Cathode For Sodium-ion Batteries Research Articles

Pristine Metal‐Organic Frameworks for Sodium‐Ion Batteries: Past, Present, and Future

AbstractOwing to their adjustable redox‐active sites, designable structures high porosity, and fully activated organic ligands, pristine metal‐organic frameworks (MOFs) have been widely utilized as advanced electrode materials (i. e., both anodes and cathodes) for sodium‐ion batteries (SIBs) to satisfied the insertion/extraction larger size and mass of Na+ cations, achieving significant progresses with excellent electrochemical performance in electrochemical energy storage devices. Here, the recent advances on pristine MOFs as anodes and cathodes for SIBs are summarized. A thorough investigation delves into the detailed characteristics, energy storage mechanisms, and electrochemical performance of diverse pristine MOFs for SIBs are also clarified. Furthermore, the outlooks on pristine MOF electrodes in SIBs are also provided.

Distinct electrochemical behavior of P3 and P2 polytypes of Mn/Ni-based Na-ion battery cathode

A layered sodium-ion battery cathode Na34Mn1116Ni316Al216O2 (NMNA) prepared in P3 and P2 polytype structures by varying the calcination temperature is systematically investigated for its structural and electrochemical behavior. P3-phase prepared at 650 °C delivered a higher initial capacity of 164 mAh/g (∼148 mAh/g for P2-phase calcined at 850 °C) at 0.1C. In contrast, the P2-phase sample exhibited better rate performance (87 mAh/g vs. 70 mAh/g for P3-phase at 4C) and capacity retention of ∼47 % after 200 cycles (only ∼26 % for P2-phase). Electrochemical impedance measurements before and after cycling confirmed that the increase in charge transfer resistance is responsible for the poor rate performance of the P3 phase.

A multicationic-substituted configurational entropy-enabled NASICON cathode for high-power sodium-ion batteries

Na-superionic-conductor (NASICON)-type Na3V2(PO4)3 is considered as one of the potential cathodes for sodium-ion batteries (SIBs), but its inherent low electronic conductivity and non-adjustable voltage plateau is an urgent issue hindrance to its practical application. Hereof, the concept of multicationic-substituted high-entropy doping is innovatively utilized to modify the fine structure within crystals, enhance electronic conductivity, and achieve excellent local diffusion kinetics and high redox activity according to theoretical calculations. The carbon-free Na3V1.8(CrMnFeZnAl)0.2(PO4)3 (HE-NVP-0.2) cathode exhibits a maximum specific capacity of 119.8 mA h g−1, achieved through V3+/V4+/V5+ redox reactions, while maintaining an impressive capacity retention rate of 80 % after 3000 cycles at 10 C. Moreover, the in-situ X-ray diffraction (XRD) analysis reveals that the incorporation of multi-(high entropy) elements induces a stable transition state, facilitating rapid phase transitions. Combined with in-situ digital image correlation (DIC), reversible structural evolution has been verified at both micro and macro scales. More competitively, coupling with a hard carbon (HC) anode, the HE-NVP-0.2//HC full cells exhibit exceptional energy density/power density characteristics while simultaneously maintaining excellent high-rate performance and prolonged cycle life (2000 stable cycles at 50 C). The regulation of configurational entropy enables the realization of an intermediate phase in the equilibrium state and makes the unlikely potential regulation possible, presenting innovative approaches to expedite the commercialization of high-power SIBs.

Preparation high-performance cathode of vacancy-free Prussian blue analogues for sodium ion batteries by directional capture of free Mn-ion

To address the issue of poor cycling performance and capacity of Mn-based Prussian Blue analogues (PBAs) as sodium ion battery cathodes due to the solubility of Mn ions, this study utilizes the strong chelating property of EDTA2− with Mn ions to hydrothermally modify the sodium-rich monoclinic Na1.75Mn[Fe(CN)6]0.94·2.25H2O synthesized under high salt conditions, in order to enhance its capacity and stability. The modified Na1.93Mn[Fe(CN)6]•2·.38H2O exhibits a discharge capacity of 156.16 mAh/g at 10 mA g−1 (91.86 % of the theoretical capacity), it still retains the highest discharge capacity (70.23 mAh/g) after 500 cycles at 100 mA g−1. Based on experimental analysis, the improvement in the electrochemical performance of PBAs was attributed to three main factors: (1) enhanced Na content; (2) suppression of defects; and (3) improved crystal structure.

Tailoring of High-Valent Sn-Doped Porous Na3V2(PO4)3/C Nanoarchitechtonics: An Ultra High-Rate Cathode for Sodium-Ion Batteries.

