Cathode Material For Sodium-ion Batteries Research Articles

Achieving a Deeply Desodiated Stabilized Cathode Material by the High Entropy Strategy for Sodium-ion Batteries.

Manganese-based layered oxides are currently of significant interest as cathode materials for sodium-ion batteries due to their low toxicity and high specific capacity. However, the practical applications are impeded by sluggish intrinsic Na+ migration and poor structure stability as a result of Jahn-Teller distortion and complicated phase transition. In this study, a high-entropy strategy is proposed to enhance the high-voltage capacity and cycling stability. The designed P2-Na0.67Mn0.6Cu0.08Ni0.09Fe0.18Ti0.05O2 achieves a deeply desodiation and delivers charging capacity of 158.1 mA h g-1 corresponding to 0.61 Na with a high initial Coulombic efficiency of 98.2%. The charge compensation is attributed to the cationic and anionic redox reactions conjunctively. Moreover, the crystal structure is effectively stabilized, leading to a slight variation of lattice parameters. This research carries implications for the expedited development of low-cost, high-energy-density cathode materials for sodium-ion batteries.

Ion Dynamics at the Intermediate Charging State of the Sodium Vanadium Fluorophosphate Cathode.

Na super ionic conductor (NASICON)-type polyanionic vanadium fluorophosphate Na3V2O2(PO4)2F (NVOPF) is a promising cathode material for high-energy sodium-ion batteries. The dynamic diffusion and exchange of sodium ions in the lattice of NVOPF are crucial for its electrochemical performance. However, standard characterizations are mostly focused on the as-synthesized material without cycling, which is different from the actual battery operation conditions. In this work, we investigated the hopping processes of sodium in NVOPF at the intermediate charging state with 23Na solid-state nuclear magnetic resonance (ssNMR) and density functional theory (DFT) calculations. Our experimental characterizations revealed six distinct sodium coordination sites in the intermediate structure and determined the exchange rates among these sites at variable temperatures. The theoretical calculations showed that these dynamic processes correspond to different ion transport pathways in the crystalline lattice. Our combined experimental and theoretical study uncovered the underlying mechanisms of the ion transport in cycled NVOPF and these understandings may help the optimization of cathode materials for sodium-ion batteries.

Unveiling the potential of Na2FePO4F@PEG composite as cathode material for sodium-ion batteries

Unveiling the potential of Na2FePO4F@PEG composite as cathode material for sodium-ion batteries

Ti-doped O3-NaNi0.5Mn0.5O2 as high-performance cathode materials for sodium-ion batteries

With favorable electrochemical activity, NaNi0.5Mn0.5O2(NNMO) has been a key cathode material in sodium-ion batteries. However, the phase-transition irreversible and kinetics sluggish issues in NaNi0.5Mn0.5O2 greatly limit its application in sodium-ion batteries. Here, various Ti-doped O3-NaNi0.5Mn0.5-xTixO2 cathode materials were fabricated via solid-phase method. The extra Ti-doping treatment effectively stabilized the transition layer of metal and enlarged the Na layer spacing, as well as suppressed the Na+/vacancy ordering. In particular, the obtained O3-NaNi0.5Mn0.46Ti0.04O2 (NNMOTi-4) exhibits initial reversible capacity of 108.6 mAh g−1 at 0.1C and remarkable 65.2% capacity retention after 100 cycles at 1C. Accordingly, this work provides a facile Ti-doping strategy to regulate the structure and electrochemical performance of layered NaxTMO2 for sodium-ion batteries.

Prussian Blue Analogues for Sodium-Ion Battery Cathodes: A Review of Mechanistic Insights, Current Challenges, and Future Pathways.

