Cathode Material For Sodium-ion Batteries Research Articles

Optimizing interfacial modification for enhanced performance of Na3V2(PO4)3 cathode in sodium-ion batteries

A novel cathode material, Na3V2(PO4)3C@CNT (NVP/C@CNT), was designed and synthesized by a low-temperature solid-phase drying ball milling method. The nanoparticles are covered by an amorphous carbon layer, and simultaneously enveloped and embedded by carbon nanotubes on the surface. Consequently, a carbon network consisting of carbon nanotubes and amorphous carbon layers is formed in the material. Notably, no phase transition during the intercalation process of sodium ions, confirming the stable crystal structure, which ensures the stability and reversibility of the large-capacity cathode in the large-volume change. The addition of CNTs can regulate the size of NVP particles, increase the contact area between NVP and electrolyte, leading to an enhancement in the sodium ion diffusion coefficient. The NVP/C@CNT electrode exhibits a capacity of 114.5 mA h g−1 at 0.1 C. After 2650 cycles, the discharge capacity retention rate is 98.2 % at 10C. Even at 20 C, the discharge capacity is still 93.3 mA h g−1 after 2710 cycles, with a retention rate of 99.5 %. This work provides a feasible approach for the design of low-cost, long-life, high-performance cathode materials for sodium-ion batteries.

Design and fabrication of nitrogen-doped graphene-promoted Na3MnTi(PO4)3@C cathode with three-electron reactions for sodium-ion storage

As a novel cathode material for sodium-ion batteries, Na3MnTi(PO4)3 (denoted as NMTP) has received great attention because of its abundant natural resources, excellent safety, low toxicity as well as three-electron reactions. Unfortunately, the pure NMTP cathode displays a bad conductivity, resulting in an inferior electrochemical performance for sodium energy storage. Herein, we introduce a good route to fabricate the nitrogen-doped graphene-decorated NMTP@C (denoted as NG-NMTP@C) composite with superior rate property and superior cycle stability for the first time. In this fabricated material, the nitrogen-doped graphene nanosheets are dispersed into the NMTP@C particles. Compared to NMTP@C, the prepared NG-NMTP@C cathode possesses better cycle stability and higher capacity. It shows the capacity of 173.1 mAh g−1 at 0.1 C and presents the high capacity retention of around 97.1 % at 10.0 C over 400 cycles. Therefore, this fabricated NG-NMTP@C nanocomposite can be employed as the novel positive electrode in sodium-ion storage.

High-entropy doping NASICON[sbnd]Cathode breaks the kinetic barriers and suppresses voltage hysteresis for sodium ion batteries

The NASICON-type Na3MnTi(PO4)3 material has garnered widespread attention for its stable three-dimensional structure, rapid sodium-ion transport channels and excellent thermal stability. However, its poor electronic conductivity, cyclic stability and structural decay during cycling have posed significant obstacles to its commercialization. Herein, a high-entropy doping Na3.12MnTi0.9(VFeMgCrZr)0.02(PO4)3 cathode was successfully synthesized, exhibiting a high reversible capacity of 169.6 mAh g-1 and a high energy density of over 500 Wh kg-1. The DFT and machine learning MD results show that benefiting from the high-entropy effect of multi-element synergy in HE-NMTP, the electronic conductivity and sodium ion diffusion kinetics are significantly improved. Simultaneously, the voltage hysteresis and energy loss are mitigated, while crystal structural stability is improved. Furthermore, the full-cell achieves an impressive energy density of 440 Wh kg-1 (for cathode) at 0.2C. These results demonstrate the advantages of the high-entropy doping cathode as a potential cathode material for sodium-ion batteries and provide a valuable strategy for other NASICON system cathodes as well as polyanion cathodes.

