Cathode Surface Research Articles

Erosion Pits Distribution Characteristics of Nanosecond Pulse Gas Spark Switches at Different Repetition Rates

Gas spark switches are widely used in the field of nanosecond pulses. Lifetime is one of the key parameters of a gas spark switch, which is closely related to the distribution of erosion pits A repetition rate nanosecond pulsed discharge experimental platform is set up to investigate the distribution characteristics of erosion pits on the electrodes of nanosecond pulsed gas spark switch under different repetition rates. The distribution of erosion pits on the electrodes at different repetition rates has been analyzed statistically through a metallographic microscope. The results indicate that the range of erosion pits on the surface of electrodes is linearly related to the repetition rate. As the switch repetition rate increases, the range of erosion pits expands. The range of erosion pits on the cathode surface is slightly larger than that on the anode. When the repetition frequency increases from 1 Hz to 100 Hz, the radius of the anode pit range increases from 7.27 mm to 9.2 mm, and the cathode pit range increases from 8 mm to 9.73 mm. The density of erosion pits is related to the normalized electric field intensity in power function. With the increase in repetition rate, the tendency for erosion pits to concentrate at the geometric center of the electrode weakens. This research is of significant importance for the design of long-life gas spark switches.

Effective ignition energy for capacitor short-circuit discharge in explosive environments

Capacitors short-circuit discharge in an explosive environment can ignite and detonate the surrounding explosive media, causing dangerous accidents. At low voltages, this kind of discharge constitutes a micro-nano discharge; because the discharge gaps here are of the order of only microns to nanometers, the discharge process, electrode energy consumption, explosive media ignition energy, and other energy relationships are unclear. To study the relationships between the capacitor storage energy and various kinds of dissipation energies under short-circuit discharge, a model comprising conical and spherical cylinder microbumps is proposed based on the cathode surface morphology obtained by three-dimensional profiling and scanning electron microscopy, respectively. Then, the second-order non-chi-squared differential equations were established based on the principle of energy conservation and heat balance to deduce the relationships between the cathode surface temperature and height of the microbump, conical angle, and spherical radius; further, the energy consumed by the anode surface is calculated based on the theory of heat transfer. Using heat conduction theory, the energy consumed by the microbumps on the cathode surface is calculated, and the energy consumed on the anode surface is deduced using the surface heat source as the loading heat source. The residual energy of the capacitor is calculated from the discharge time and voltages before and after discharge, and the effective energy of the gas is calculated using the law of conservation of energy. Finally, the discharge channel energy, electrode energy consumption, and end residual energy of the discharge capacitor are used to derive the effective ignition energy of the explosive gas. This research is of great significance for the design of intrinsically safe circuits with high power.

Efficient selenate removal from impaired waters with TiO2-assisted electrocatalysis

Aquatic selenium (Se) oxyanions have profound ecosystem and human health impacts, necessitating their conversion and immobilization into elemental Se(0) to mitigate the aquatic Se pollution. While thermodynamically favorable, this transformation encounters kinetic limitations, especially for selenate (SeO42−) or Se(VI). To lower the activation barrier, we investigated the electrocatalytic Se(VI) transformation using five affordable catalysts on graphite cathodes, including TiO2, underpotentially deposited Cu (UPD Cu), underpotentially deposited Cd (UPD Cd), Co, and CuFe. Among these five catalysts, we identified characteristic Se(VI) reduction peaks for TiO2 through cyclic voltammetry. Other catalysts removed less than 5% of 1-mM Se(VI) in 24-h chronoamperometry tests while leaching ppm-level metal cations in the treated water. In contrast, TiO2 as the electrocatalyst could remove more than 80% of 1-mM Se(VI) with negligible catalyst dissolution. Mechanistic investigations revealed a six-electron Se(VI)/Se(0) reduction pathway at -0.30 V (vs. Ag/AgCl), resulting in red Se(0) deposits on the TiO2-coated graphite cathode. Further potential decrease to more negative than -0.45 V led to Se(-II) formation, triggering cathodic Se(0) dissolution and surface regeneration. Electrochemical impedance spectroscopy indicated that Se(VI) reduction was optimal with a moderate TiO2 loading of 0.55 mg cm−2 and acidic environments (pH=1.0∼2.5), achieving an optimized removal of 88.7 ± 2.3% under -0.70 V and an energy input of 3.6 kWh kg−1 Se. These findings lay the foundation for efficient selenate removal from impaired waters. Future efforts should evaluate catalyst performance over time and refine electrode and reactor designs to improve efficiency.