Prussian blue analogues (PBAs) have emerged as highly promising cathode materials for sodium-ion batteries (SIBs) due to their affordability, facile synthesis, porous framework, and high theoretical capacity. Despite their considerable potential, practical applications of PBAs face significant challenges that limit their performance. This review offers a comprehensive retrospective analysis of PBAs' development history as cathode materials, delving into their reaction mechanisms, including charge compensation and ion diffusion mechanisms. Furthermore, to overcome these challenges, a range of improvement strategies are proposed, encompassing modifications in synthesis techniques and enhancements in structural stability. Finally, the commercial viability of PBAs is examined, alongside discussions on advanced synthesis methods and existing concerns regarding cost and safety, aiming to foster ongoing advancements of PBAs for practical SIBs.

Dual-ion regulation of coordination chemistry for high-voltage stabilized P2-type cathode

P2-Na2/3Ni1/3Mn2/3O2 has shown great potential as cathode material for sodium-ion batteries with its high theoretical capacity and energy density. However, severe structural changes are induced by charging P2-Na2/3Ni1/3Mn2/3O2 above 4.2 V, resulting in rapid capacity decay and poor kinetic capability. In this study, we propose a Zn/Ti synergistic modification strategy to stabilize the P2-type cathode under high voltage. It is found that the P2-O2 phase transition with large volume change is replaced by a milder P2-Z phase transition with the noteworthy improvement in structural stability and Na+ diffusion kinetics, due to the disordered Na+/vacancy and the suppressed of the sliding of transition metal layers, as disclosed by density functional theory calculations and in-situ X-ray diffraction. Concurrently, The phenomenon of Ni and O reductive coupling is inhibited by regulating local O coordination owing to the incorporation of a strong Ti−O covalence bond, leading to the more reversible charge compensation mechanism and the inhibited lattice O evolution, as clearly revealed by ex-situ X-ray absorption spectroscopy and Differential Electrochemical Mass Spectrometry. Consequently, we obtained a stable P2-Na0.67Zn0.05Ni0.28Mn0.52Ti0.15O2 cathode, achieving an average discharge voltage of 3.62 V at 0.1 C and a capacity retention of 80% after 500 cycles at 2 C. This research provides valuable insights into the enhancement of sodium-ion battery cathode materials by utilizing different functional ions in synergy.

Continuous Flow Electrochemical Synthesis of Olivine-Structured NaFePO4 Cathode Material for Sodium-Ion Batteries from Recycle LiFePO4.

To mitigate the environmental impact of the improper disposal of spent LiFePO4 batteries and reduce resource waste, the development of LiFePO4 recycling technologies is of paramount importance. Meanwhile, olivine-structured NaFePO4 in sodium-ion batteries has received great attention, due to its high theoretical specific capacity of 154 mAh g-1 and excellent stability. However, olivine NaFePO4 only can be synthesized from olivine LiFePO4. Accordingly, in this proposal, developing the continuous flow electrochemical solid-liquid reactor-based metal ion insertion technology is to utilize the olivine FePO4, recycled from LiFePO4, and to synthesize NaFePO4. Additionally, by employing I- as the reducing agent, NaFePO4 is successfully synthesized with a discharge-specific capacity of 134 mAh g-1 at 0.1C and a remarkable capacity retention rate of 86.5% after 100 cycles at 0.2C. And the reasons for sodium deficiency in the synthesized NFP are elucidated through first-principles calculations. Furthermore, the kinetics of the solid-solution reaction 2 (Na2/3+βPO4→ Na1-αFePO4) mechanism improve with cycling and are sensitive to temperature. Utilizing a minimal amount of reducing agent in the electrochemical reactor, NaFePO4 synthesis is successfully achieved. This innovative approach offers a new, cost-effective, and environmentally friendly strategy for preparing NaFePO4 from recycling LiFePO4.