High entropy Prussian Blue Analogues assisted by reduced graphene oxide for enhancing the lifespan of Sodium-ion batteries

In recent years, Prussian blue analogues (PBAs) have been regarded as one of the most promising cathode materials for Sodium-ion batteries (SIBs) due to their open structure, low cost, and high theoretical capacity. However, the problem of capacity degradation caused by phase transitions during the charge/discharge process has so far limited the applicability of PBAs. While the high entropy strategy can alleviate capacity decay induced by phase transitions, challenges such as low conductivity, material aggregation, and severe interface reactions between electrode materials and electrolytes still persist. Therefore, we used a simple and scalable one-step co-precipitation method to grow high entropy Prussian blue analogues (HEPBA) on reduced graphene oxide (rGO) to address these problems. The rGO not only inhibits material agglomeration but also separates the electrolyte from the electrode material to prevent severe interface reactions. Meanwhile, the Warburg impedance is reduced and the Na+ diffusion performance is improved. When high entropy Prussian blue grown on an rGO matrix (HEPBA@rGO) is utilized as the cathode in a half-cell, it exhibits high discharge specific capacity (115.2 mAh g−1 at 100 mA g−1), long cycling stability (retaining 84.6 mAh g−1 after 1000 cycles), and good rate capability (62 mAh g−1 at 15 C). The full battery with HEPBA@rGO as the cathode and hard carbon as the anode has a high specific discharge capacity (100.12 mAh g−1 at 100 mA g−1), good stability (capacity retention rate of 81 % after 150 charge/discharge cycles), and good rate performance (72.5 mAh g−1 at 5 C). This study provides valuable insights for the development of SIBs.

Study on the influence of different manganese sources on the formation of P2/β Bi-phase cathode materials for sodium ion batteries

This work focuses on the effect of the of Mn3+/Mn4+ ratio in the reactants on the structure and electrochemical properties of NaMn0.9Cu0.1O2 cathode materials for sodium-ion batteries. By systematically varying the manganese valence states in the reactants, we observed a phase transition from the β-phase to the P2-phase with increasing Mn3+ concentrations in the reactants, contrary to the expected favorability of the β-phase at higher Mn3+ levels. This finding suggests a complex interplay between the valence states of the reactants and phase formation mechanisms, which needs further investigation. Additionally, electrochemical testing indicated that the phase composition significantly impacts the electrochemical performance of the material. Specifically, the M0 sample, possessing the optimal P2/β ratio, exhibited excellent electrochemical performances, achieving a high initial discharge capacity of 155.1 mA h g−1 and remains 88.1 % after 40 cycles. These results emphasize the importance of precursor selection and valence management in the development of high-performance cathode materials for sodium-ion batteries.

Pyrene-4,5,9,10-tetraone-based covalent organic framework/carbon nanotube composite as sodium-ion cathodes with high-rate capability

Covalent organic frameworks (COFs) have attracted significant interest in the field of rechargeable batteries on account of their unique properties, including robust frameworks, well-defined porosity, abundant redox-active sites, and flexible structure designability. However, the limited active site utilization and low electrical conductivity always bring about poor electrochemical performance, thereby hindering practical applications. Herein, we reported a pyrene-4,5,9,10-tetraone-based covalent organic framework composite (Tp-PTO-COF@CNTs) grown on multi-walled carbon nanotubes via in-situ polycondensation. The Tp-PTO-COF@CNTs with numerous active sites (C=O groups) and strong π-π interaction between CNTs and COFs could accommodate more Na-ions and boost structural stability. Moreover, the existence of 1D CNTs could improve electronic conductivity, which facilitates fast transport of electrons and enhances reaction kinetics. In view of the two synergistic effects, Tp- PTO-COF@CNTs cathode displays an outstanding sodium-ion storage property with high initial capacity of 223.2 mA h/g at 0.1 A/g, remarkable rate capability at as high as 20 A/g, and ultra-long cycling stability (163.0 mA h/g exceeding 5000 cycles at 5 A/g). Furthermore, the ex-situ measurements are proposed to better confirm the role of carbonyl groups as redox-active centers. Such ultra-stable structural advantage might inspire the development of COF cathode materials for sodium-ion batteries.

