Migration Energy Barriers Research Articles

Investigation of the effect of off-stoichiometric composition on oxygen transport in layered perovskite materials for SOFC cathode

Layered perovskite materials are of significant interest for potential use as cathodes in solid oxide fuel cells. This study employs deep-learning-aided molecular dynamics simulations to investigate the impact of off-stoichiometric composition in praseodymium barium cobalt oxide and samarium barium cobalt oxide on O-ion transport properties. It is observed that increasing the deficiency of lanthanide-site atoms while suppressing the formation of O vacancies enhances O-ion mobility. This finding suggests adjusting synthetic conditions to achieve this state by controlling the design composition and heating atmosphere. The underlying mechanisms for the simulation results are explored, including the migration energy barrier of O ions, Co’s oxidation state change, and alterations in crystal structure, which indicate that structural changes and secondary phase formation are closely linked to O-ion mobility. Ba and Co infiltrate vacant lanthanide sites in the crystals under conditions of high lanthanide site deficiency and low O vacancy concentrations, promoting the formation of secondary phases composed of Ba, Co, and O, thereby creating favorable conditions for O-ion migration.

Effect of Al related chemical short-range order on the irradiation resistance of Al0.5CoCrFeNi multi-principal element alloy: A molecular dynamics simulation

Multi-principal element alloys (MPEAs) have received much attention for future nuclear materials due to their exceptional radiation resistance. This work investigated the effect of Al related chemical short-range ordered (CSRO) which caused by its large atomic size in face-centered cubic (FCC) Al0.5CoCrFeNi alloy on its irradiation damage behavior through mixed molecular dynamics and Monte Carlo simulations. The calculation results indicate that the CSRO structure effectively suppresses the generation of point defects during irradiation in Al0.5CoCrFeNi alloy, and this inhibitory effect increases with increasing irradiation energy. The enhanced radiation resistance of CSRO alloy is attributed to the high vacancy formation energy, interstitial atom formation energy, and vacancy migration energy barrier of Al. Moreover, the Al atoms in CSRO alloy can also act as defect barriers, preventing the migration of vacancy defects; The formation energy of interstitial atoms in the CSRO alloy exhibits a strong element dependence, and there is a significant difference in the formation energy of interstitial atoms between different points, which strengthens the hysteresis diffusion effect of MPEAs and further enhances the radiation resistance of MPEAs.

High-Humidity-Tolerant Chloride Solid-State Electrolyte for All-Solid-State Lithium Batteries.

Halide solid-state electrolytes (SSEs) hold promise for the commercialization of all-solid-state lithium batteries (ASSLBs); however, the currently cost-effective zirconium-based chloride SSEs suffer from hygroscopic irreversibility, low ionic conductivity, and inadequate thermal stability. Herein, a novel indium-doped zirconium-based chloride is fabricated to satisfy the abovementioned requirements, achieving outstanding-performance ASSLBs at room temperature. Compared to the conventional Li2ZrCl6 and Li3InCl6 SSEs, the hc-Li2+xZr1-xInxCl6 (0.3 ≤ x ≤ 1) possesses higher ionic conductivity (up to 1.4 mS cm-1), and thermal stability (350°C). At the same time, the hc-Li2.8Zr0.2In0.8Cl6 also shows obvious hygroscopic reversibility, where its recovery rate of the ionic conductivity is up to 82.5% after 24-h exposure in the 5% relative humidity followed by heat treatment. Theoretical calculation and experimental results reveal that those advantages are derived from the lattice expansion and the formation of Li3InCl6 ·2H2O hydrates, which can effectively reduce the migration energy barrier of Li ions and offer reversible hydration/dehydration pathway. Finally, an ASSLB, assembled with reheated-Li2.8Zr0.2In0.8Cl6 after humidity exposure, single-crystal LiNi0.8Mn0.1Co0.1O2 and Li-In alloy, exhibits capacity retention of 71% after 500 cycles under 1 C at 25°C. This novel high-humidity-tolerant chloride electrolyte is expected to greatly carry forward the ASSLBs industrialization.