NASICON structured Na3V2(PO4)3 (NVP) has captured enormous attention as a potential cathode for next-generation sodium-ion batteries (SIBs), owing to its sturdy crystal structure and high theoretical capacity. Nonetheless, its poor intrinsic electronic conductivity has led to inferior electrochemical performance in terms of rate capability and long cycling performance. To address this problem, a combined strategy is adopted, such as (1) carbon coating and (2) high valent Sn4+ ion doping in the lattice site of vanadium in the NVP cathode. Carbon coating can effectively enhance the surface electronic conductivity, wherein high-valent Sn4+ improves the bulk intrinsic electronic conductivity of the materials. Moreover, Sn is a well-known alloying/dealloying type anode for SIBs; thus, doping of such metal in cathode materials will assume the role of structure stabilizing pillars and establishing high-performing cathode materials. Herein, Na3V2-xSnx(PO4)3/C (denoted as Sn(x)-NVP/C, where x = 0.00, 0.03, 0.05, 0.07, 0.1) were synthesized via sol-gel route, followed by calcination at 800 °C. XRD, Raman, XPS, and electron microscopy data confirmed the high purity of the synthesized cathode. The optimized Sn(0.07)-NVP/C exhibited excellent electrochemical performance in terms of high rate capability and long cycling performance, a high appreciable capacity of 98 mAh g-1 with capacity retention of 85% after 500 cycles. Similarly, at a high current of 20C, it is still able to deliver a stable capacity of 76 mAh g-1 with 85% capacity retention after 3000 cycles. The rate capability study indicates the high current tolerance of Sn(0.07)-NVP/C up to 70 C with a capacity delivery of 55 mAh g-1. It is worth mentioning that CV and EIS analysis for Sn(0.07)-NVP/C cathode displayed minimum voltage polarization and enhanced diffusion coefficient. Moreover, DFT calculation also proved that the electronic and ionic conductivity of NVP is promoted by Sn doping. Hence, the present results demonstrated that Sn(0.07)-NVP/C is considered a promising cathode for sodium-ion battery application.

Revealing the Nature of Binary-Phase on Structural Stability of Sodium Layered Oxide Cathodes.

The emergence of layered sodium transition metal oxides featuring a multiphase structure presents a promising approach for cathode materials in sodium-ion batteries, showcasing notably improved energy storage capacity. However, the advancement of cathodes with multiphase structures faces obstacles due to the limited understanding of the integrated structural effects. Herein, the integrated structural effects by an in-depth structure-chemistry analysis in the developed layered cathode system NaxCu0.1Co0.1Ni0.25Mn0.4Ti0.15O2 with purposely designed P2/O3 phase integration, are comprehended. The results affirm that integrated phase ratio plays a pivotal role in electrochemical/structural stability, particularly at high voltage and with the incorporation of anionic redox. In contrast to previous reports advocating solely for the enhanced electrochemical performance in biphasic structures, it is demonstrated that an inappropriate composite structure is more destructive than a single-phase design. The in situ X-ray diffraction results, coupled with density functional theory computations further confirm that the biphasic structure with P2:O3 = 4:6 shows suppressed irreversible phase transition at high desodiated states and thus exhibits optimized electrochemical performance. These fundamental discoveries provide clues to the design of high-performance layered oxide cathodes for next-generation SIBs.

Suppressing the Jahn–Teller effect in Mn-based Prussian blue analogues by linear (N[dbnd]O) anions

Manganese-based Prussian blue analogues (PBAs) have been touted as a promising cathode material for sodium-ion batteries (SIBs) due to their low cost, long cycle life and high energy density. However, manganese-based PBAs perform poorly during cycling due to the Jahn-Teller effect. In this study, highly stable manganese nitrosylpentacyanoferrate (Mn[Fe(CN)5NO]) particles were synthesized using a simple hydrothermal method. The presence of nitroso group breaks the symmetry of the crystals to some extent, which is favorable to reduce the Jahn-Teller effect. Through experiments and DFT calculations, we confirm that the presence of linear (NO) anions reduces the lattice volume fluctuations of the samples during charging and discharging, thus contributing to the mitigation of the Jahn-Teller effect. The electrochemical properties of Mn[Fe(CN)5NO] were significantly improved compared to manganese hexacyanoferrate (MnFe[CN]6). Mn[Fe(CN)5NO] exhibited excellent sodium storage performance with an initial discharge capacity as high as 144.5 mAh/g at 20 mA g-1and capacity retention as high as 82.1 % after 400 cycles at 100 mA g−1. This Mn[Fe(CN)5NO] sample provides a promising cathode for sodium-ion batteries in large-scale energy storage systems.