Cu/F Dual-Doping on the Ni–Mn Based Layered Oxide As Cathode Material for Sodium-Ion Batteries

As demands for energy storage are ever-increasing, sodium ion batteries (SIB) have been widely conducted for superior electrochemical performance and reduction in cost compared to lithium ion batteries (LIBs), one of the most commonly used energy storage devices nowadays. Among all the parts in batteries, cathode materials play a crucial role with regard to performance. Here, layered transition metal oxides (LTMOs) (NaxTMO2, TM = Cu, Mn, Fe, Ti, Co, Cr, Ni, etc.) have kept catching researchers’ eyes due to their mature developments in commercial LIBs over decades.P2-type Ni/Mn-based LTMOs (such as Na0.67Ni0.33Mn0.67O2, NNMO) exhibit high theoretical specific capacity (~173 mAh g− 1) with environmentally friendly and cheap elements. However, they show limited stability upon charging over 4.2 V, directly restricting their energy density and lowering operating voltage. Besides, disadvantages such as poor rate performance and air/moisture sensitivity are remaining improvements for commercialization. Hence, our study mainly focuses on improvements for shortages of NNMO by applying a facile cation-and-anion co-doping strategy. Via transition metal Cu ion doping, the cycling stability of NNMO can be improved without sacrificing too much capacity, and the air stability can also be improved. In addition, F doping to replace oxygen can further enhance the structural stability and increase the rate performance by modifying interlayer spacing of the layered structure. A facile sol-gel method with heat treatment is used to synthesize cation-and-anion co-doped NNMO. The material characterization shows successful synthesis after cation and anion doping. In addition, the long cycle test shows that capacity retention increases from ~50% to ~90% over 100 cycles after Cu doping. The specific discharge capacity also increases from ~110 mAh/g to ~130 mAh/g at 0.1C with a slight increase in cycle retention from ~75% to ~77% after F doping. Also, the capacity at 20C could be maintained at ~50 mAh/g, around 45% of the initial capacity at 0.1C. The detailed charge storage mechanism will be studied by applying operando X-ray absorption spectroscopy and ex-situ X-ray photoelectron spectroscopy. As for the moisture sensitivity part, the XRD spectra indicate that no noticeable structural changes or impurity formation occurred after air exposure for one month, showing good air stability. Furthermore, operando XRD is conducted to confirm structural reversibility during charging and discharging.In summary, by applying a simple Cu/F co-doping strategy, Na0.67Ni0.13Cu0.20Mn0.67O2-xFx exhibits sufficient cycle stability for over 100 cycles as well as excellent rate capability even at a high current density of 20C, which proves itself a promising candidate as high-performance cathode material in SIBs. In addition, the cheap and environmentally friendly elemental usage (Ni, Mn and Cu) and air-stability enhancement also increase possibility of this material for large-scale energy storage application in industry.

Carbon-Interconnected Sodium Vanadium Phosphate Microparticles: Material Characterizations and Na+-Storage Performances

Sodium vanadium phosphate (Na3V2(PO4)3) with continuous carbon-coating (NVP/C) has been regarded as one of the most promising cathode materials for sodium-ion batteries (SIBs) owing to the three-dimensional sodium superionic conductor (NASICON) structure for fast sodium-ion migrations, high theoretical energy density (ca. 400 Wh/kg), and good thermal stability (450°C). In this study, carbon-interconnected NVP/C microparticles (C@NVP/C MPs) were successfully synthesized by employing ascorbic acid and sodium-containing polymer as dual carbon sources, followed by calcination at 750°C in an argon atmosphere. The resulting C@NVP/C MPs not only exhibited great crystallinity, high purity, and size of 5-10 μm but also possessed carbon amounts of 9.9 wt. %, as confirmed through the X-ray diffractometer, scanning electron microscope, and thermogravimetric analyzer, respectively. The cyclic voltammogram revealed that the potential difference between oxidation and reduction peaks of C@NVP/C (174 mV at 0.1 mV/sec and 382 mV at 1.0 mV/sec) was less than that of the NVP/C nanoparticles (197 mV at 0.1 mV/sec and 391 mV at 1.0 mV/sec) that were synthesized without adding the sodium-containing polymer. Moreover, the same reversible capacity was delivered from C@NVP/C, i.e., 75 mAh/g at 0.1 C. Those improved electrochemical performances could be attributed to the well-interconnection between NVP/C and carbon originating from the pyrolysis of sodium-containing polymer, creating additional electronic transportation pathways. Accordingly, the C@NVP/C MPs synthesized in the present study are reasonably anticipated to be promising cathode materials for SIBs.