Na2.5Cr0.5Zr0.5Cl6: A New Halide-Based Fast Sodium-Ion Conductor.

All-solid-state batteries employing solid electrolytes (SEs) have received widespread attention due to their high safety. Recently, lithium halides are intensively investigated as promising SEs while their sodium counterparts are less studied. Herein, a new sodium-ion conductor with a chemical formula of Na2.5Cr0.5Zr0.5Cl6 is reported, which exhibits high room temperature ionic conductivity of 0.1 mScm-1 with low migration energy barrier of ≈0.41eV. Na2.5Cr0.5Zr0.5Cl6 has a Fm-3m structure with 41.67mol.% of cationic vacancies owing to the occupation of Cr (8.33mol.%) and Zr (8.33mol.%) ions at Na sites. Supercell calculations show that the lowest columbic energy configuration has Cr/Zr/V (where V is the vacancy) clusters in the structure. Nonetheless, the clusters have mixed effects on the sodium ion conduction pathway, based on the Bond Valence Energy Landscape calculation. A global 3D Na-ion transport percolation network can be revealed in the lowest energy supercell. Effective pathways are connected through the NaCl6 and VCl6 nodes. Besides, Raman spectroscopy and 23Na solid-state nuclear magnetic resonance spectroscopy further prove the tunable structure of the SEs with different Cr to Zr ratios. The optimization between the concentration of Na+ and vacancies is crucial to create an improved network of Na+ diffusion channels.

Entropy Tuning Stabilizing P2‐Type Layered Cathodes for Sodium‐Ion Batteries

AbstractThe P2‐type layered transition metal oxide cathodes confront formidable challenges, including irreversible deleterious phase transitions, transition metals migration, and sluggish Na+ diffusion kinetics, which hamper their rapid commercial application in sodium ion batteries (SIB). In this work, an entropy tuning with dual‐site substitution strategy is proposed to address the aforementioned issues. In the tailored [Na0.67Zn0.05]Ni0.22Cu0.06Mn0.66Ti0.01O2 (NZNCMTO) cathodes, the strategic incorporation of Zn ions serves to occupy Na sites, intentionally disrupting the Na/vacancy ordering and establishing a reinforcing “pillar” effect within the layered framework. Furthermore, the substitution of Cu and Ti for Ni and Mn bolsters covalent bonding with the lattice oxygen, thereby impeding the migration of the transition metal ions and leading to a near‐zero strain structural evolution during charge and discharge process. Density functional theory calculations confirmed that entropy‐tuned NZNCMTO substantially lowered the migration energy barrier for Na+ ions diffusion and improved electronic conductivity. Consequently, the NZNCMTO cathode exhibits an impressive high practical capacity of 91.54 mAh g−1 at a high discharge rate of 10 C, along with outstanding cycling stability, maintaining near 100% capacity retention over 500 cycles at a current density of 10 C. This work presents an innovative blueprint for designing high‐performance sodium‐ion battery cathode materials.

Zinc ion modulation of hydrated vanadium pentoxide for high-performance aqueous zinc ion batteries

The structure of V2O5 as a cathode material is prone to collapse during repeated embedding/de-embedding of Zn2+, and the instability of the material limits its application. Introducing metal ions into the V2O5 layer provides larger ion channels, improves cycling kinetics, and acts as a pillar to enhance the structure stability during the charge/discharge process. In this study, Zn0·2V2O5·0.51H2O (ZVOH) is prepared by the hydrothermal method by embedding both Zn2+ and structural water molecules in the V2O5 interlayer. ZVOH is used as the cathode in zinc-ion batteries (ZIBs) with high power and energy densities (∼6779.3 W kg−1 and 289.6 Wh kg−1) and outstanding cycling stability. Furthermore, the valence changes of vanadium in ZVOH during charging and discharging as well as the morphological changes on the surface of the electrode material are investigated by ex-situ methods. The binding energy of Zn2+ at the sites within ZVOH and the migration energy barrier for Zn2+ migration on the ZVOH surface are also investigated by density functional theory.

