Cathode Material For Sodium-ion Batteries Research Articles

Research of Cathode Materials for Sodium-Ion Batteries

Sodium-ion batteries are being extensively studied as a replacement for lithium-ion batteries in some areas. However, there are also some problems with cathode materials at present. Sodium-ion batteries perform worse performance than lithium-ion batteries, which is due to the properties of sodium. For instance, sodium ions possess a greater ionic radius and increased atomic weight compared to lithium ions. This piece presents an overview of the operational principles behind sodium-ion batteries, examining the preparation techniques, structure, and effectiveness of three main cathode materials. Moreover, the current challenges of cathodes and the corresponding solutions for sodium-ion batteries are systematically recognized. This article provides a new perspective or idea for solving the problem of sodium-ion battery cathode.

Surface structure reconstruction to suppress heterogeneous phase transformation for air-stable single crystalline O3-type sodium oxide

O3-type layered oxide cathode material for sodium-ion batteries (SIBs) has attracted much attention as one of the most viable candidates due to its high specific capacity and mature synthesis process, while the moisture sensitivity and harmful phase transformation lead to poor processing properties and unsatisfactory life-span, hindering its large-scale and commercial application. Herein, single crystallization strategy is adopted to enhance air stability and processing performance, and surface structure reconstruction for single crystalline cathode material O3-NaNi1/3Fe1/3Mn1/3O2 by ammonium tetraborate pretreatment is employed to further remove residual alkali and improve sodium ions diffusion dynamics and suppress heterogeneous phase transformation, achieving superior structure stability. Surface residual alkali is in-situ converted into a protective coating layer of Na2B4O7 and meanwhile partial B atoms enter into the interstitial site of sub-surface or near surface, which accelerates sodium ions transport as well as enhances TM-O bonding and hybridization of surface O (2p)-Fe (3d-t2g) orbital, inhibits TMO6 slabs gliding and strengthens structure on the surface and near surface. Additionally, the formed boron-rich surface exhibits high stability, effectively alleviating structural degradation from surface to bulk and enhancing air stability. Benefiting from the reconstructed surface structure, the modified single crystalline oxides (NFM@B) exhibit distinguished processing performance and electrochemical properties.

Six element high-entropy Prussian blue analogue cathode enabling high cycle stability for sodium-ion batteries

Prussian blue analogues (PBA) are promising cathode materials for sodium-ion batteries. However, the cycle life of PBA is limited due to its structure instability during cycling. Here, we successfully introduce six transition metals into N coordination site to increase the configurational entropy, significantly improving the structure stability and cycle life of PBA cathode materials. Electrochemical characterization methods are used to compare the behavior of hexa-, penta-, quadr-, and tri-metal PBA, exhibiting the characteristic of performance increasing with entropy. Time-resolved in situ X-ray diffraction confirms the “quasi-zero-strain” structure of H-PBA during desodiation/sodiation process. X-ray absorption spectroscopy and density functional theory calculations reveal that Mn, Fe, Co and Cu contribute the high capacity of H-PBA, while Ni and Zn stabilize the structure. The strategy will inspire new ideas in designing long life cathode materials with high capacity for sodium-ion batteries.

Breaking boundaries in O3-type NaNi1/3Fe1/3Mn1/3O2 cathode materials for sodium-ion batteries: An industrially scalable reheating strategy for superior electrochemical performance

To address the challenges of air stability and slurry processability in layered transition metal oxide O3-type NaNi1/3Fe1/3Mn1/3O2 (NFM) for sodium-ion batteries (SIBs), we have designed an innovative 500 °C reheating strategy. This method improves the surface properties of NFM without the need for additional coating layers, making it more efficient and suitable for large-scale applications. Pristine NFM (NFM-P) was first synthesized through a high-temperature solid-state method and then modified using this reheating approach (NFM-HT). This strategy significantly enhances air stability and electrochemical performance, yielding an initial discharge specific capacity of 151.46 mAh/g at 0.1 C, with a remarkable capacity retention of 95.04% after 100 cycles at 0.5 C. Additionally, a 1.7 Ah NFM||HC (hard carbon) pouch cell demonstrates excellent long-term cycling stability (94.64% retention after 500 cycles at 1 C), superior rate capability (86.48% retention at 9 C), and strong low-temperature performance (77% retention at −25 °C, continuing power supply at −40 °C). Notably, even when overcharged to 8.29 V, the pouch cell remained safe without combustion or explosion. This reheating strategy, which eliminates the need for a coating layer, offers a simpler, more scalable solution for industrial production while maintaining outstanding electrochemical performance. These results pave the way for broader commercial adoption of NFM materials.