Optimizing O3-Type Fe-Mn-Based Cathodes for Na-Ion Batteries: Unveiling the Synergistic Impact of Chemical Co-Substitution

Layered transition metal oxide-Na x MO2 (M = transition metal) is the most widely explored class of cathode materials in lithium and sodium-ion batteries (LIBs and SIBs).1 The replacement of expensive Co and Ni with cheaper elements like Fe and Mn is appealing, which can reduce the overall cost of the battery. Despite the higher operating voltage of Fe3+/Fe4+ and the large specific capacity of Mn3+/Mn4+, issues like irreversible Fe-migration and J. T. distortion of Mn3+/Mn4+ are yet to be overcome.2,3 To improve the electrochemical performances of layered oxide cathodes, various cationic substitutions (e.g., Li+, Cu2+, Mg2+, Zn2+, and Ti4+) are partially substituted in the place of M.4–6 Along this line, in search of better Fe/Mn-based cathodes, we selected an O3-type Na[Fe0.50Mn0.50]O2 (NFMO) material and co-substituted Li+ and Cu2+ in the transition metal layer to create a composition of Na[LixCuyFe0.50-x-yMn0.50]O2 (NCLFMO) and compared their electrochemical performances.. Both materials crystallize in a rhombohedral structure and Rietveld refinement and TEM analyses suggest an enhanced O-Na-O spacing after substitution. The NFMO and NCLFMO cathodes display a capacity of 135 and 121 mAh g-1 in the potential window of 4.0–2.0 V at 0.1 C rate, with an average voltage (Vavg) of 2.63 V and 3.31 V respectively, which leads to an increased energy density of 400 Wh kg-1 for NCLFMO.7 Following substitution, the capacity contributions of Mn and Fe become 20.2% and 79.8%, respectively, instead of 49.8% and 50.2% in NFMO. Clearly, it indicates a pronounced Fe4+/Fe3+ redox activity with a suppressed J. T. distortion for Mn4+/Mn3+ redox. Chemical co-substitution significantly improves capacity retention, with NCLFMO retaining 98% of its initial discharge capacity after 500 cycles, compared to 52% for NFMO. Better rate capability, faster diffusion coefficient of Na+ ions from GITT, and reduced cell resistance from impedance spectroscopy support the enhanced performances of NCLFMO. In-situ XRD measurement reveals a reversible O3-P3-O’3-P3-O3 phase transition and ex-situ x-ray absorption spectroscopy analysis confirms a prominent Fe4+/Fe3+ redox with a suppressed Mn4+/Mn3+ redox during charge-discharge cycling. More significantly, NCLFMO remains air-stable, retaining its structure and electrochemical properties after exposure to air for 30 days. Finally, a full cell with precycled HC is constructed, delivering a capacity of 105 mAh g-1 with a Vavg of 3.15 V in the potential window of 4.0-1.5 V at a 0.1 C rate. In conclusion, the (Li + Cu)-co-substitution strategy improves the overall performance of the Fe-Mn-based layered oxide cathode, paving the way for developing better cathodes for commercialized SIBs. References J. Y. Hwang, S. T. Myung, and Y. K. Sun, Chem. Soc. Rev., 46, 3529–3614 (2017).S. Komaba, N. Yabuuchi, T. Nakayama, A. Ogata, T. Ishikawa and I. Nakai, Inorg. Chem., 51, 6211–6220 (2012).B. Mortemard De Boisse, J. H. Cheng, D. Carlier, M. Guignard, C. J. Pan, S. Bordère, D. Filimonov, C. Drathen, E. Suard, B. J. Hwang, A. Wattiaux and C. Delmas, J. Mater. Chem. A, 3, 10976–10989 (2015).L. Yang, X. Li, J. Liu, S. Xiong, X. Ma, P. Liu, J. Bai, W. Xu, Y. Tang, Y. Y. Hu, M. Liu and H. Chen, J. Am. Chem. Soc., 141, 6680–6689 (2019).G. Singh, N. Tapia-Ruiz, J. M. Lopez Del Amo, U. Maitra, J. W. Somerville, A. R. Armstrong, J. Martinez De Ilarduya, T. Rojo and P. G. Bruce, Chem. Mater., 28, 5087–5094 (2016).L. Wang, Y. G. Sun, L. L. Hu, J. Y. Piao, J. Guo, A. Manthiram, J. Ma and A. M. Cao J. Mater. Chem. A, 5, 8752–8761 (2017).A. Ghosh, R. Hegde, K. Kumar and P. Senguttuvan, J. Am. Chem. Soc., submitted(2023).

