Voltage Hysteresis Research Articles

Alleviating Voltage Hysteresis by Interconnecting Truncated Octahedral LiNi0.5Mn1.5O4 Cathode Particles Using Exfoliated Graphene

AbstractHigh‐voltage spinel LiNi0.5Mn1.5O4 (LNMO) has been highlighted as one of the most promising cathode materials for next‐generation Li‐ion batteries. However, its performance is known to have shortcomings, i. e., voltage hysteresis induced by the increasing impedance of LNMO during electrochemical cycling at high voltage operation. This paper demonstrates an innovative design of LNMO cathode materials to alleviate voltage hysteresis by combining unique characteristics of truncated octahedral LNMO with 2D exfoliated graphene (EG). The exposed (100) plane of truncated LNMO particles is known to have superior Li+ ion conduction. Meanwhile, the (111) plane is known to have excellent resistance to metal dissolution. Moreover, it was revealed that the presence of the EG framework as an interconnection aide could significantly improve the charge transfer process, helping to alleviate the voltage polarization. The sample with optimum LNMO‐EG composition shows a stable electrochemical performance with a capacity retention of 86.56 % after 300 cycles of charge‐discharge measurement at 1 C while exhibiting almost 3 times lower voltage hysteresis (0.233 mV/cycle) compared to the pristine LNMO (0.678 mV/cycle). This result demonstrates that combining the uniqueness of truncated LNMO and 2D EG can be a promising strategy to improve the electrochemical performance of LNMO cathode materials for next‐generation batteries.

Improved p-GaN/AlGaN/GaN HEMTs with magnetronsputtered AlN cap layer

In this paper, a low temperature sputtered AlN cap-layer p-GaN HEMT with high gate breakdown and improved reliability is realized. XPS test shows that the valence band offset of p-GaN and low-temperature magnetron sputtered AlN is 1.2 eV, which successfully suppresses the gate leakage current and greatly improves the gate reliability. Low capacitance–voltage hysteresis and small pulsed threshold voltage shift predict good AlN/p-GaN interface quality. The threshold voltage of the AlN/p-GaN HEMT is improved from 0.61 V to 0.82 V compared to the conventional p-GaN HEMT with tungsten Schottky gate (W/p-GaN HEMT), the DIBL decrease from 34.4 mV/V in W/p-GaN HEMT to 1.1 mV/V in AlN/p-GaN HEMT. The gate forward and reverse leakage is significantly suppressed, and the gate forward breakdown voltage is improved to 17 V. The gate operating range is improved from 7 V to 12 V, and the ID/IG under saturation state is improved from 104 to 107. In addition, a smaller on-resistance of 67.5 Ω·mm was obtained, which is 15.3 % lower than that of the W/p-GaN HEMT, minimizing on-state loss. The gate leakage mechanism of the AlN/p-GaN HEMT is mainly dominated by the PF emission in the medium gate voltage range. Based on this leakage mechanism, the maximum forward VG for a ten-year lifetime was extracted as 6.8 V at room temperature at a failure level of 63.2 % for the AlN/p-GaN HEMT, while this value for W/p-GaN HEMT is 5.4 V. In addition, the AlN cap layer attenuates the depletion region of metal/p-GaN by the gate Schottky metal, which keeps the GaN channel better depleted, thus keeping a higher off-state breakdown voltage. These results demonstrate the good potential of magnetron sputtering AlN as a low-cost, methodologically simple growth method for the commercial use of p-GaN HEMTs.

Accurate Evaluation of Threshold Voltage Hysteresis in SiC MOSFET Under Switching Stress

Accurate Evaluation of Threshold Voltage Hysteresis in SiC MOSFET Under Switching Stress

Synergetic bifunctional Cu-In alloy interface enables Ah-level Zn metal pouch cells

Rechargeable aqueous zinc-metal batteries, considered as the possible post-lithium-ion battery technology for large-scale energy storage, face severe challenges such as dendrite growth and hydrogen evolution side reaction (HER) on Zn negative electrode. Herein, a three-dimensional Cu-In alloy interface is developed through a facile potential co-replacement route to realize uniform Zn nucleation and HER anticatalytic effect simultaneously. Both theoretical calculations and experimental results demonstrate that this bifunctional Cu-In alloy interface inherits the merits of low Zn-nucleation overpotential and high HER overpotential from individual copper and indium constituents, respectively. Moreover, the dynamical self-reconstruction during cycling leads to an HER-anticatalytic and zincophilic gradient hierarchical structure, enabling highly reversible Zn chemistry with dendrite-free Zn (002) deposition and inhibited HER. Moreover, the improved interface stability featured by negligible pH fluctuations in the diffusion layer and suppressed by-product formation is evidenced by in-situ scanning probe technology, Raman spectroscopy, and electrochemical gas chromatography. Consequently, the lifespan of the CuIn@Zn symmetric cell is extended to more than one year with a voltage hysteresis of 6 mV. Importantly, the CuIn@Zn negative electrode is also successfully coupled with high-loading iodine positive electrode to fabricate Ah-level (1.1 Ah) laminated pouch cell, which exhibits a capacity retention of 67.9% after 1700 cycles.