Cathode cooling effects on the neutron production rate in the glow discharge type of fusion neutron source

Fusion reactions on the cathode surface of glow discharge deuterium–deuterium fusion neutron sources contribute significantly to the neutron production rate (NPR). While the NPR shows a linear relationship with current in the low current regime, a rise in cathode temperature in the high-current regime causes stagnation of the NPR. This tendency may be caused by high-temperature-induced desorption of deuterium on the cathode. This study aims to clarify the relationship between NPR and deuterium desorption. The present study utilized a water-cooling system to prevent deuterium desorption on the cathode. A stainless-steel 304 cathode and a diamond-like carbon (DLC)-coated cathode were tested. The cooling system kept the cathode temperature below 315 K throughout the experiment. In the case of the DLC-coated cathode, the water-cooling system improves the NPR in a high-current regime (30 mA or more in the present study). At 50 kV and 60 mA, the NPRs were 1.87 × 106 and 8.39 × 105 (n/s), with and without water cooling, respectively. Furthermore, without the cooling system, the NPR correlation with the cathode temperature indicates good agreement with the estimation model of deuterium desorption on the DLC-coated cathode. This study demonstrates that suppression of deuterium desorption in the cathode improves NPR, especially in the high-current regime.

An Electrochemical-Cycling-Induced Capacitive Component on the Surface of an Electrophoretic-Deposited Lithium Iron Phosphate Cathode

An Electrochemical-Cycling-Induced Capacitive Component on the Surface of an Electrophoretic-Deposited Lithium Iron Phosphate Cathode

Temperature-Responsive Formation Cycling Enabling LiF-Rich Cathode-Electrolyte Interphase.

Formation of LiF-rich cathode-electrolyte interphase is highly desirable for wide-temperature battery, but its application is hindered by the unwanted side reactions associated with conventional method of introducing fluorinated additives. Here, we developed an additive-free strategy to produce LiF-rich cathode electrolyte interphase (CEI) by low-temperature formation cycling. Using LiNi0.33Mn0.33Co0.33O2 as a model cathode, the atomic ratio of LiF in the CEI formed at -5 °C is about 17.7 %, enhanced by ~550 % compared to CEI formed at 25 °C (2.7 %). The underlying mechanism is uncovered by both experiments and theoretic simulation, indicating that the decomposition of LiPF6 to LiF is transformed into spontaneous and exothermic on positively charged cathode surface and lowering the temperature shift chemical equilibrium towards the formation of LiF-rich CEI. Superior to conventional fluorinated additives, this approach is free from unwanted side reactions, imparting batteries with both high-temperature (60 °C) cyclability and low-temperature rate performance (capacity enhanced by 100 % at 3 C at -20 °C). This low-temperature formation cycling to construct LiF-rich CEI is extended to various cathode systems, such as LiNi0.8Mn0.1Co0.1O2, LiCoO2, LiMn2O4, demonstrating the versatility and potential impact of our strategy in advancing the performance and stability of wide-temperature batteries and beyond.

Model of non-equilibrium near-cathode plasma layers for simulation of ignition of high-pressure arcs on cold refractory cathodes

The introduction of secondary ion-electron emission into an approximate model of non-equilibrium plasma layers on hot (thermionic) cathodes of high-pressure arc discharges allows extending the model to low cathode surface temperatures. Analysis of evaluation results shows that the extended model describes glow-like discharges on cold cathodes and thermionic arc discharges on hot cathodes, as it should. In the course of glow-to-arc transitions on cold cathodes, a transient regime occurs where a hot arc spot has just formed and a significant fraction of the current still flows to the cold surface outside the spot, so that the near-cathode voltage continues to be high. The power input in the near-cathode layer is very high in this regime, and so is the electron temperature in the near-cathode region. The mean free path for collisions between the atoms and the ions in these conditions exceeds the thickness of the layer where the ion current to the cathode is generated. A new method for evaluation of the ion current under such conditions is implemented. The developed model is applicable for cathode surface temperatures below the boiling point of the cathode material and may be used for multidimensional simulations of ignition of high-current arcs on refractory cathodes.