Unraveling the Role of Li and Mg Substitution in Layered Sodium Oxide Cathodes for Sodium-Ion Batteries.

Substituting electrochemically active elements such as Li and Mg in P2-type layered sodium oxide is an effective strategy for developing competitive cathode materials for sodium-ion batteries. However, the lack of atomic-level understanding regarding the distribution of substitution positions complicates the comprehension of the roles of substituting atoms and the mechanism of sodium-ion intercalation. In this study, we identified the stable configurations of Na in Na0.75Ni0.3Mn0.7O2 and Na0.75Li0.15Mg0.05Ni0.1Mn0.7O2 materials using the site exclusion method. Through simulating the complete charging process for both materials, the structure evolution of the cathodes during the cycling and the impact of the partial substitution of Ni elements by Li and Mg atoms were comprehensively elucidated. Our findings revealed that Mg atoms effectively regulate the distribution of forces within the materials, essentially serving as supportive pillars within the cathode. Meanwhile, Li atoms efficiently mitigated electron localization, consequently diminishing volume fluctuations during the charging process. More importantly, the substitution with Li and Mg atoms could synergistically reduce the interaction between transition metals and sodium ions, thereby reducing the diffusion energy barrier of Na ions. This study not only enhances the comprehension of substituted metal atoms in P2 layered oxides but also offers new insights for the development of sodium-ion cathode materials.

A high-entropy cathode for sodium-ion batteries: Cu/Zn-doping O3-Type Ni/Fe/Mn layer oxides

The O3 layered oxides have been extensively investigated as cathode materials for sodium-ion batteries due to their remarkable theoretical capacity. However, the large radius of Na+ lead to complex phase transitions and tortuous diffusion channels during extraction/insertion, which ultimately restricts the Na+ diffusion kinetics and cyclic stability. In this study, we report a Zn and Cu co-doping strategy to the high entropy layer oxide Na [Ni0·2Fe0·2Mn0·4Cu0·15Zn0.05]O2 (HEO-CuZn) using the sol-gel method to prepare the oxides. Here, Zn is used to stabilize the structure of layer between the transition metal and O atoms, which slows down the adverse phase transition. In the fabricated sample, the element Cu provides additional capacity and inhibits excessive oxidation. The prepared HEO-CuZn used as cathode for Na+ ion battery exhibits better electrochemical performance, delivering a high specific capacity of 148 mA h g−1, and 84 % capacity retention after 100 cycles, which is attributed to the expanded Na+ transfer channels, reduced activation energy and interface side reactions, thus enhancing the Na+ diffusion kinetics. Meanwhile, the high entropy strategy stabilizes the overall structure by reducing the John-Teller distortion and suppressing the Na+/vacancy order, and effectively avoids adverse phase transitions such as O′3 and P′3. This study provides a new insight for the advance of the next generation high specific energy sodium-ion battery.