MOF-Derived Nitrogen-Rich Hollow Nanocages as a Sulfur Carrier for High-Voltage Aluminum Sulfur Batteries.

Aluminum-sulfur batteries (ASBs) are emerging as promising energy storage systems due to their safety, low cost, and high theoretical capacity. However, it remains a challenge to overcome voltage hysteresis and short cycle life in the sulfur/Al2S3 conversion reaction, which hinders the development of ASBs. Here, we studied a high-voltage ASB system based on sulfur oxidation in an AlCl3/urea electrolyte. Nitrogen-doped hollow nanocages (HNCs) synthesized from MOF precursors were rationally designed as sulfur/carbon composite electrodes (S@HNC), and the impact of the nitrogen species on the electrochemical performance of sulfur electrodes was systematically investigated. The S@HNC-900 achieved efficient conversion at 1.9 V, delivering a stable capacity of 197.3 mA h g-1 and a Coulombic efficiency of 93.28% after 100 cycles. Furthermore, the S@HNC-900 electrode exhibited exceptional rate capacity and 800th long-term cycling stability, retaining a capacity of 87.1 mA h g-1 at 500 mA g-1. Ex situ XPS and XRD characterizations elucidated the redox mechanism, revealing a four-electron transfer process (S/AlSCl7) at the S@HNC-900 electrode. Density functional theory calculations demonstrated that pyridinic nitrogen-enriched HNC-900 significantly enhanced the sulfur conversion reaction and facilitated the adsorption of sulfur intermediates (SCl3+) on the carbon interface. This work provides critical insights into the high-voltage sulfur redox mechanism and establishes a foundation for the rational design of carbon-based electrocatalysts for the enhancement of ASB performance.

Control of ferroelectricity in Ta-doped HfO2 and its non-zero-crossing current–voltage hysteresis behavior

Hafnium oxide (HfO2)-based ferroelectrics are being explored as potential candidates for ferroelectric memory devices due to their highly compatibility with complementary metal-oxide-semiconductor (CMOS) technology. Enhancing the remanent polarization and investigating the underlying mechanism are crucial tasks. In the present study, tantalum (Ta) was introduced as a dopant to induce ferroelectric properties in HfO2, a large portion of orthorhombic phase was recognized in the as-grown Ta:HfO2 without further thermal treatment. The remanent polarization of Ta:HfO2 thin films can be optimized by adjusting the oxygen flow rates during the sputtering process. The influencing factors for enhanced ferroelectric performance include the control of Ta concentration, its valence state, and the presence of singly ionized oxygen vacancies, which are influenced by oxygen addition. Furthermore, the resistive switching behavior showing non-zero crossing current–voltage (I–V) hysteresis is associated with ferroelectricity and the presence of oxygen vacancies. A model has been proposed to explain the ferroelectric resistive switching with non-zero crossing I–V characteristics by considering the role of oxygen vacancies and polarization effects. This model suggests that the oxygen vacancies at the surface layer, along with ferroelectric polarization, play a crucial role in electron transport.

Challenges and Prospects of Low-Temperature Rechargeable Batteries: Electrolytes, Interfaces, and Electrodes.

Rechargeable batteries have been indispensable for various portable devices, electric vehicles, and energy storage stations. The operation of rechargeable batteries at low temperatures has been challenging due to increasing electrolyte viscosity and rising electrode resistance, which lead to sluggish ion transfer and large voltage hysteresis. Advanced electrolyte design and feasible electrode engineering to achieve desirable performance at low temperatures are crucial for the practical application of rechargeable batteries. Herein, the failure mechanism of the batteries at low temperature is discussed in detail from atomic perspectives, and deep insights on the solvent-solvent, solvent-ion, and ion-ion interactions in the electrolytes at low temperatures are provided. The evolution of electrode interfaces is discussed in detail. The electrochemical reactions of the electrodes at low temperatures are elucidated, and the approaches to accelerate the internal ion diffusion kinetics of the electrodes are highlighted. This review aims to deepen the understanding of the working mechanism of low-temperature batteries at the atomic scale to shed light on the future development of low-temperature rechargeable batteries.