Revolutionizing multifunctional electrolyte additive design and synthesis for high-voltage nickel-rich batteries in diverse climates

The high-voltage LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode presents a promising avenue for advancing the energy density of lithium-ion batteries. Nevertheless, current limitations primarily arise from electrolyte systems unable to meet stringent criteria, including stable performance under elevated temperatures and efficient discharge at low temperatures. In this study, we address these challenges by designing a molecular structure incorporating boron oxygen functional groups, phenyl-, and fluorine moieties to simultaneously enhance ion conductivity and thermal stability under extreme voltages. A multifunctional electrolyte additive, 3, 4, 5-trifluorophenylboronic anhydride (TFPBA), has been successfully developed via synthesis. TFPBA plays a pivotal role in promoting the formation of a hierarchical cathode electrolyte interphase (CEI) through its preferential decomposition and oxidation processes. This CEI features a mechanically stable inner layer enriched with fluorophenyl- groups, crucial for high-temperature cycling, alongside an outer layer concentrated with BxOyFz complexes that significantly improve Li+ conductivity, ensuring superior performance under low-temperature conditions and at elevated rates. Moreover, TFPBA acts as an HF scavenger within the electrolyte, mitigating corrosive effects on the cathode surface, thereby curtailing CEI reformation and the transition metal dissolution. The Li/NCM622 half cells with TFPBA exhibit impressive capacity retention rates of 92.58%, 80.09%, and 81.77% after extensive cycling at temperatures of −20 °C, 25 °C, and 55 °C, respectively. Moreover, NCM622/graphite full cells with TFPBA achieve a remarkable capacity retention of 97.97% after 150 cycles at room temperature. Our findings highlight the exceptional electrochemical performance of NCM622 cathodes at elevated voltages across a wide temperature range, providing valuable insights for the development of advanced electrolytes in high-demand applications.

Bipolar electrochemical sensor with perylene diimide-based cathodic luminophore for dopamine detection and imaging

Bipolar electrochemical microscopy (BEM), which visualizes the concentration distribution of molecular species in biological systems by electrochemiluminescence (ECL), is expected to be applied to the high-spatiotemporal-resolution imaging of biomolecules, enabling the analysis of cellular functions. In the past, the molecular species that could be imaged by BEM were generally restricted to oxidized molecules due to the limitation derived from the ECL mechanism of the luminophore. Recently, the imaging of dopamine (DA), a reduced molecule, was achieved using Ru (bpy)32+/glutathione disulfide (GSSG) as a cathodic luminophore. However, a large driving voltage was required for ECL generation, resulting in a low S/N ratio. In this study, we employed N,N′-dimethyl-3,4,9,10-perylenetetracarboxylic diimide (PDI-CH3)/potassium peroxodisulfate (K2S2O8), which is a cathodic luminophore that can be reduced at a nobler potential to produce ECL than [Ru(bpy)3]2+/GSSG. First, the ECL mechanism of PDI-CH3/K2S2O8 was elucidated by using a PDI-CH3 drop-cast glassy carbon electrode (GCE) immersed in K2S2O8 solution as the working electrode in a 3-electrode system. The PDI-CH3 drop-casted GCE, a single closed bipolar electrode (c-BPE), was used as the cathode in the successful quantification of 50–500 μmol L−1 DA in a sample chamber in which a c-BPE anode was immersed, resulting in a high S/N. The selective detection of DA in the presence of ascorbic acid was achieved by modifying the anode with Nafion. Finally, DA imaging was demonstrated using a commercially available anisotropic conducting film with PDI-CH3 coating on the cathode surface as a c-BPE array. The change in the concentration distribution in the inflow of DA was successfully imaged based on the change in the ECL intensity at the c-BPE cathode. This BEM system is expected to be useful for DA imaging of the brain.

Effect of nitrogen-containing groups on the reduction of copper ions: In situ Raman and AIMD

In situ Raman spectroscopy and ab initio molecular dynamics (AIMD) were utilized to observe and analyze the micro-scale variations of levelers on the cathode surface. The cathodic polarization and charge transfer resistance of the three electroplating systems were examined using electrochemical methods. The throwing power of the printed circuit board coating and the nucleation changes at various times were investigated using an OLYMPUS confocal laser microscope and a scanning electron microscope. Based on the first-principles and AIMD calculations, the energy gaps, adsorption energies, and dynamic changes over 20 ps for the three levelers were determined, and the molecular mechanisms of action on the copper surface were analyzed to demonstrate alterations in the coating thickness. Experimental and theoretical results indicate that 2-thiazole-2-thiol possesses the strongest inhibitory energy, significantly repelling copper ions from migrating to the far end. On the surface, 4,6-dimethyl-2-pyrimidinethiol decomposes to form nitrogenous and sulfurous groups, which inhibit and adsorb copper ions. The adsorption states of the three levelers were thoroughly validated using Raman spectroscopy, corroborating the AIMD simulation results.