Improved Electrochemical Performance of NASICON Type Na3V2-xCox(PO4)3/C (x = 0-0.15) Cathode for High Rate and Stable Sodium-Ion Batteries.

In recent years, the Na-ion SuperIonic CONductor (NASICON) based polyanionics are considered pertinent cathode materials in sodium-ion batteries due to their 3D open framework, which can accommodate a wide range of Na content and can offer high ionic conductivity with great structural stability. However, owing to the inferior electronic conductivity, these materials suffer from unappealing rate capability and cyclic stability for practical applications. Therefore, in this work we investigate the effect of Co substitution at the V site on the electrochemical performance and diffusion kinetics of Na3V2-xCox(PO4)3/C (x = 0-0.15) cathodes. All the samples are characterized through Rietveld refinement of the X-ray diffraction patterns, Raman spectroscopy, transmission electron microscopy, etc. We demonstrate improved electrochemical performance for the x = 0.05 electrode with a reversible capacity of 105 mAh g-1 at 0.1 C. Interestingly, the specific capacity of 80 mAh g-1 is achieved at 10 C with retention of about 92% after 500 cycles and 79.5% after 1500 cycles and having nearly 100% Coulombic efficiency. The extracted diffusion coefficient values through the galvanostatic intermittent titration technique and cyclic voltammetry are found to be in the range of 10-9 to 10-11 cm2 s-1. The post-mortem studies show excellent structural and morphological stability after testing for 500 cycles at 10 C. Our study reveals the role of optimal dopant of Co3+ ions at the V site in improving the cyclic stability at a high current rate.

Electrochemical Na+/K+ Ion Exchange in Zeolitic Vanadium(IV) Borophosphate K1.33Na0.67[VO(B2O)(PO4)2(HPO4)]·1.63H2O as Cathode Material for Sodium-Ion Batteries.

Electrochemical ion exchange has recently been demonstrated to be a unique method for the preparation of novel cathode materials, which cannot be accessible by traditional direct synthesis routes. In this study, the vanadium borophosphate compound K1.33Na0.67[VO(B2O)(PO4)2(HPO4)]·1.63H2O (KNVBP) with zeolitic framework exhibits fast electrochemical Na+/K+ ion exchange when used as cathode material in sodium-ion batteries (SIBs). Ex situ structural analyses and electrochemical measurements confirm that most of the K+ ions in the parent KNVBP can be extracted and exchanged by Na+ ions after the first charge/discharge cycle. The in situ-generated Na-rich phase shows reversible electrochemical activity at approximately 3.9 V versus Na+/Na with a specific capacity of 52.9 mAh g-1, comparable to 96.2% of the theoretical capacity. Moreover, enhanced ionic diffusion kinetics can be achieved after the Na+/K+ exchange. This study provides a valuable insight into the electrochemical ion exchange in polyanion compounds toward application in metal-ion batteries.

Gradient doping–induced triphasic intergrowth hexacyanoferrate cathode for high-performance sodium-ion batteries