Li3V2(PO4)3 particles embedded in N and S Co-doped porous carbon cathode for high performance lithium storage：An experimental and DFT study

Li3V2(PO4)3 (LVP)-coated with N and S co-doped carbon (NSC) is investigated by DFT calculation, suggesting that NSC significantly enhances electronic conductivity and lowers Li+ migration energy barrier in comparison to...

Realization of Mg2+ intercalation in a thermodynamically stable layer-structured oxide.

Magnesium batteries have emerged as one of the considerable choices for next-generation batteries. Oxide compounds have attracted great attention as cathodes for magnesium batteries because of their high output voltages and ease of synthesis. However, a majority of the reported results are based on metastable nanoscale oxide materials. This study puts forward a thermodynamically stable layer-structured oxide K0.5MnO2 with an enlarged lattice spacing as a model cathode material employing optimized electrolytes, enabling Mg2+ intercalation into the K0.5MnO2 framework in a real magnesium battery directly using Mg foil as the anode. First-principles calculations implied that the enlarged layer spacing could decrease the migration energy barrier of Mg2+ in the layered oxide. This work can pave the way to understanding the fundamental intercalation behavior of Mg2+ in magnesium batteries.

Diminishing the migration resistance of zinc ions by cation vacancy engineering in a spinel-framework

ZnMn2O4 with Zn vacancies has been constructed via alkaline etching, which shows lower diffusion energy barriers for Zn2+ than ZnMn2O4.

First-row transition metal carbide nanosheets as high-performance cathode materials for lithium-sulfur batteries.

Despite the prodigious potential of lithium-sulfur (Li-S) batteries as future rechargeable electrochemical systems, their commercial implementation is hindered by several vital issues, including the shuttle effect and sluggish migration of lithium-polysulfides leading to rapid capacity fading. Here, we systematically investigate the potential of first-row two-dimensional transition metal carbides (TMCs) as sulfur cathodes for Li-S batteries. The adsorption strength of lithium-polysulfides on TMCs is induced by the amount of charge transfer from the former to the latter and the proposed periodic relationship between sulfur in Li2S and 3d-transition metals. Our findings show that the VC nanosheet possesses immense anchoring potential and exhibits a comparatively low migration energy barrier for lithium-ion and Li2S molecules. Additionally, we report ab initio molecular dynamics simulations for lithiated polysulfide species anchored on a TMC-based model with a liquid-electrolyte medium. The microscopic reaction mechanism, revealed by the evolution of the reaction voltage during lithiation, demonstrates that the dissolution of high-order lithium-polysulfides in the electrolytes can be prevented due to their robust interaction with TMC-based cathode materials. These appealing features suggest that TMCs present colossal performance improvements for anchoring lithium-polysulfides, stimulating the active design of sulfur cathodes for practical Li-S batteries.

Phase-engineering compact and flexible CsPbBr3 microcrystal films for robust X-ray detection.

All-inorganic CsPbBr3 perovskites have gained significant attention due to their potential in direct X-ray detection. The fabrication of stable, pinhole-free thick films remains challenging, hindering their integration in durable, large-area high-resolution devices. In this study, we propose a facile strategy using a non-conductive polymer to create a flexible, compact thick film under ambient conditions. Furthermore, we investigate the effect of introducing the 2D CsPb2Br5 phase into CsPbBr3 perovskite crystals on their photophysical properties and charge transport. Upon X-ray exposure, the devices consisting of the dual phase exhibit improved stability and more effective operation at higher voltages. Rietveld refinement shows that, due to the presence of the second phase, local distortions and Pb-vacancies are introduced within the CsPbBr3 lattice. This in turn presumably increases the ion migration energy barrier, resulting in a very low dark current and hence, enhanced stability. This feature might benefit local charge extraction and, ultimately, the X-ray image resolution. These findings also suggest that introducing a second phase in the perovskite structure can be advantageous for efficient photon-to-charge carrier conversion, as applied in medical imaging.