Origin of O2 Generation in Sulfide-Based All-Solid-State Batteries and its Impact on High Energy Density.

The cathode surface of sulfide-based all-solid-state batteries (SBs) is commonly coated with amorphous-LiNbO3 in order to stabilize charge-discharge reactions. However, high-voltage charging diminishes the advantages, which is caused by problems with the amorphous-LiNbO3 coating layer. This study has investigated the degradation of amorphous-LiNbO3 coating layer directly during the high-voltage charging of SBs. O2 generation via Li extraction from the amorphous-LiNbO3 coating layer is observed using electrochemical gas analysis and electrochemical X-ray photoelectron spectroscopy. This O2 leads to the formation of an oxidative solid electrolyte (SE) around the coating layer and degrades the battery performance. On the other hand, elemental substitution (i.e., amorphous-LiNbxP1- xO3) reduces O2 release, leading to stable high-voltage charge-discharge reactions of SBs. The results have emphasized that the suppression of O2 generation is a key factor in improving the energy density of SBs.

Surface nickel gradient tunes anionic redox activity to stabilize cobalt-free Li-rich cathodes

Constructing a gradient structure of transition metals is promising to improve the electrochemical performance of layered oxide cathodes. However, the nickel gradient spinel layer on the surface of layer Li-rich cathodes is barely successful. Herein, we present a refining strategy of reductive gas to induce a Ni-gradient spinel layer on the surface of Li1.2Mn0.6Ni0.2O2 (LRNMO). The formed gradient spinel layer stabilizes the coordination environment at the interface and reduces oxygen loss. Moreover, the Ni gradient further maintains the reversibility of the Mn3+/Mn4+ redox couple, while the multiple valence states of Mn ions in the gradient layer enhance the electrochemical kinetics. The LRNMO with Ni-gradient spinel layer achieves an initial coulomb efficiency reaching 86.1% and maintaining an energy density of 667.9 Wh kg−1 after 200 cycles at 1 C. The surface gradient strategy is conducive to maintaining structural stability and provides support for the continued development of Li-ion batteries.

Enhanced structural stability and durability in lithium-rich manganese-based oxide via surface double-coupling engineering

Lithium-rich manganese-based oxides (LRMOs) exhibit high theoretical energy densities, making them a prominent class of cathode materials for lithium-ion batteries. However, the performance of these layered cathodes often declines because of capacity fading during cycling. This decline is primarily attributed to anisotropic lattice strain and oxygen release from cathode surfaces. Given notable structural transformations, complex redox reactions, and detrimental interface side reactions in LRMOs, the development of a single modification approach that addresses bulk and surface issues is challenging. Therefore, this study introduces a surface double-coupling engineering strategy that mitigates bulk strain and reduces surface side reactions. The internal spinel-like phase coating layer, featuring three-dimensional (3D) lithium-ion diffusion channels, effectively blocks oxygen release from the cathode surface and mitigates lattice strain. In addition, the external Li3PO4 coating layer, noted for its superior corrosion resistance, enhances the interfacial lithium transport and inhibits the dissolution of surface transition metals. Notably, the spinel phase, as excellent interlayer, securely anchors Li3PO4 to the bulk lattice and suppresses oxygen release from lattices. Consequently, these modifications considerably boost structural stability and durability, achieving an impressive capacity retention of 83.4% and a minimal voltage decay of 1.49 mV per cycle after 150 cycles at 1 C. These findings provide crucial mechanistic insights into the role of surface modifications and guide the development of high-capacity cathodes with enhanced cyclability.

Effects of Ionic Interferents on Electrocatalytic Nitrate Reduction: Mechanistic Insight.