As a high-capacity, high-voltage, and low-cost cathode material for sodium-ion batteries (SIBs), Na/Mn-based hexacyanoferrates (NaxMn[Fe(CN)6]1−y·□y·nH2O) typically exhibit poor structural reversibility and interfacial stability during cycling. In this study, we report the in-situ construction of a triphasic intergrowth Na/Mn/Zn-based hexacyanoferrate (mcr-Zn0.2Mn0.8) with concentration-gradient Zn distribution by an anion-controlled fractional precipitation route. Density functional theory calculations verify that the unique heterostructure arises from the different binding energies between cations and anions. A small amount of Zn2+ doping in the inner cubic/monoclinic phases enhances their structural reversibility during cycling by impeding lattice deformation induced by the Jahn–Teller effect of Mn3+. Meanwhile, the rhombohedral Zn-based hexacyanoferrate epitaxially grown on the surface diminishes the particle size of mcr-Zn0.2Mn0.8 resulting in short Na+ diffusion distance, and provides interface protection that suppresses detrimental electrolyte decomposition. Consequently, mcr-Zn0.2Mn0.8 exhibits a high discharge capacity of 121.1 mAh/g at 15 mA g−1, improved cycling stability at 750 mA g−1 with a capacity retention of 65.0 % after 2000 cycles, and enhanced rate capability with a discharge capacity of 71.4 mAh/g at 6000 mA g−1. The successful implementation of simultaneous surface and bulk modifications through a one-step reaction opens new possibilities for developing high-performance hexacyanoferrate cathode materials for SIBs.

Co and F co-doping to augmenting the electrochemical performance of P2-type sodium lithium manganese oxide for sodium ion battery

P2-type sodium lithium manganese oxide is recognized as one of the most promising cathode materials for sodium-ion batteries (SIBs). However, its practical application has been hindered by poor cycling performance and limited rate capacity. In this study, we successfully co-doped cobalt (Co) and fluorine (F) into P2-type sodium lithium manganese oxide, resulting in the enhanced material CoF-NLM, which significantly improves its electrochemical performance. The CoF-NLM material exhibits several advantageous characteristics: (i) a notable increase in lattice constant and lattice cell volume, which facilitates the intercalation and deintercalation of sodium ions within its bulk structure; (ii) an enhanced surface morphology that promotes better contact between the electrode and the electrolyte; and (iii) an increased Mn3+/Mn4+ ratio, which enhances the number of active transition metal centers available for electrochemical reactions. As a result, the CoF-NLM sample demonstrates exceptional electrochemical performance, boasting a specific capacity of 135.51 mAh/g at a current density of 8 mA g−1 and maintaining an impressive 92.69 % capacity retention after 100 cycles. This study conclusively demonstrates that ion doping is a highly effective strategy for enhancing the electrochemical performance of cathode electrode materials in SIBs; paving the way for the development of high-energy, high-power SIBs that can meet the demands of next-generation energy storage applications.

Air-Stable High-Entropy Layered Oxide Cathode with Enhanced Cycling Stability for Sodium-Ion Batteries.

O3-type layered oxides have been extensively studied as cathode materials for sodium-ion batteries due to their high reversible capacity and high initial sodium content, but they suffer from complex phase transitions and an unstable structure during sodium intercalation/deintercalation. Herein, we synthesize a high-entropy O3-type layered transition metal oxide, NaNi0.3Cu0.05Fe0.1Mn0.3Mg0.05Ti0.2O2 (NCFMMT), by simultaneously doping Cu, Mg, and Ti into its transition metal layers, which greatly increase structural entropy, thereby reducing formation energy and enhancing structural stability. The high-entropy NCFMMT cathode exhibits significantly improved cycling stability (capacity retention of 81.4% at 1C after 250 cycles and 86.8% at 5C after 500 cycles) compared to pristine NaNi0.3Fe0.4Mn0.3O2 (71% after 100 cycles at 1C), as well as remarkable air stability. Finally, the NCFMMT//hard carbon full-cell batteries deliver a high initial capacity of 103 mAh g-1 at 1C, with 83.8 mAh g-1 maintained after 300 cycles (capacity retention of 81.4%).