Insights into Tiny High‐Entropy Doping Promising Efficient Sodium Storage of Na3V2(PO4)2O2F toward Sodium‐Ion Batteries

AbstractBoth high operation voltage and theoretical capacity promise polyanion‐type fluorophosphate Na3V2(PO4)2O2F as a competitive cathode toward high‐energy‐density sodium‐ion batteries (SIBs). However, the intrinsic low kinetic characteristics seriously influence its high‐power property and service life. To well address this, a creative tiny high‐entropy (HE) doping methodology is purposefully developed to fabricate nanoscale Na3V1.94(Cr, Mn, Co, Ni, Cu)0.06(PO4)3O2F (NVPOF‐HE) as the advanced cathode materials for SIBs. The grain refinement effect induced by collaborative regulations from polyvinyl pyrrolidone and tiny HE heteroatomic doping is reasonably proposed for nanosizing particle dimension of NVPOF‐HE. Systematic experiments and theoretical calculations authenticate that the HE doping efficiently promotes the electronic/ionic transport and high‐voltage capacity contribution, and weakens the lattice expansion over Na+‐(de)intercalation processes. Thanks to the appealing virtues mentioned here, the nano NVPOF‐HE, compared to single‐ion/dual‐ion/triple‐ion doped cases, achieves even better Na+‐storage performance in terms of both high‐rate capacities and long‐term cycling stability. Furthermore, the NVPOF‐HE assembled full SIBs deliver a high materials‐level energy density of 463 Wh kg−1 and electrochemical stability of ≈93.8% capacity retention after 1000 cycles at 5 C rate. More essentially, the fundamental insights gained here provide a significant scientific and technological advancement in high‐performance and durable polyanionic cathodes toward next‐generation SIBs.

STUDYING THE ELECTROCHEMICAL PROPERTIES OF POTASSIUM-DOPED SODIUM-MANGANESE OXIDE CATHODE MATERIALS FOR SODIUM-ION BATTERIES

The development of layered sodium manganese oxide cathode materials with high capacity and long life is one of the keys to boosting the performance of sodium-ion batteries (SIBs), but it remains a great challenge. In this work, a potassium doped P2-type sodium manganese oxide, Na0.8K0.1Mn0.9O2 (NKMO), is developed as a high-capacity and long-lasting cathode for high-performance SIBs. Sodium-potassium-manganese oxide Na0.8K0.1Mn0.9O2 was synthesized by a conventional solid-state reaction method. Crystal structure and morphology of the NKMO material were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The NKMO material was utilized to fabricate CR2032-type coin cells, and later evaluated for its electrochemical characteristics. The electrochemical characteristics of NKMO were evaluated through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charging-discharging (GCD) at different current densities on a NEWARE battery testing system. The NKMO material had a superior initial charge and discharge capacity, approximately 130 mAh.g-1 and 125 mAh.g-1, respectively, within the voltage range of 1.5-4 V at a current density of 0.1 C. Remarkably, the capacity remained stable at 100 mAh.g-1 even after 100 cycles. These findings indicate that NKMO is a highly promising cathode material for sodium-ion batteries.