Nitrate, a prevalent water pollutant, poses substantial public health concerns and environmental risks. Electrochemical reduction of nitrate (eNO3RR) has emerged as an effective alternative to conventional biological treatments. While extensive lab work has focused on designing efficient electrocatalysts, implementation of eNO3RR in practical wastewater settings requires careful consideration of the effects of various constituents in real wastewater. In this critical review, we examine the interference of ionic species commonly encountered in electrocatalytic systems and universally present in wastewater, such as halogen ions, alkali metal cations, and other divalent/trivalent ions (Ca2+, Mg2+, HCO3-/CO32-, SO42-, and PO43-). Notably, we categorize and discuss the interfering mechanisms into four groups: (1) loss of active catalytic sites caused by competitive adsorption and precipitation, (2) electrostatic interactions in the electric double layer (EDL), including ion pairs and the shielding effect, (3) effects on the selectivity of N intermediates and final products (N2 or NH3), and (4) complications by the hydrogen evolution reaction (HER) and localized pH on the cathode surface. Finally, we summarize the competition among different mechanisms and propose future directions for a deeper mechanistic understanding of ionic impacts on eNO3RR.

Ionization processes of negative corona discharge. Part 2. Theory. Comparison with experiment

The purpose of the research is a theoretical analysis of ionization processes in the air, which are initiated by a high-voltage field generated by the negative needle-flat electrode electrode system. Methods. Fe, Cu, Al electrodes are used. Calculations are carried out using the methods of quantum mechanics and mathematical physics. Results. The processes of cold and thermoelectron emission of electrons, enhanced by an external high-voltage field (Schottky emission), are analyzed. The conditions under which the generation of charges from the cathode surface due to plasma-chemical reactions and the capture of surface electrons by electronegative oxygen molecules are decisive are investigated. Based on the PE theory, a theory of injection of negative ions from the cathode into an electronegative gas is constructed and the theory is compared with experiment. It has been shown that at small radii of curvature of needle tips, when E ≥ 106 V/cm, the generation of charges is due to cold emission of electrons. In average fields E ≈ 105 V/cm, electron emission is due to the Schottky effect. In fields E ≈ 104 V/cm and below, injection is caused by electrochemical processes and PE capture. A theory has been developed for PEs that appear at electric field intensities on the electrode of the order of several tens of kV/cm, that is, on flat and slightly curved negative electrodes. The capture of PE by electron-withdrawing molecules causes an injection current and, as a consequence, the ignition of a corona discharge. Analytical expressions for the surface density as a function of the local electric field strength, as well as an expression for the injection current, are obtained. The agreement between theory and experiment is satisfactory. Conclusion. An analysis of the development of CR on negative needles is given. A theory of PE at the cathode in strong electric fields was developed. Based on the results of measuring dark negative current-voltage characteristics, it is possible to determine the patterns of surface processes involving electronic transitions, in particular, determine the concentration of PE and injection currents.

Cobalt-vanadium coating deposition via programmed electrolysis mode

In the current work, the co-deposition of cobalt with vanadium from a complex citrate electrolyte via stationary and pulse electrolysis modes was investigated. The process was carried out at a current density of 1–15 Adm–2 in stationary electrolysis mode and 2–10 Adm–2 in pulse electrolysis mode, with variable ratio of pulse time to pause time at a temperature range of 35–400С and pH 3.0–3.5. According to the results of X-ray fluorescence spectrometry, the maximum content of vanadium in the coating obtained via the programmed electrolysis mode is 1.20–1.45%, which is tens of times higher than in the coating deposited by the stationary electrolysis mode (vanadium content of 0.007–0.017%) under similar conditions. The obtained results may confirm the hypothesis of additional vanadium reduction from oxo-anions by adsorbed hydrogen atoms formed on the cathode surface during the pause period. Based on the results of the analysis of 3D graphs, the optimal parameters of the process for fabricating a cobalt-vanadium coating with the maximum vanadium content in the alloy and a coating current efficiency of 80% have been established.