Probing Phase Formation and Structural Transformations in Sodium Extraction and Insertion of NaFe1-yMnyPO4 through First-Principles Calculations.

Manganese (Mn) substitution is a widely explored strategy aimed at sustainably enhancing the energy density of iron (Fe)-based electrode materials by taking advantage of the higher redox potential of the former. However, excessive Mn content can lead to detrimental effects, offsetting the expected improvements. In experimental studies, triphylite NaFe0.8Mn0.2PO4 has been identified as an optimal composition with enhanced electrochemical performance compared to that of its parent phase NaFePO4. Higher Mn contents result in a loss of capacity and increased voltage hysteresis. In this study, density functional theory (DFT) calculations were employed to investigate the phase stability upon desodiation of Mn-poor and -rich NaxFe1-yMnyPO4 compositions. Our findings reveal distinct stability behaviors in antagonistic systems NaxFe0.75Mn0.25PO4 and NaxFe0.25Mn0.75PO4, where the presence of Na-vacancies and charge orderings appear to influence phase stability. In addition, the number of intermediate phases throughout the desodiation process is identified as a crucial factor in buffering the volume changes. This work sheds light on the superior electrochemical performance of lightly Mn-substituted phases and unveils a key parameter for designing future electrode materials with improved performance.

Entropy-Stabilized Multication Fluorides as a Conversion-Type Cathode for Li-Ion Batteries-Impact of Element Selection.

Metal fluorides (e.g., FeF2 and FeF3) have received attention as conversion-type cathode materials for Li-ion batteries due to their higher theoretical capacity compared to that of common intercalation materials. However, their practical use has been hindered by low round-trip efficiency, voltage hysteresis, and capacity fading. Cation substitution has been proposed to address these challenges, and recent advancements in battery performance involve the introduction of entropy stabilization in an attempt to facilitate reversible conversion reactions by increasing configurational entropy. Building on this concept, high entropy fluorides with five cations were synthesized by using a simple mechanochemical route. In order to examine the impact of element selection, Co0.2Cu0.2Ni0.2Zn0.2Fe0.2F2 (HEF-Fe) was compared with Co0.2Cu0.2Ni0.2Zn0.2Mg0.2F2 (HEF-Mg), replacing electrochemically inactive Mg with Fe as an active participant in the conversion reaction. Combining electrochemical measurements with first-principles calculations, high-resolution electron microscopy, and synchrotron X-ray analysis, HEFs' battery performances and conversion reaction mechanisms were investigated in detail. The results highlighted that replacement of Mg with Fe was beneficial, with enhanced capacity, rate capability, and surface stability. In addition, it was found that HEF-Fe showed similar cycle stability without an electrochemically inactive element. These findings provide valuable insights for the design of high entropy multielement fluorides for improved Li-ion battery performance.

Electronic Confinement-Restrained Anti-Site Defects in Sodium-Rich Phosphates Toward Multi-Electron Transfer and High Energy Efficiency.

Sodium (Na) super-ionic conductor structured Na3MnTi(PO4)3 (NMTP) cathodes have garnered interest owing to their cost-effectiveness and high operating voltages. However, the voltage hysteresis phenomenon triggered by anti-site defects ( -ASD), namely, the occupation of Mn2+ in the Na2 vacancies in NMTP, leads to sluggish diffusion kinetics and low energy efficiency. This study employs an innovative electronic confinement-restrained strategy to achieve the regulation of -ASD. Partial replacement of titanium (Ti) with electron-rich vanadium (V) favors strong electronic interactions with Mn2+, restraining Mn2+ migration. The results suggest that this strategy can significantly increase the vacancy formation energy and migration energy barrier of manganese (Mn), thus inhibiting -ASD formation. As proof of this concept, an Na-rich Na3.5MnTi0.5V0.5(PO4)3 (NMTVP) material is designed, wherein the electronic interaction enhanced the redox activity and achieved more Na+ storage under high-voltage. The NMTVP cathode delivered a reversible specific capacity of up to 182.7 mAh g-1 and output an excellent specific energy of 513.8Wh kg-1, corresponding to ≈3.2 electron transfer processes, wherein the energy efficiency increased by 35.5% at 30C. Through the confinement effect of electron interactions, this strategy provides novel perspectives for the exploitation and breakthrough of high-energy-density cathode materials in Na-ion batteries.