Internal doping and surface coating: Mn / La-HCF @ Fe-HCF composites as high-performance cathode materials for sodium-ion batteries

Internal doping and surface coating: Mn / La-HCF @ Fe-HCF composites as high-performance cathode materials for sodium-ion batteries

A two-pronged approach:Bulk-phase substitution and second-phase synergism to enhance the anion redox stability of layered oxide cathode for sodium-ion batteries

As a supplement to lithium-ion batteries, sodium-ion batteries have great application potential in large-scale energy storage equipment, vehicle start-stop power supplies, and low-speed electric vehicle power. P3-NaxLiyMn1-yO2 (NLMO), has received widespread attention due to its higher charge voltage and discharge capacity. However, poor cycle stability and rapid voltage platform decay caused by the release of oxygen during charging hinder its practical application. This paper reports a new NLMO modification strategy, which effectively improves the cycling stability of NLMO by substituting Zr4+ for Mn4+ in the bulk phase to suppress the O2−/On− redox couple activity and stabilize the ZrO2 second phase lattice. Under the combined action of substitution and second phase, the capacity retention rate of NLMO@Zr0.15 was 85.4 % after 100 cycles at a rate of 5 C. The results show that Zr4+ changes the coordination environment and electronic structure of O in the crystal lattice, prompting further splitting of Mn t2 g, thereby increasing the proportion of Mn 3d orbitals near the Fermi level. During the first discharge process, due to the charge balancing effect, Mn3+/Mn4+ replaced the electrochemical activity of O2−/On−, obtaining a specific capacity of up to 161 mAh g−1. This internal and external improvement idea provides a new direction for solving the poor cycle stability of NLMO high specific energy sodium-ion battery cathode materials and improving the specific capacity.

Zero-Strain Sodium Nickel Ferrocyanide as Cathode Material for Sodium-Ion Batteries with Ultra-Long Lifespan.

Prussian blue analogues are recognized as one of the most promising cathode materials for sodium-ion batteries (SIBs) owing to the open 3D framework structure with large interstitial sites and developed Na-ion diffusion channels. However, high content of anion vacancy and poor structural stability have hampered the prospect of their application. In this work, sodium nickel ferrocyanide (Na1.34Ni[Fe(CN)6]0.92, NNHCF) is proposed as cathode material for SIBs. N-coordinated Ni-ion can boost NNHCF to possess less Fe[(CN)6]4- defect, low Na-ion migration barrier, and more negative formation energy compared with Na0.91Cu[Fe(CN)6]0.77 (NCHCF), thus exhibiting more active sites, fast electrochemical kinetics behavior and great structure stability. It is confirmed that NNHCF undergoes a solid solution mechanism without phase evolution for reversible Na-ion intercalation/deintercalation, employing Fe associated with C atom as redox center for charge compensation. Therefore, NNHCF contributes a high initial energy density of 180.94 Wh·g-1 at 10 mA·g-1, excellent rate capability, superior cycling stability with ultra-long lifespan of 13000 cycles, and low fading rate of 0.0027% per cycle at 500 mA·g-1. This work sheds light on the construction of low-defect PBA cathodes with outstanding dynamics and stability.

Charge-Compensation-Driven Failure Mechanism of Ni Redox in Fe-Rich Ni/Fe/Mn-Based O3-Type Layered Oxide Sodium-Ion Cathodes.

For cathode materials of sodium-ion batteries, O3-type Ni/Fe/Mn-based (Na-NFM) layered oxides have garnered extensive attention because of high economic viability, environmental friendliness, and the potential for high energy density. Among them, Fe-rich compositions exhibit higher initial charge capacity and lower bill-of-material costs, while they fade rapidly and exhibit low initial coulombic efficiency, hindering their commercialization prospects. In this work, we investigate the failure of Fe-rich Na-NFM materials through X-ray absorption spectroscopy methods. The results reveal a combined failure mechanism that encompasses not only the conventional theory of Fe migration but also an abnormal Ni-redox deterioration, which has not yet been reported. More factors related to the failure of Fe-rich Na-NFM layered oxides are discussed in detail. These findings are expected to inspire targeted research efforts toward Fe-rich Na-NFM materials, thereby accelerating the practical application of sodium-ion batteries.