P2-type layered oxide cathode with honeycomb-ordered superstructure for sodium-ion batteries

Sodium-ion batteries (SIBs) have been proved as one of the most alternative to Lithium-ion batteries (LIBs) by the virtue of the abundant resources of Na. Among the cathodes, layered oxides stand out owing to their high energy density. The Jahn–Teller distortion, structural phase transition and oxygen release are main drawbacks of Mn/Ni based layered oxides. Hence, Li-Ni-Cu co-substituted Na0.67Li0.1(Mn0.7Ni0.2Cu0.1)0.9O2 (NLMNC) sample was prepared. The NLMNC sample exhibits the honeycomb-ordered superstructure at about 22° which is ascribed to cation ordering. By virtue of the Li-Ni-Cu co-substitute, the Jahn–Teller distortion of Mn is suppressed. Attributed to Li+ migrating from the metal oxide layer to the interlayer and the Li+ can play the part of pillar in the interlayer, NLMNC cathode displays the capacity retention rate of 82.5 % at 200 mA g−1 after 100 cycles. The anionic redox reaction of NLMNC is related to the addition of Li ions and O 2p non-bonding which is different from the anionic redox reaction of electrons removing from O 2p in the eg* (Ni–O) states of Na2/3Ni1/3Mn2/3O2. During charge process, peroxo O− emerges with the oxidation of lattice oxygen. During discharge process, the intensity of peroxo O− gradually decreases. DFT calculations were also carried out to reveal the reaction mechanism of NLMNC. The DFT results showed that the anionic redox reaction occurs near Mn ions, while the Ni ions are stable which is corresponding with our results. It is proven that such Li-Ni-Cu co-substituted NLMNC presents a promising cathode material for SIBs.

Preparation of N-doped carbon-modified Na3V2(PO4)2F3 based on ZIF-8 as a template and its electrochemical properties

N-doped porous carbon material (N-PC) was generated through high-temperature cracking, using ZIF-8 as a template, and preparation of Na3V2(PO4)2F3/N-PC composites were designed and prepared as cathode materials for sodium-ion batteries, and the electrochemical sodium storage performance was systematically investigated. The physical characterization results showed that the addition of N-PC played a role in increasing the electrical conductivity of Na3V2(PO4)2F3 material and improving the specific surface area. The electrochemical test results showed that the discharge specific capacity of Na3V2(PO4)2F3/N-PC composite was 109.56 mAh/g at 0.1C, and the capacity retention rate was 85.10 % after 100 cycles, and the RSEI of Na3V2(PO4)2F3/N-PC composite (81.55 Ω) is better than that of Na3V2(PO4)2F3 pure-phase material (142.5 Ω), which indicates that the ion transfer impedance of the modified material has been effectively reduced, and the ion de-embedding is more fluent.

Compositing pine pollen derived carbon matrix with Na4FeV(PO4)3 nanoparticle for cost-effective sodium-ion batteries cathode

Na super-ion conductor type material Na3V2(PO4)3 has been widely researched as the cathode of sodium-ion batteries (SIBs) in recent years, but the unsatisfying cost of Na3V2(PO4)3 impedes its wide application in SIBs. In this study, iron element is used to replace part of vanadium in Na3V2(PO4)3 to reduce its expense, and pine pollen is applied for the first time as a very effective carbon source to improve the performance of Na4FeV(PO4)3. The fabricated composite material achieves a capacity of 105 mA h g−1 under 0.2 C and fascinating cycling stability over 94 % under 2 C for 500 cycles and 98 % under 10 C for 1000 cycles. The excellent cycle performance is caused by the involvement of pine pollen that acts as a carbon matrix to enhance the electron conductivity and block the agglomeration of active material effectively, thus the well-dispersed nano sized Na4FeV(PO4)3 shortens the diffusion path of sodium ion and gains a remarkable rate capability. Moreover, the distinguished reversibility during the charge and discharge procedures is ascribed also to the robust structure of Na4FeV(PO4)3. This work provides an efficient route to realize the economic cathode material of SIBs with good performance.

Design of Na3MnZr(PO4)3/Carbon Nanofiber Free-Standing Cathodes for Sodium-Ion Batteries with Enhanced Electrochemical Performances through Different Electrospinning Approaches.