A Comprehensive Study on the Parameters Affecting Magnesium Plating/Stripping Kinetics in Rechargeable Mg Batteries

AbstractMg metal anode‐based battery is a more sustainable, lower cost, and higher energy density alternative to Li‐ion. However, this battery chemistry also faces several challenges associated with the high charge density of Mg2+, including achieving high reversibility and low voltage hysteresis for Mg metal plating/stripping. While significant improvements are achieved in last decades, they involve rather complex electrolyte formulations and/or Mg salts difficult to produce, and the use of unpractical substrates such as platinum. Here, significant improvement in terms of Mg plating kinetics is achieved in electrolytes containing commercial magnesium bis(trifluoromethanesulfonyl)imide salt (Mg(TFSI)2) by using titanium substrate with similar crystal structure and lattice parameter as Mg leading to lower nucleation overpotential. Low salt concentration electrolyte and addition of dibutyl magnesium (Mg(butyl)2) also enable the formation of thinner interphase, richer in solvent based decomposition products, further improving Mg plating kinetics. This work highlights the complex role of Mg(butyl)2, often considered as a simple drying agent, and how it impacts ion solvation favoring the mobility of electroactive cationic species, paving the way toward better electrolyte design with improved cation transference number.

Direct ink writing of engineered MOF-based hybrid composite empowering dendrite free zinc ion battery anode

The relationship between morphology and electrochemical performance of zinc-ion battery (ZIB) anodes is crucial. Optimizing zinc-ion intercalation efficiency, suppressing dendrite formation, and mitigating shape changes are achievable through thoughtful anode architecture design. Herein, we have engineered a hybrid composite by coordinating a metal-organic framework with phenolic formaldehyde resin using a direct ink writing approach to rationally design a gridline-patterned 3DP-UiON-PHC@Zn. This anode in a symmetrical cell shows exceptional stability with a low voltage hysteresis of 15 mV at 0.1 mA cm−2 over 2375 h and 67 mV at 0.5 mA cm−2 over 4470 h. When paired with a 3DP-VOC@Al cathode in a full cell, it achieves a remarkable areal capacity of 85.1 mAh cm2 (94.8 %) and maintains a capacity retention of 122 mAh g−1 (88.6 %) over 900 cycles at 0.1 A g−1. It also offers a power density of 69.1 W kg−1 and an energy density of 34.6 Wh kg−1. Kinetic analysis reveals that the charge storage mechanism is primarily capacitive (94.7 %). This study concludes that DIW significantly improves anode performance by minimizing dendrite growth and improving electrochemical stability, while the 3D-printed hybrid composite ensures robust mechanical stability and a porous structure.

Multi-Component Lithiophilic Alloy Film Modified Cu Current Collector for Long-Life Lithium Metal Batteries by a Novel FCVA Co-Deposition System.

Surface modification of Cu current collectors (CCs) is proven to be an effective method for protecting lithium metal anodes. However, few studies have focused on the quality and efficiency of modification layers. Herein, a novel home-made filtered cathode vacuum arc (FCVA) co-deposition system with high modification efficiency, good repeatability and environmental friendliness is proposed to realize the wide range regulation of film composition, structure and performance. Through this system, ZnMgTiAl quaternary alloy films, which have good affinity with Li are successfully constructed on Cu CCs, and the fully enhanced electrochemical performances are achieved. Symmetrical cells constructed with modified CCs maintained a fairly low voltage hysteresis of only 13mV after 2100h at a current density of 1mA cm-2. In addition, the capacity retention rate is as high as 75.0% after 100 cycles in the full cells. The influence of alloy films on the dynamic evolution process of constructing stable artificial solid electrolyte interphase (SEI) layer is revealed by in situ infrared (IR) spectroscopy. This work provides a promising route for designing various feasible modification films for LMBs, and it displays better industrial application prospects than the traditional chemical methods owing to the remarkable controllability and scale-up capacity.

Strong Magnetic Exchange Interactions and Delocalized Mn-O States Enable High-Voltage Capacity in the Na-Ion Cathode P2-Na0.67[Mg0.28Mn0.72]O2.