Electrochemical activation of peroxymonosulfate facilitated by a stainless-steel scrubber cathode: Transition from non-radical to radical pathway mediated by iron leaching

This study investigated the feasibility and underlying mechanisms of peroxymonosulfate (PMS) activation by a stainless-steel scrubber (SSS) cathode. Experimental findings revealed that the system could achieve 100 % degradation of sulfamethoxazole (SMX) in 30 min at initial pH value ranging from 3 to 9. The activation mechanism was observed to occur in two distinct stages. The first stage was characterized by a non-radical 1O2 dominance (0–6 min), where the activation of PMS and O2 was primarily facilitated through direct electron transfer at the cathode surface. Subsequently, the second stage transitioned to a radical dominance (6–18 min), with SO4− playing a pivotal role. This was attributed to the release of Fe2+ ions resulting from cathodic corrosion, which induced both homogeneous and heterogeneous Fenton-like reactions. The PMS/SSS cathode system exhibited anti-interference against most water matrices, except for HCO3−. Notably, the system demonstrated exceptional performance in the degradation of pollutants within phosphate wastewater samples, suggesting its potential for application in such contexts. In addition, the electrical energy was calculated to be 0.025 kWh·m−3 at a current of 0.01 A and a voltage of approximately 2.0 V, providing significant economic benefits.

Effective suppression of surface cation segregations on double perovskite oxides through entropy engineering

Cation segregation on cathode surfaces plays a key role in determining the activity and operational stability of solid oxide fuel cells (SOFCs). The double perovskite oxide PrBa0.8Ca0.2Co2O5+δ (PBCC) has been widely studied as an active cathode but still suffer from serious detrimental segregations. To enhance the cathode stability, a PBCC derived A-site medium-entropy Pr0.6La0.1Nd0.1Sm0.1Gd0.1Ba0.8Ca0.2Co2O5+δ (ME-PBCC) oxide was prepared and its segregation behaviors were investigated under different conditions. Compared with initial PBCC oxide, the segregations of BaO and Co3O4 on the surface of ME-PBCC material are significantly suppressed, especially for Co3O4, which is attributed to its higher configuration entropy. Our results also confirm the improved electrochemical performance and structural stability of ME-PBCC material, enabling it as a promising cathode for SOFCs.

A novel cathode interphase formation methodology by preferential adsorption of a borate-based electrolyte additive.

The coupling of high-capacity cathodes and lithium metal anodes promises to be the next generation of high-energy-density batteries. However, the fast-structural degradations of the cathode and anode challenge their practical application. Herein, we synthesize an electrolyte additive, tris(2,2,3,3,3-pentafluoropropyl) borane (TPFPB), for ultra-stable lithium (Li) metal||Ni-rich layered oxide batteries. It can be preferentially adsorbed on the cathode surface to form a stable (B and F)-rich cathode electrolyte interface film, which greatly suppresses the electrolyte-cathode side reactions and improves the stability of the cathode. In addition, the electrophilicity of B atoms in TPFPB enhances the solubility of LiNO3 by 30 times in ester electrolyte to significantly improve the stability of the Li metal anode. Thus, the Li||Ni-rich layered oxide full batteries using TPFPB show high stability and an ultralong cycle life (up to 1500 cycles), which also present excellent performance even under high voltage (4.8V), high areal mass loading (30mg cm-2) and wide temperature range (-30∼60°C). The Li||LiNi0.9Co0.05Mn0.05O2 (NCM90) pouch cell using TPFPB with a capacity of 3.1Ah reaches a high energy density of 420Wh kg-1 at 0.1C and presents outstanding cycling performance.

Molybdenum-Doped Cobalt-Free Cathode Realizing the Electrochemical Stability by Enhanced Covalent Bonding.

The doping strategy effectively enhances the capacity and cycling stability of cobalt-free nickel-rich cathodes. Understanding the intrinsic contributions of dopants is of great importance to optimize the performances of cathodes. This study investigates the correlation between the structure modification and their performances of Mo-doped LiNi0.8Mn0.2O2 (NM82) cathode. The role of doped Mo's valence state has been proved functional in both lattice structural modification and electronic state adjustment. Although the high-valence of Mo at the cathode surface inevitably reduces Ni valence for electronic neutrality and thus causes ion mixing, the original Mo valence will influence its diffusion depth. Structural analyses reveal Mo doping leads to a mixed layer on the surface, where high-valence Mo forms a slender cation mixing layer, enhancing structural stability and Li-ion transport. In addition, it is found that the high-valence dopant of Mo6+ ions partially occupies the unfilled 4d orbitals, which may strengthen the Mo─O bond through increased covalency and therefore reduce the oxygen mobility. This results in an impressive capacity retention (90.0% after 200 cycles) for Mo-NM82 cathodes with a high Mo valence state. These findings underscore the valence effect of doping on layered oxide cathode performance, offering guidance for next-generation cathode development.