Progress and Prospects in Cathode Materials for Sodium-Ion Batteries: Synthesis, Characterization, and Engineering Aspects

Progress and Prospects in Cathode Materials for Sodium-Ion Batteries: Synthesis, Characterization, and Engineering Aspects

High-Entropy Layered Oxide Cathode Materials with Moderated Interlayer Spacing and Enhanced Kinetics for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) with low cost and environmentally friendly features have recently attracted significant attention for renewable energy storage. Sodium layer oxides stand out as a type of promising cathode material for SIBs owing to their high capacity, good rate performance, and high compatibility for manufacturing. However, the poor cycling stability of layer oxide cathodes due to structure distortion greatly impacts their practical applications. Herein, a high entropy doped Cu, Fe, and Mn-based layered oxide (HE-CFMO), Na0.95Li0.05Mg0.05Cu0.20Fe0.22Mn0.35Ti0.13O2 for high-performance SIBs, is designed. The HE-CFMO cathode possesses high-entropy transition metal (TM) layers with a homogeneous stress distribution, providing a moderated interlayer spacing to maintain the structure stability and enhance Na+ ion diffusion. In addition, Li doping in TM layers increases the Mn valence state, which effectively suppresses John-Teller effect, thus stabilizing the layered structure during cycling. Furthermore, the use of nontoxic and low-cost raw materials benefits future commercialization and reduces the risk of environmental pollution. As a result, the HE-CFMO cathode exhibits a super cycling performance with a 95% capacity retention after 300 cycles. This work provides a promising strategy to improve the structure stability and reaction kinetics of cathode materials for SIBs.

Suppressing vacancies and crystal water of sodium manganese iron-based Prussian blue analogue by potassium doping for advanced sodium-ion batteries

Sodium manganese iron-based Prussian blue analogue (MnFe-PBAs) is regarded as potential cathode material for sodium-ion batteries due to its simple synthesis process, low production cost, and high theoretical capacity. Unfortunately, electrochemical performances of MnFe-PBAs are inevitably hindered owing to the crystal vacancies and crystal water produced from aqueous co-precipitation process. Herein, highly crystallized cubic potassium-doped sodium manganese iron-based Prussian blue analogue is synthesized by a modified co-precipitation method. By introducing a larger ionic radius potassium (K) to substitute the part of Na in the MnFe-PBAs, a coexistence composite of sodium and potassium phases is obtained with less crystal water and fewer vacancies compared with pure sodium phase compound, resulting that potassium-doped sodium manganese iron-based Prussian blue analogue (Na1.08K0.74Mn[Fe(CN)6]0.86⋅□0.14⋅1·.86H2O, NaKMHCF) can deliver high discharge specific capacity (129.3 mAh/g at 10 mA g−1), excellent rate performance (82.3 mAh/g at 1500 mA g−1) as well as high cycling stability (77.0 % capacity retention at 500 mA g−1 after the 500th cycle). Besides, the full cell, based on NaKMHCF as cathode material and sodium titanium phosphate (NTP) as anode material, confirms its potential as high-performance cathode material for SIBs.

Maximizing the Structural Stability of the Na-Rich Prussian Blue Analogue Electrode through Charge Cutoff Voltage Regulation.

Prussian blue and its analogues (PB/PBAs) are promising sodium-ion battery cathode materials due to their easy synthesis and excellent discharge capacity. However, their low structural stability poses a challenge. One critical factor affecting stability is the charge cutoff voltage. Increasing this voltage can enhance lithium-ion battery capacity but may reduce cycle retention due to intensified electrode-electrolyte interface reactions. This study investigates whether this phenomenon also applies to sodium-ion batteries and proposes an optimal voltage to improve both the capacity and stability. By cycling between 3.8 and 4.2 V, the charge/discharge profiles and redox reaction intensity were analyzed. The correlation between structural stability and charge cutoff voltage was re-evaluated based on these findings. An optimal charge cutoff voltage of 4.1 V was identified, creating an additional plateau during initial charging and altering Na+ ion positioning to enhance capacity. Enhanced mobility of ions and electrons was observed through a stable solid-electrolyte interphase (SEI) formation. Ex situ X-ray diffraction (XRD) confirmed reversible phase transitions and excellent structural stability. This study underscores the strategic use of charge cutoff voltage to enhance both discharge capacity and structural stability, offering insights for advancing PB/PBA cathode materials with improved stability and capacity.

