studied using first principles electronic structure calculations. alpha-MnO2 is found to transform to the delta-MnO2 polymorph at similar to 66 GPa of hydrostatic pressure. This comes as an interesting addition to the list of proposed transitions from non-layered to layered structures at high pressure. Unlike transition metal mono-oxides, alpha-MnO2 does not undergo any magnetic collapse up to this pressure. The pristine delta-MnO2 formed this way does not have intercalated ions or molecules, unlike delta-MnO2 synthesized by thermal treatment of KMnO4, but is found to be dynamically stable. This suggests that intercalation is not essential for its stability.