The NASICON-structured Na3MnZr(PO4)3 compound is a promising high-voltage cathode material for sodium-ion batteries (SIBs). In this study, an easy and scalable electrospinning approach was used to synthesize self-standing cathodes based on Na3MnZr(PO4)3 loaded into carbon nanofibers (CNFs). Different strategies were applied to load the active material. All the employed characterization techniques (X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), and Raman spectroscopy) confirmed the successful loading. Compared to an appositely prepared tape-cast electrode, Na3MnZr(PO4)3/CNF self-standing cathodes demonstrated an enhanced specific capacity, especially at high C-rates, thanks to the porous conducive carbon nanofiber matrix. Among the strategies applied to load Na3MnZr(PO4)3 into the CNFs, the electrospinning (vertical setting) of the polymeric solution containing pre-synthesized Na3MnZr(PO4)3 powders resulted effective in obtaining the quantitative loading of the active material and a homogeneous distribution through the sheet thickness. Notably, Na3MnZr(PO4)3 aggregates connected to the CNFs, covered their surface, and were also embedded, as demonstrated by TEM and EDS. Compared to the self-standing cathodes prepared with the horizontal setting or dip-drop coating methods, the vertical binder-free electrode exhibited the highest capacity values of 78.2, 55.7, 38.8, 22.2, 16.2, 12.8, 10.3, 9.0, and 8.5 mAh/g at C-rates of 0.05C, 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, and 20C, respectively, with complete capacity retention at the end of the measurements. It also exhibited a good cycling life, compared to its tape-cast counterpart: it displayed higher capacity retention at 0.2C and 1C, and, after cycling 1000 cycles at 1C, it could be further cycled at 5C, 10C, and 20C.

Co-free and low strain cathode materials for sodium-ion batteries: Machine learning-based materials discovery

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) owing to their cost-effectiveness and similar intercalation mechanisms. Layered transition metal oxides (LTMOs) are the promising cathode candidates for SIBs owing to their high voltages and ease of synthesis. However, O3-type LTMOs undergo structural deformation and performance degradation during de-/intercalation. Owing to the limitations of single-element compounds, doping them with various elements can enhance their stability and performance. In this study, machine learning (ML) algorithms are used to predict the structural stability of O3-type materials without phase transitions to facilitate efficient material selection. ML classification models assess the phase stability of cathodes in the pristine and desodiated states. Data sampling and feature engineering enhanced the accuracy of the pristine model from 0.886 to 0.962 and desodiated model from 0.642 to 0.954. Furthermore, a novel database in the form of NaxNi0.5MayMbzO2 (0.5 ≤ x ≤ 1, y + z = 0.5; M = transition metal) was constructed using density functional theory (DFT) calculations. Out of 1,451 LTMOs candidates, we present 128 cathode candidates that satisfy the following conditions: (1) O3 phase is maintained during dis-/charging processes, (2) average voltage ≥ 3 V, (3) theoretical capacity ≥ 200 mAh/g, and (4) -5 % ≤ volume change ≤ 5 %. Among them, 125 materials showed the possibility of stable Co-free cathodes, and 13 materials exhibited -0.5 % < volume change < 0.5 %. This study suggests optimal LTMO candidates that satisfy both the high energy density and electrochemical stability and provides a reliable battery material screening platform.

A document-level information extraction pipeline for layered cathode materials for sodium-ion batteries

Natural language processing techniques enable extraction of valuable information from large amounts of published literature for the application of data science and technology, i.e. machine learning in the field of materials science. Nevertheless, the automated extraction of data from full-text documents remains a complex task. We propose a document-level natural language processing pipeline for literature extraction of comprehensive information on layered cathode materials for sodium-ion batteries. The pipeline enhances entity recognition with contextual supplementary information while capturing the article structure. Finally, a heuristic multi-level relationship extraction algorithm is employed in relation extraction to extract experimental parameters and complex performance relationships respectively. We successfully extracted a comprehensive dataset containing 5265 records from 1747 documents, encompassing essential information such as chemical composition, synthesis parameters, and electrochemical properties. By implementing our pipeline, we have made significant progress in overcoming the challenges associated with data scarcity in battery informatics. The extracted datasets provide a valuable resource for further research and development in the field of layered cathode materials.