Stabilizing NASICON-type Na4MnCr(PO4)3 by Ti-substitution toward a high-voltage cathode material for sodium ion batteries

The sodium superionic conductor Na4MnCr(PO4)3 gains increasing attention owing to its three-dimensional structure and the three-electron reaction. However, rapid structure degradation during cycling is the major challenge for its practical application. Herein, Ti4+ is utilized to replace a portion of Mn2+ in Na4MnCr(PO4)3. The low redox voltage and d0 electronic configuration of the Ti4+ ions are helpful to suppress the structure alteration and improve electronic conduction. Consequently, the as-prepared Na3.4Mn0.7Ti0.3Cr(PO4)3/C cathode exhibits a remarkable good 91.0% capacity retention after 500 cycles at 10C rate, with exceptional rate capacities of 99.5 mAh g−1 and 81.0 mAh g−1 at 5C and 10C rate, respectively. Furthermore, based on ≈2.86-electron reactions involving Mn2+/Mn3+ (3.5 V), Mn3+/Mn4+ (4.1 V), Cr3+/Cr4+ (4.3 V), and Ti3+/Ti4+ (2.1 V), the material can provide an energy density of approximately 541.6 Wh kg−1, slightly surpassing that of Na4MnCr(PO4)3. Ex-situ XRD investigation further elucidates that throughout the entire charge–discharge process, the Ti-substituted material experiences highly reversible solid-solution and two-phase reactions. Additionally, Ti substitution can greatly promote the interfacial charge transfer of the material and suppress the decomposition of the electrolyte during cycling. This work might open a new insight for designing sodium-ion battery cathode materials with good cycling stability and high energy density.

Anchored VN Quantum Dots Boosting High Capacity and Cycle Durability of Na3V2(PO4)3@NC Cathode for Aqueous Zinc-Ion Battery and Organic Sodium-Ion Battery.

Na3V2(PO4)3 is a promising high-voltage cathode for aqueous zinc-ion batteries (ZIBs) and organic sodium-ion batteries (SIBs). However, the poor rate capability, specific capacity, and cycling stability severely hamper it from further development. In this work, Na3V2(PO4)3 (NVP) with vanadium nitride (VN) quantum dots encapsulated by nitrogen-doped carbon (NC) nanoflowers (NVP/VN@NC) are manufactured as cathode using in situ nitridation, carbon coating, and structural adjustment. The outer NC layer increases the higher electronic conductivity of NVP. Furthermore, VN quantum dots with high theoretical capacity not only improve the specific capacity of pristine NVP, but also serve as abundant "pins" between NVP and NC to strengthen the stability of NVP/VN@NC heterostructure. For Zn-ion storage, these essential characteristics allow NVP/VN@NC to attain a high reversible capacity of 135.4mAhg-1 at 0.1Ag-1, and a capacity retention of 91% after 2000 cycles at 5Ag-1. Meanwhile, NVP/VN@NC also demonstrates to be a stable cathode material for SIBs, which can reach a high reversible capacity of 124.5mAhg-1 at 0.1Ag-1, and maintain 92% of initial capacity after 11000 cycles at 5Ag-1. This work presents a feasible path to create innovative high-voltage cathodes with excellent reaction kinetics and structural stability.

First-principles study of high-entropy sulfides and their alkali metal-doped modification as cathode material for sodium-ion batteries.

High-entropy materials (HEMs) have been explored as high-capacity cathode materials for sodium-ion batteries (SIBs) due to their excellent structural stability and abundant metal redox sites. Among them, high-entropy sulfides (HESs) have greater potential and more extensive research than high-entropy oxides, as they exhibit higher charging voltage and theoretical capacity as cathodes. Furthermore, alkali metal doping of HESs can further enhance their performance and broaden their application fields. Inspired by the cocktail effect of HEMs, we performed the first theoretical calculation of the properties of Na(MnFeCoNi)1/2S and its Li-doped derivative, Na7/8Li1/8(MnFeCoNi)1/2S, to understand their potential as SIB cathode materials. Using density functional theory based on first principles, we investigated the structure and electronic characteristics of Na(MnFeCoNi)1/2S and Na7/8Li1/8(MnFeCoNi)1/2S, and calculated their theoretical voltage and capacity, respectively. Compared with Na(MnFeCoNi)1/2S, Na7/8Li1/8(MnFeCoNi)1/2S showed better electronic performance in reducing the band gap and increasing the density of states, ultimately providing a specific capacity of 160.3 mAh·g-1 and a charging voltage of 4.85 V in sodium-ion storage. Moreover, Na7/8Li1/8(MnFeCoNi)1/2S exhibited remarkable structural stability throughout the sodium-ion deintercalation process, thus it can be reasonably concluded that Na7/8Li1/8(MnFeCoNi)1/2S can serve as an excellent cathode material for future SIB applications.