Atomic-scale probing of ion migration dynamics in Na3Ni2SbO6 cathode for sodium ion batteries

Honeycomb-layered phases like Na3Ni2SbO6 have been extensively researched as high-voltage and high-rate capability cathode materials for sodium-ion batteries. However, our understanding of the structural stability and dynamic reaction mechanisms of Na3Ni2SbO6 cathode during cycling, especially at atomic-scale, remains limited. Here, we track the microstructure evolution during extraction of Na+ ions in Na3Ni2SbO6 cathode at atomic scale in an aberration-corrected transmission electron microscope. The electron beam irradiation that can provide a driving force for the Na+ ion migration, allows us to mimic the battery charge process. By controlling the electron beam dose, we study the structure evolution behavior to obtain insights into understanding the work principle and failure mechanism of Na3Ni2SbO6 cathode under different charge rate conditions. We find that the real-time structural evolution and ion migration pathways of Na3Ni2SbO6 cathode are distinct under different electron beam doses. High-dose irradiation reveals Na ion depletion, surface cracks, and phase transformations, mimicking rapid capacity decay. In contrast, low-dose irradiation shows slower ion migration, ordered Na vacancy formation, and maintaining structural integrity, which more closely resembles the electrochemical process of actual battery. This study provides an atomistic understanding of the structural stability and Na ions deintercalation mechanism in Na3Ni2SbO6 cathodes, offering new insights into optimizing electrode materials.

Roles of fast-ion conductor NaAlO2 modifying P2-Na0.67Ni0.3Mn0.6Co0.1O2 cathode material for sodium-ion batteries

P2-type layered oxides are promising candidates for sodium-ion batteries. However, structural instability and sluggish Na⁺ diffusion kinetics hinder their further commercialization. In this study, NaAlO2, which possesses a similar α-NaFeO2 layer structure, is coated onto the surface of P2-Na0.67Ni0.3Mn0.6Co0.1O2 (NNMC) to enhance its electrochemical performance as a novel cathode for sodium-ion batteries. A variety of experimental results and characterizations reveal that the thin NaAlO2 coating layer significantly reduces side reactions and facilitates the diffusion of Na⁺ at the interface between the cathode and the electrolyte. Moreover, the introduction of partial Al ions into the transition-metal layers enlarge the interlayer spacing, and decrease the content of Mn3+. As a result, the NNMC cathode material, modified with 3 wt% NaAlO2, demonstrated remarkable electrochemical performance. The initial specific discharge capacity was recorded at 137.7 mA h g−1 at 0.2 C, and an impressive discharge capacity of 38.2 mA h g−1 was attained at 20 C. Following 100 cycles at a rate of 0.5 C, the capacity retention rate was determined to be 99.6 %.

Tuning Na Occupation and Annealing Temperature on Na Diffusion Pathways in P2-Type NaxNi0.25Mn0.75O2 for Sodium-Ion Batteries by Ab Initio Calculations.

The NaxNi0.25Mn0.75O2 cathode material draws ongoing interest owing to its considerable specific capacity along with its elevated average operating voltage. However, its application is limited by weak rate performance and quick capacity fading. In this study, a series of NaxNi0.25Mn0.75O2 (x = 0.65, 0.70, 0.75, 0.80) cathode materials are prepared by the solid-phase method based on an orthogonal experiment. The optimum preparation process is investigated by optimizing factors such as Na content, calcination temperature, calcination time, and heating rate. The Nae/Naf ratio is adjusted, and the Na+ at different sites are rearranged to reduce the Na+/vacancy ordering by changing the Na content on the basis of process optimization. Owing to the fast migration kinetics of Nae sites, experimental results indicate that the P2-Na0.75Ni0.25Mn0.75O2 cathode material, which has Na+ occupying more thermodynamically stable Nae sites, demonstrates superior battery performance. High initial discharge specific capacity (157.2 mAh g-1) along with favorable cycle performance of the Na0.75Ni0.25Mn0.75O2 cathode material can be achieved by modifying the Nae site occupancy and optimizing the experimental conditions. Together with the microscopic control of Na+ occupancy, this novel orthogonal experiment design offers a fresh perspective and approach to a thorough comprehension of cathode materials for sodium-ion batteries.