A Rhombic 2D Conjugated Metal-Organic Framework as Cathode for High-Performance Sodium-Ion Battery.

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have garnered significant attention as promising electroactive materials for energy storage. However, their further applications have been hindered by low capacity, limited cycling life, and underutilization of the active sites. Herein, we introduce Cu-TBA (TBA = octahydroxyl tetrabenzoanthracene) with large conjugation units (narrow energy gap) and a unique rhombus topology as the cathode material for sodium-ion batteries (SIBs). Notably, Cu-TBA with a rhombus topology exhibits a high specific surface area (613 m2 g-1) and metallic band structure. Additionally, Cu-TBA outperforms its hexagonal counterpart, Cu-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxyphenanthrene), demonstrating superior reversible capacity (153.6 mAh g-1 at 50mA g-1) and outstanding cyclability with minimal capacity decay even after 3,000 cycles at 1 A g-1. This work elucidates a new strategy to enhance the electrochemical performance of 2D c-MOFs cathode materials by narrowing the energy gap of organic linkers, effectively expanding the utilization of 2D c-MOFs for SIBs. This article is protected by copyright. All rights reserved.

Toward Ultrahigh Rate and Cycling Performance of Cathode Materials of Sodium Ion Battery by Introducing a Bicontinuous Porous Structure.

The emerging sodium-ion batteries (SIBs) are one of the most promising candidates expected to complement lithium-ion batteries and diversify the battery market. However, the exploitation of cathode materials with high-rate performance and long-cycle stability for SIBs has remained one of the major challenges. To this end, an efficient approach to enhance rate and cycling performance by introducing an ordered bicontinuous porous structure into cathode materials of SIBs is demonstrated. Prussian blue analogues (PBAs) are selected because they are recognized as a type of most promising SIB cathode materials. Thanks to the presence of 3D continuous channels enabling fast Na+ ions diffusion as well as the intrinsic mechanical stability of bicontinuous architecture, the resultant PBAs exhibit excellent rate capability (80 mAh g-1 at 2.5 A g-1) and ultralong cycling life (>3000 circulations at 0.5Ag-1), reaching the top performance of the reported PBA-based cathode materials. This study opens a new avenue for boosting sluggish ion diffusion kinetics in electrodes of rechargeable batteries and also provides a new paradigm for solving the dilemma that electrodes' failure due to high-stress concentration upon ion storage.

Capacitive-Controlled Prussian White with a Nickel Iron Hexacyanoferrate Composite Cathode for Rapid Sodium Diffusion.

Prussian blue analogues receive tremendous attention owing to their spacious three-dimensional skeleton, high theoretical specific capacity, facile synthesis procedure, and high cost-effectiveness as among the most promising candidates for cathode materials in sodium-ion batteries (SIBs). Nonetheless, the practical specific capacity, especially under high current, is particularly frail due to the sluggish ion diffusion. In this study, the strategy of Ni substitution and formation of water-coordinated Fe is applied to lower the crystal field energy and elevate the active low-spin (LS) Fe content, which leads to a capacitive sodium storage mechanism, resulting in a substantial specific capacity under high current density. The delivered specific capacity of PW-325@2NiFe-55 is 95 mAh g-1 at 50 C, which is 72.5% capacity retention of the one at 0.5 C. Also, it maintains 80.2% of its initial specific capacity after 500 cycles at 5 C. Furthermore, a hypothesis of a joint diffusion-controlled and capacitive mechanism for high-spin (HS) Fe and a mere capacitive mechanism for LS Fe is put forward and verified through potentiastatic tests, operando 57Fe Mössbauer spectroscopy, and ex situ XRD, which provides a new horizon to enhance the electrochemical performance for SIBs.