First-principles calculations of point defect migration mechanisms in InP

As an important second-generation semiconductor material, indium phosphide (InP) possesses excellent advantages such as a wide bandgap, high electron mobility, high photoelectric conversion efficiency, and strong radiation resistance. It is considered an excellent material for electronic devices in aerospace applications. However, point defects generated by space radiation particles in InP electronic devices can cause their electrical performance to degrade severely. In this study, first-principles calculations are employed to investigate the stable structures of point defects in InP and calculate the migration energy values of nearest-neighbor defects. Four stable structures of In vacancies and three stable structures of P vacancies are identified by constructing the stable structures of point defects in different charge states. The migration process of vacancy defects is studied, revealing that the migration energy of P vacancies is higher than that of In vacancies. Moreover, charged vacancy defects exhibit higher migration energy values than neutral vacancies. Regarding the migration process of interstitial defects, it is found that the migration energy of interstitial defects is smaller than that of vacancy defects. In the calculation of In interstitial migration process with different charge states, two different migration processes are found. Besides, during the migration calculations of P interstitial, a special intermediate state is discovered, resulting in multiple paths migrating to the nearest-neighbor position in the migration energy barrier diagram. The research results are helpful to understand the formation mechanism and migration behavior of defects in InP materials, and are important in designing and manufacturing InP devices with long-term stable operation in space environment.

Dopant-Enhanced harmonization of α-Fe2O3 oxygen migration and surface catalytic reactions during chemical looping reforming of methane

The rate-matching between oxygen migration and surface catalytic reaction of oxygen carrier (OC) is a critical determinant for the reaction selectivity of the chemical looping reforming (CLR) of methane. However, the theoretical mechanism behind this rate-matching relationship is still unclear. Herein, we propose to use density functional theory (DFT) combined with microkinetic simulations to establish a model integrating the methane oxidation reactions with oxygen migration kinetics on α-Fe2O3 oxygen carrier. Our calculated results reveal that the transition metals (TMs)-doping such as Co, Ni, and Cu after Fe element in the periodic table can accelerate the oxygen migration rate as it promotes the upshift of the O p-band center. Moreover, a suitable oxygen migration energy barrier of about 1.0 eV is helpful to enhance the harmonization of α-Fe2O3 oxygen migration and surface catalytic reactions. Based on this, Ni-doping in α-Fe2O3 is predicted to be able to enhance the oxygen migration rate to match the rate of first-step methane dissociation, thereby simultaneously improving the reaction rate and the selectivity in the CLR of methane to syngas. These results could help to understand the relationship between oxygen migration and surface catalytic reaction rates and pave the way for the rational design of metal oxide oxygen carriers.

S dopant-mediated hydrogen evolution reaction activity of CoSe2

CoSe2 has become one of the most appealing non-noble metal catalysts for hydrogen evolution reaction (HER) in the field of electrolysis water due to its abundant resources and good activity. Inversely, its slow kinetic behavior is still restrained, which plays a negative influence for high-efficiency HER. Herein, a certain of Ni or S was introduced into the (100) crystal facet of CoSe2 on the basis of density functional theory (DFT) calculations. Thermodynamic calculation results reveal that the HER activity for CoSe1S1 is relatively better than those of Ni0.375Co0.625Se2 and pristine CoSe2 when a certain of S atoms were introduced into CoSe2. More strikingly, the active sites of CoSe1S1 are reversed from cationic Co to anion S, which is close to the ideal value (0) of Gibbs free energy. Meanwhile, the kinetic performance of H adsorbed on the anionic S or Se site is optimal, and their migration energy barrier is lower in comparison with 1/2 of the cationic Co site. According to the electronic structure analysis, the conductivity of CoSe1S1 is prominent than other counterparts (such as Ni0.375Co0.625Se2 and CoSe2). This work indicates that CoSe1S1 exhibits an excellent catalytic performance for HER, and offers theoretical guidance in the aspect of experiments for designing high-efficient HER catalysts.