The increased capacity offered by oxygen-redox active cathode materials for rechargeable lithium- and sodium-ion batteries (LIBs and NIBs, respectively) offers a pathway to the next generation of high-gravimetric-capacity cathodes for use in devices, transportation and on the grid. Many of these materials, however, are plagued with voltage fade, voltage hysteresis and O2 loss, the origins of which can be traced back to changes in their electronic and chemical structures on cycling. Developing a detailed understanding of these changes is critical to mitigating these cathodes' poor performance. In this work, we present an analysis of the redox mechanism of P2-Na0.67[Mg0.28Mn0.72]O2, a layered NIB cathode whose high capacity has previously been attributed to trapped O2 molecules. We examine a variety of charge compensation scenarios, calculate their corresponding densities of states and spectroscopic properties, and systematically compare the results to experimental data: 25Mg and 17O nuclear magnetic resonance (NMR) spectroscopy, operando X-band and ex situ high-frequency electron paramagnetic resonance (EPR), ex situ magnetometry, and O and Mn K-edge X-ray Absorption Spectroscopy (XAS) and X-ray Absorption Near Edge Spectroscopy (XANES). Via a process of elimination, we suggest that the mechanism for O redox in this material is dominated by a process that involves the formation of strongly antiferromagnetic, delocalized Mn-O states which form after Mg2+ migration at high voltages. Our results primarily rely on noninvasive techniques that are vital to understanding the electronic structure of metastable cycled cathode samples.

Electric Field Regulator Constructed by Magnetron Sputtering for Dendrite‐Free and Stable Zinc Metal Anode

AbstractRechargeable aqueous zinc‐ion batteries (AZIBs) are considered to be one of the most promising devices in the next generation of energy storage systems. However, the uncontrolled growth of Zn dendrites during electroplating leads to rapid battery failure, which hinders the wide application of AZIBs. In this work, an Fe metal interface (FMI) with electric field regulation is designed on the Zn metal anode using a magnetron sputtering technology. The FMI layer with nanosheet array not only uniforms the surface electric field, but also adjusts the surface Zn2+ ion distribution to inhibit 2D diffusion. The strong orientation relationships of the FMI layer enhance the reversibility of Zn plating/stripping, improving the structural stability of the interface layer. Consequently, FMI@Zn symmetric cell exhibits ultra‐stable lifespan for over 6000 h (Cumulative plated capacity, CPC = 15 Ah cm−2) with a low voltage hysteresis of 46.4 mV and high Coulombic efficiency of 99.8% at 5 mA cm−2. Even at the large current density of 40 mA cm−2, the CPC reaches 19.7 Ah cm−2. The proposed electric field regulation strategy reveals a promising prospect for designing highly stable Zn anode, which also applies to other metal anodes in energy storage systems.

Revealing Defect Passivation and Charge Extraction by Ultrafast Spectroscopy in Perovskite Solar Cells through a Multifunctional Lewis Base Additive Approach

Defect passivation inside the crystal lattice and the grain‐boundary (GB) surface of the perovskite films has become the most effective strategy to suppress the negative impact of the nonradiative recombination in perovskite solar cell. In this study, a unique approach to effectively passivate the defect states of MAPbI3 perovskite thin film using thionicotinamide (TNM) as a multifunctional Lewis base additive is demonstrated. TNM as an additive with three different types of Lewis base sites, i.e., pyridine, amino, and CS functional groups, is introduced to mitigate the trap states in the TNM‐modified perovskite films and thoroughly investigate the passivation defects. The nonbonded electron of the three different Lewis base sites can synergistically passivate the antisite lead (Pb) defects and improve the stability of the device. In addition, the NH2 group can form ionic bonds with negatively charged I– ions and inhibit ion migration caused by them. It is found that such passivation effect of TNM reduces the GB defects and improves the crystallinity significantly. As a result, a champion TNM‐modified device shows an improved power conversion efficiency of 19.26% from 16.86% along with enhanced open‐circuit voltage, fill factor, and negligible hysteresis.

LiF/ LixPOy/ LixPOyFz-based artificial interface on graphitic cathode for improving the cycle life of dual ion batteries

The emerging dual-ion batteries are a sustainable analog of conventional Lithium-ion batteries. It yields high voltage output and satisfying capacity, replacing transition metal-based cathodes with graphitic carbon. Despite the advantages, the systems suffer from inadequate cycling efficiencies and triggered electrolyte decomposition on cathode surface that cut short the cycle life. As a protective measure, the carbon cathode is coated using a LiF/LixPOy/LixPOyFz-based hybrid coating layer derived from the thermal decomposition of LiPF6 salt. The coated layer acts as an artificial interface that safeguards the surface from electrolyte attack and enhances cycling efficiencies. It forms a mechanochemically robust cathode-electrolyte interface that preserves the graphitic order and structural integrity of the electrode. As a result, the bulk of the coated material is not ruptured like in the uncoated pristine sample, thereby assisting in long-term cycling. The coated material retains 85 % capacity even after 1000 cycles with a 10 % improved coulombic efficiency and 130 mV reduced voltage hysteresis instead of losing 15 % capacity within 50 cycles with poor efficiency and elevated resistances in the pristine material. The strategy brings fruitful outcomes when applied in dual carbon cell and is believed to be equally effective in other dual-ion systems.