Insights into magnesium and titanium co-doping to stabilize the O3-type NaCrO2 cathode material for sodium-ion batteries

Insights into magnesium and titanium co-doping to stabilize the O3-type NaCrO2 cathode material for sodium-ion batteries

Multimodal High-Throughput Approach Assisted by Deep Learning for the Analysis of Ceramic Saggars

The ceramic saggar is a container utilized in the production process of cathode materials for sodium-ion or lithium-ion batteries, and the characterization of saggar damage mechanisms often relies on the analysis of microstructure and composition of micro-sized areas. However, these results are often unreliable as they derive from a limited amount of data and cannot thus be utilized to perform a comprehensive and accurate analysis of the corrosion resistance mechanism of the saggar. In this study, deep learning combined with multimodal high-throughput in situ characterization methods, including array-SEM, μ-XRF, and μ-XRM, is employed to comprehensively analyze the multiscale characteristics of cordierite–mullite saggars. The 3D distribution of minerals in a 20×13×12 mm3 saggar sample is obtained. The results indicate that the direct dissolution of cordierite corrosion resistance reaction products is the primary damage mechanism of the saggar.

Suppressed O3–P3 phase transition of Cu/Fe/Mn-based layered oxides as cathode materials for high performance sodium-ion batteries

O3-type Cu/Fe/Mn-based layered oxides are regarded as promising cathode materials for sodium-ion batteries due to the abundance of elements in the Earth's crust and the imperative for large-scale energy storage. However, these materials still encounter some challenges, including low capacity and insufficient rate performance. In this study, Al-doped, cobalt-free, and nickel-free Na0.9Cu0.18Fe0.3Mn0.52-xAlxO2 (x = 0, 0.03, 0.05, 0.08) are successfully synthesized by using the solid-state method to introduce non-electrochemically active elements to stabilize the crystal structure and enhance the electrochemical performance. The impact of Al-doping is comprehensively analyzed by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), galvanostatic intermittent titration technique (GITT), and electrochemical impedance spectroscopy (EIS). Al-doping effectively enhances the diffusion coefficient of Na+, reduces the Jahn-Teller effect caused by Mn3+ and mitigates the transition from O3 to P3 phase. Finally, it stops the partial phase transitions from O3 to P3, which can be found in pristine oxide without Al-doping during charge-discharge cycling. Notably, the Na0.9Cu0.18Fe0.3Mn0.47Al0.05O2 electrode exhibits a reversible capacity of 123.89 mAh g−1 at 0.1 C, a capacity retention rate of 91.1 % after 200 cycles at 1 C, and a discharge capacity of 66.36 mAh g−1 at a high rate of 5 C.

Engineering interleaved large and small Na4MnV(PO4)3@NC microspheres cathode towards high performance sodium ion batteries

The booming consumption of energy storage devices spontaneously accelerates the urgent development of robust cathode materials for sodium-ion batteries (SIBs). In view of this, the sodium superionic conductor Na4MnV(PO4)3 (NMVP), with considerable energy density of 425 Wh kg−1, has become the focus in SIB research. Despite this, the performance of NMVP is substantially compromised by Jahn-Teller distortion of Mn3+ ions in conjunction with inherently limited electronic conductivity. In order to address this limitation, this study introduces a series of N-doped carbon (NC) coated NMVP materials with interleaved large and small microsphere morphology. Of particular note, the optimized NMVP-NC2 shows the most excellent performance, maintaining a capacity of 65.7 mAh g−1 at 5C over 500 cycles. A full cell configuration employing an NMVP-NC2 cathode and a commercial hard carbon (HC) anode manifests commendable circular stability with a capacity of 80.7 mAh g−1 underneath 100 cycles at 1C, with an impressive 95.3 % capacity preservation. This distinctive architecture imparts the materials with a high tap density and a relatively low surface area, which is beneficial to the industrial employment. In addition, density functional theory (DFT) calculations indicate that the NC regulation significantly narrows the NMVP's bandgap and facilitates electron transfer, thereby accelerating electron/ion transport kinetics. The NC coating approach combined with large-scale spray drying tactic in this work offers a clear strategy to industrialize NMVP cathode towards high-performance SIBs.