MoS2@CoS2 heterostructured tube-in-tube hollow nanofibers with enhanced reaction reversibility and kinetics for sodium-ion storage

Rational synergism in spatial nanostructures and heterogeneity are effective ways to enhance reaction reversibility and kinetics of materials for sodium-ion battery electrodes. Herein, we have designed MoS2@CoS2 heterostructured tube-in-tube hollow nanofibers via simple electrospinning, pyrolysis and sulfuration processes. The unique double-walled tubular structure resulted from a stepwise crystallization accompanied by pyrolysis volume shrinkage. It has appropriate void space and abundant MoS2@CoS2 heterointerfaces that can effectively avoid the volumetric change during the reaction process and accelerate the whole infiltration of the electrolyte. The formed MoS2/CoS2 heterojunction introduces a built-in electric field, which increases the adsorption energy and reduces the migration energy barrier of sodium ions. The synergies between distinctive hollow structures and heterogeneous compositional advantages lead to enhanced electrochemical performance for sodium storage with remarkable reversible capacity (858.3 mAh g–1 at 0.5 A g–1), high-rate performance (555.7 mAh g–1 at 5 A g–1), and superior long-term cycling stability (399.6 mAh g–1 after 1400 cycles at 8 A g–1). This rational spatial structures and heterogeneity synergetic strategy provide favorable inspiration for designing extraordinary performance electrode materials for sodium-ion batteries.

Electrochemically Induced Phase Transformation in Vanadium Oxide Boosts Zn-Ion Intercalation.

Vanadium oxides are excellent cathode materials with large storage capacities for aqueous zinc-ion batteries, but their further development has been hampered by their low electronic conductivity and slow Zn2+ diffusion. Here, an electrochemically induced phase transformation strategy is proposed to mitigate and overcome these barriers. In situ X-ray diffraction analysis confirms the complete transformation of tunnel-like structural V6O13 into layered V5O12·6H2O during the initial electrochemical charging process. Theoretical calculations reveal that the phase transformation is crucial to reducing the Zn2+ migration energy barrier and facilitating fast charge storage kinetics. The calculated band structures indicate that the bandgap of V5O12·6H2O (0.0006 eV) is lower than that of V6O13 (0.5010 eV), which enhanced the excitation of charge carriers to the conduction band, favoring electron transfer in redox reactions. As a result, the transformed V5O12·6H2O delivers a high capacity of 609 mA h g-1 at 0.1 A g-1, superior rate performance (300 mA h g-1 at 20 A g-1), fast-charging capability (<7 min charging for 465 mA h g-1), and excellent cycling stability with a reversible capacity of 346 mA h g-1 at 5 A g-1 after 5000 cycles.

Lithium Distribution and Site Disorder in Halide-Substituted Lithium Argyrodites: A Structural and Transport Study

Lithium argyrodite superionic conductor has recently gained significant attention as a potential solid electrolyte for all-solid-state batteries because of its high ionic conductivity and ease of processing. One promising aspect of these materials is the ability to introduce halide (Li6-xPS5-xY1+x, Y = Cl and Br ) into the crystal structure, which can greatly impact the lithium distribution over the wide range of accessible sites and structural site-disorder between the S2₋ and Y₋ anion on Wyckoff 4d site, strongly influences the ionic conductivity. However, the relationship between halide substitution, structural site-disorder, and lithium distribution is not fully understood. In this study, we investigate the effect of halide substitution on lithium argyrodite and engineer site-disorder by changing the synthesis protocol. We reveal the lithium substructure and ionic transport correlations using neutron diffraction, solid-state NMR, and electrochemical impedance spectroscopy, We find that higher ionic conductivity is correlated with a negative charge on the 4d site, as replacing the S2− with Br− leads to a lowered average charge on the 4d site and weaker interactions within the Li+ “cage”, promoting a migration pathway for Li+ ions across the Li+ cage. We also identify a new T4 Li+ site, which enables an alternative jump route (T5–T4–T5) with a lower migration energy barrier. The resulting expansion of Li+ cages and increased connections between cages leads to a maximum ionic conductivity of 8.55 mS cm-1 with higher site-disorder, an improvement of 11-fold compared to lower site-disorder. Overall, this work provides a deeper understanding of the structure-transport correlations in lithium argyrodite, specifically how site-disorder and halide substitution impact the lithium substructure and transport properties.