Reversing lithium dendrites via trigger-type carbonized ZIF-8 gradient for stable lithium metal anodes

Although metallic lithium is one of the most potential anode candidates for next-generation batteries, its applications are still restricted by several problems, especially the formation of lithium dendrites. However, insufficient emphasis has been placed on dealing with the incipient lithium dendrites. Herein, a three-dimensional insulating glass-fiber skeleton with gradient-distributed trigger-type carbonized ZIF-8 (GF-cZIF8) was developed. In this structure, plentiful conductive cZIF-8 on the collector/skeleton interface guided uniform lithium nucleation, while highly conductive and lithophilic cZIF-8 on the skeleton passivated and reversed lithium dendrites to a stable part of lithium anode when trigged by lithium dendrites. In addition, insulating glass fibers improved the homogeneity of Li ions. As a consequence, the GF-cZIF8/Cu collector exhibited a high and stable coulombic efficiency of 98 % after 280 cycles, and the GF-cZIF8-Li anode exhibited a low voltage hysteresis of 17 mV and a long cycling life up to 1100 h.

Review on layered oxide cathodes for sodium‐ion batteries: Degradation mechanisms, modification strategies, and applications

AbstractExploiting high‐capacity cathode materials with superior reliability is vital to advancing the commercialization of sodium‐ion batteries (SIBs). Layered oxides, known for their eco‐friendliness, adaptability, commercial viability, and significant recent advancements, are prominent cathode materials. However, electrochemical cycling over an extended period can trigger capacity fade, voltage hysteresis, structural instability, and adverse interface reactions which shorten the battery life and cause safety issues. Thus, it is essential to require an in‐depth understanding of degradation mechanisms of layered oxides. In this review, the crystal and electronic structures of layered oxides are revisited first, and a renewed understanding is also presented. Three critical degradation mechanisms are highlighted and deeply discussed for layered oxides, namely Jahn–Teller effect, phase transition, and surface decomposition, which are directly responsible for the inferior electrochemical performances. Furthermore, a comprehensive overview of recently reported modification strategies related to degradation mechanisms are proposed. Additionally, this review discusses challenges in practical application, primarily from a degradation mechanism standpoint. Finally, it outlines future research directions, offering perspectives to further develop superior layered cathode materials for SIBs, driving the industrialization of SIBs.

Strong Covalent Metal-Ligand Interaction Enables a Fast Kinetic and Structurally Stable Na-Ion Layered Cathode.

Anionic redox chemistry has attracted increasing attention for the improvement in the reversible capacity and energy density of cathode materials in Li/Na-ion batteries. However, adverse electrochemical behaviors, such as voltage hysteresis and sluggish kinetics resulting from weak metal-ligand interactions, commonly occur with anionic redox reactions. Currently, the mechanistic investigation driving these issues still remains foggy. Here, we chemically designed Na0.8Fe0.4Ti0.6S2 and Na0.8Fe0.4Ti0.6O2 as model cathodes to explore the covalency effects on metal-ligand interactions during anionic redox process. Na0.8Fe0.4Ti0.6S2 with strengthened covalent interaction of metal-ligand bonds exhibits smaller voltage hysteresis and faster kinetics than Na0.8Fe0.4Ti0.6O2 during (de)sodiation process. Theoretical calculations suggest that Fe is the dominant redox-active center in Na0.8Fe0.4Ti0.6S2, whereas the redox-active center moves from Fe to O with the removal of Na+ in Na0.8Fe0.4Ti0.6O2. We attribute the above different redox behaviors between Na0.8Fe0.4Ti0.6S2 and Na0.8Fe0.4Ti0.6O2 to the charge transfer kinetics from ligand to metal. Moreover, the structural stability of Na0.8Fe0.4Ti0.6S2 is enhanced by increasing the cation migration barriers through strong metal-ligand bonds during desodiation. These insights into the originality of metal-ligand interactions provide guidance for the design of high-capacity and structurally stable cathode materials for Li/Na-ion batteries.