Exploration of mixed polyanionic compound for potential high-voltage cathode materials in sodium-ion batteries

Exploration of mixed polyanionic compound for potential high-voltage cathode materials in sodium-ion batteries

Ultrafine Mn-rich P2-type Na0.67Fe0.1Mn0.9O2 particles via combustion synthesis as high-performance sodium-ion battery cathode

Layered transition metal oxide is considered as one of the most promising cathode materials for sodium-ion batteries due to the abundant reserves of Na, Fe, and Mn. Moreover, the trivalent Fe substitution weakens the Jahn–Teller effect and enhance the crystal structure during the de/intercalation of Na+. Herein, a series of Mn-rich P2-type Na0.67Fe0.1Mn0.9O2 (NFMO-600, NFMO-700 and NFMO-800) are prepared using combustion synthesis followed by calcinating at 600, 700 and 800 °C, respectively. As confirmed by XRD and SEM, NFMO-700 owns ultrafine high-purity crystal particles with a larger layer spacing and a smaller crystal size. Owing to these unique structures, NFMO-700 exhibits excellent electrochemical performance, delivering an impressive 179 mA h g−1 at 0.2C, with a capacity retention of 84.43 % after 100 cycles at 0.5C.

Hollow Layered Iron-Based Prussian Blue Cathode with Reduced Defects for High-Performance Sodium-Ion Batteries.

Fe-based Prussian blue (Fe-PB) analogues have emerged as promising cathode materials for sodium-ion batteries, owing to their cost-effectiveness, high theoretical capacity, and environmental friendliness. However, their practical application is hindered by [Fe(CN)6] defects, negatively impacting capacity and cycle stability. This work reports a hollow layered Fe-PB composite material using 1,3,5-benzenetricarboxylic acid (BTA) as a chelating and etching agent by the hydrothermal method. Compared to benzoic acid, our approach significantly reduces defects and enhances the yield of Fe-PB. Notably, the hollow layered structure shortens the diffusion path of sodium ions, enhances the activity of low-spin Fe in the Fe-PB lattice, and mitigates volume changes during Na-ion insertion/extraction into/from Fe-PB. As a sodium-ion battery cathode, this hollow layered Fe-PB exhibits an impressive initial capacity of 95.9 mAh g-1 at a high current density of 1 A g-1. Even after 500 cycles, it still maintains a considerable discharge capacity of 73.1 mAh g-1, showing a significantly lower capacity decay rate (0.048%) compared to the control sample (0.089%). Moreover, the full cell with BTA-PB-1.6 as the cathode and HC as the anode provides a considerable energy density of 312.2 Wh kg-1 at a power density of 291.0 W kg-1. This research not only enhances the Na storage performance of Fe-PB but also increases the yield of products obtained by hydrothermal methods, providing some technical reference for the production of PB materials using the low-yield hydrothermal method.

A Stable High-Potential Na7V4(P2O7)4(PO4) Cathode for Sodium-Ion Batteries Developed from a Water-Based Slurry

The sodium mixed-phosphate polyanionic compound Na7V4(P2O7)4PO4 (NVPP) is an attractive high-potential cathode material for sodium-ion batteries. In this study, a water-soluble binder, namely polyacrylic acid (PAA), was used to successfully process NVPP-based electrodes. In the absence of toxic and expensive organic solvents, the fabrication scenario of our NVPP-PAA electrode appears as a more sustainable and cost-effective approach for slurry processing and electrode production. Supported by detailed electrochemical investigations, we highlight the excellent electrochemical performance of the NVPP-PAA electrodes, which show capacity retention of ∼97% after 200 cycles at a high current density (3 C) in addition to its attractive rate capability with minimal electrode polarization up to 5 C rate.