A phase transition coordinated monoclinic Fe-based Prussian blue for high-performance sodium-ion battery cathode

Prussian blue analogs (PBAs) are ideal cathode materials for sodium-ion batteries (SIBs) owing to their cost-effectiveness, good low-temperature performance, and facile synthesis process. Nevertheless, their actual capacity and cycling stability limit practical application. Herein, a new chelating agent, sodium tartrate, is proposed to synthesize high-quality Fe-based Prussian blue (HQ-NFF) with enhanced Na content and a stable structure through chelation effect-assisted co-precipitation. The crystal structure of HQ-NFF undergoes a phase transition to a Na-rich monoclinic phase after full discharge, leading to improved capacity and cycling stability. The HQ-NFF cathode exhibits an ultra-high capacity of 160.8 mAh g−1 and a capacity of 146.1 mAh g−1 at 2 C, with a capacity retention of 75.3 % after 150 cycles. Moreover, a 3D-printed HQ-NFF cathode with an areal loading of 7.88 mg cm−2, delivers a high areal capacity of 0.969 mAh cm−2 and good rate capability.

Pr6O11 modification effectively enhancing sodium storage for Na3V2(PO4)3 batteries

Na3V2(PO4)3 (NVP) is one of the most promising cathode materials for sodium-ion batteries (SIBs) due to its robust three-dimensional framework, high tunability, and relatively high Na+ intercalation potentials. However, its utility is generally constrained by low conductivity, inefficient charge transfer, and subpar interface kinetics. This work presents an efficient and simple method to address these issues. We innovatively modified the NVP surface with Pr6O11 nanoparticles, a negative temperature coefficient (NTC) thermosensitive material, to enhance interface compatibility with electrolytes and improve conductivity. This modification significantly enhances the overall sodium-ion storage performance. Specifically, the optimized NVP-2 %Pr6O11 electrode exhibits excellent electrochemical properties with the aid of an optimized conductivity network compared to the unmodified NVP. Cycled at an 8C current density, the NVP-2 %Pr6O11 electrode achieves high specific capacities of 102.6 mAh·g−1 at 27 °C and 95.6 mAh·g−1 at 45 °C. After 1000 cycles, the capacity retention rates are 81.18 % and 78.97 %, respectively, significantly higher than the 20.59 % and 14.99 % of pure NVP. In coin full-battery testing, the NVP-2 %Pr6O11 electrode retains 89.76 % capacity after 500 cycles at 8C. In addition, the assembled The NVP-2 %Pr6O11//HC pouch full battery exhibits better sodium-ion storage and thermal safety performance compared to the NVP-SP//HC battery. This simple modification strategy provides an effective insight into the application of NVP electrodes in energy storage.

Improving the Performance of the Layered Nickel Manganese Oxide Cathode of Sodium-Ion Batteries by Direct Coating with Sodium Niobium Oxide.

This research highlights the efficacy of NaNbO3 as a coating for P2-Na2/3Ni1/3Mn2/3O2 cathodes in sodium-ion batteries. The coating enhances the kinetic behavior and cyclability of the electrochemical cells, as shown by electrochemical measurements. XRD analysis indicates that Nb does not incorporate into the cathode structure, implying a physical interaction between the coating and the cathode material. XRF analysis and EDX mapping confirm the actual composition and uniform dispersion of elements throughout the sample, while the electron micrographs evidence the occurrence of NaNbO3 particles modifying the surface of the layered oxide. The Ni4+/Ni3+ and Ni3+/Ni2+ redox pairs, along with the partially reversible oxidation of oxide to peroxide anions, contribute significantly to cell capacity, as revealed by XPS spectra. This last effect and the appearance of a co-intercalated phase at high voltage are positive factors to provide fast kinetics. Cyclic voltammograms show that samples coated with 2-3% NaNbO3 have superior rate capability, with high capacitive response and apparent diffusion coefficients. These samples also have low impedance at the electrode-electrolyte interface, which helps deliver a high capacity at 5C. Further cycling at 1C shows improved cyclability in the bare and 3% coated samples, due to their higher diffusion coefficients on charging. Notably, the 3% NaNbO3-coated sample exhibits excellent cyclability below 0 °C, making it a promising cathode material for sodium-ion batteries.