Enhancement of performance and kinetics of layered Li2MnO3 by Fe doping

Layered Li2MnO3 exhibits great potential as a high-capacity cathode used in lithium-ion batteries, but materials synthesized by traditional solid-phase methods exhibit poor activity and poor cycling stability. In this work, Li2MnO3 nanoparticles were synthesized by solid state method combined with high-energy ball milling, in which Fe was doped at transition metal sites to obtain a Li-rich cathode material (Li1.32Fe0.034Mn0.64O2). We systematically studied the effects of Fe doping and calcination temperature on the crystal structure and electrochemical properties and conducted kinetic studies using the galvanostatic intermittent titration technique (GITT), electrical impedance spectroscopy (EIS) and density functional theory (DFT) calculations. Our results demonstrate that the performance was significantly improved, its discharge capacity is about 235 mAh g−1 after 10 cycles compared 138 mAh g−1 of the pristine sample. The GITT and EIS results show that the Fe-doped sample had smaller charge transfer impedance, larger lithium-ion diffusion coefficient and lower internal polarization than the pristine. The activation energy results show the Fe-doped sample has larger activation energy at the late discharging period due to the anion redox reaction activation, indicting its O activation is more active than Li2MnO3. Moreover, the DOS results showed that the Fe-doped sample had a narrow band-gap, indicating good electrical conductivity. The CI-NEB results showed that the Fe-doped sample had a high transition metal ion migration energy barrier, indicating that its structure was stable. In conclusion, Fe doping is helpful to active the anion redox reaction in Li2MnO3 and improve its electrochemical performance as a low cost and high-capacity cathode materials.

V4C3 MXene: a Type-II Nodal Line Semimetal with Potential as High-Performing Anode Material for Mg-Ion Battery.

We have used density functional theory simulations to explore the topological characteristics of a new MXene-like material, V4C3, and its oxide counterpart, assessing their potential as anode materials for Mg-ion batteries. Our research reveals that V4C3 monolayer is a topological type-II nodal line semimetal, protected by time reversal and spatial inversion symmetries. This type-II nodal line is marked by unique drumhead-like edge states that appear either inside or outside the loop circle, contingent upon the edge ending. Intriguingly, even with an increase in metallicity due to oxygen functionalization, the topological features of V4C3 remain intact. Consequently, the monolayer V4C3 has a topologically enhanced electrical conductivity that amplifies further upon oxygen functionalization. During the charging phase, a remarkable storage concentration led to a peak specific capacity of 894.73 mAh g-1 for V4C3, which only decreases to 789.33 mAh g-1 for V4C3O2. When compared to V2C, V4C3 displays a significantly lower specific capacity loss due to functionalization, demonstrating its superior electrochemical properties. Additionally, V4C3 and V4C3O2 exhibit moderate average open-circuit voltages (0.54 V for V4C3 and 0.58 V for V4C3O2) and energy barriers for intercalation migration (ranging between 0.29-0.63 eV), which are desirable for anode materials. Thus, our simulation results support V4C3 potential as an efficient anode material for Mg-ion batteries.

First-principles study on the properties of Ta doped P2-Na2/3Fe1/3Mn2/3O2 for Na-ion batteries

P2-Na2/3Fe1/3Mn2/3O2 (NFM) is a layered transition material with abundant raw materials, high specific capacity, and excellent cycling stability, a potential cathode material for sodium-ion batteries. The considerable size and substantial mass of Na+ present notable challenges concerning unfavorable reaction kinetics and structural instability during the insertion and extraction processes. This presents a formidable obstacle for practical applications. Ta5+ is characterized by higher valence and more muscular bonding energy, and doping Ta in NFM leads to the formation of a stable crystal structure. In the present work, we use first-principles calculations within the DFT + U framework to investigate different concentrations of Ta-doped MFMs to overcome these drawbacks. The calculated results show that the introduction of Ta elements reduces the formation energy and enhances the structural stability. It also enhances the electronic conductivity (i.e., the band gap, Eg = 0) and lowers the ion mobility barrier. In addition, we also investigate the electronic structure, spin, and magnetic properties of doping controlled electrode materials to investigate the doping effect regulating migration energy barriers. This study suggests that Ta-doped NFMT is a good alternative due to higher performance compared to the pristine NFM.