A High-Entropy Approach to Activate the Oxygen Redox Activity and Suppress the Phase Transition of P2-Type Layered Cathode for Sodium-Ion Batteries

A High-Entropy Approach to Activate the Oxygen Redox Activity and Suppress the Phase Transition of P2-Type Layered Cathode for Sodium-Ion Batteries

A Comprehensive Review on Strategies for Enhancing the Performance of Polyanionic-Based Sodium-Ion Battery Cathodes.

The significant consumption of fossil fuels and the increasing pollution have spurred the development of energy-storage devices like batteries. Due to their high cost and limited resources, widely used lithium-ion batteries have become unsuitable for large-scale energy production. Sodium is considered to be one of the most promising substitutes for lithium due to its wide availability and similar physiochemical properties. Designing a suitable cathode material for sodium-ion batteries is essential, as the overall electrochemical performance and the cost of battery depend on the cathode material. Among different types of cathode materials, polyanionic material has emerged as a great option due to its higher redox potential, stable crystal structure, and open three-dimensional framework. However, the poor electronic and ionic conductivity limits their applicability. This review briefly discusses the strategies to deal with the challenges of transition-metal oxides and Prussian blue analogue, recent developments in polyanionic compounds, and strategies to improve electrochemical performance of polyanionic material by nanostructuring, surface coating, morphology control, and heteroatom doping, which is expected to accelerate the future design of sodium-ion battery cathodes.

Mesoporous hollow Fe4[Fe(CN)6)]3 hierarchical nanocrystal architecture for advanced sodium-ion batteries

Prussian blue (PB) has been broadly recognized as promising cathode materials for sodium-ion batteries (SIBs) due to its large interstitial space and robust frame structure, whereas their applications are impeded by unsatisfied long-term cyclability and poor rate capability due to its inherent lattice defects. Herein, we report to fabricate the mesoporous hollow Fe4(Fe(CN)6)3 (one kind of PB) hierarchical nanocrystal architecture by the hydrothermal crystallization and HCl etching of the mesoporous precursor Fe4[Fe(CN)6]3 cubic particles, leading to high crystallinity and large specific surface area. The resultant Fe4[Fe(CN)6]3 cathode for SIBs exhibits a good reversibility and cycling stability with a capacity retention of 75.6 % at 0.5 C after 200 cycles as well as superb rate capability featuring a stable discharge specific capacity of 30.2 mAh g−1 at as high as 10 C, demonstrating the fast kinetics and low polarization of electrochemical reaction, which might be ascribed to the unique architecture and high crystallinity. This offers a new route to designing PB cathode of for SIBs with high rate capabilities.

Solid-Solution Reaction and Ultrasmall Volume Change in High-Entropy P2-type Layered Oxide Cathode for All-Climate Sodium-Ion Batteries

Solid-Solution Reaction and Ultrasmall Volume Change in High-Entropy P2-type Layered Oxide Cathode for All-Climate Sodium-Ion Batteries

Manipulating Local Chemistry and Coherent Structures for High-Rate and Long-Life Sodium-Ion Battery Cathodes.

Layered sodium transition-metal (TM) oxides generally suffer from severe capacity decay and poor rate performance during cycling, especially at a high state of charge (SoC). Herein, an insight into failure mechanisms within high-voltage layered cathodes is unveiled, while a two-in-one tactic of charge localization and coherent structures is devised to improve structural integrity and Na+ transport kinetics, elucidated by density functional theory calculations. Elevated Jahn-Teller [Mn3+O6] concentration on the particle surface during sodiation, coupled with intense interlayer repulsion and adverse oxygen instability, leads to irreversible damage to the near-surface structure, as demonstrated by X-ray absorption spectroscopy and in situ characterization techniques. It is further validated that the structural skeleton is substantially strengthened through the electronic structure modulation surrounding oxygen. Furthermore, optimized Na+ diffusion is effectively attainable via regulating intergrown structures, successfully achieved by the Zn2+ inducer. Greatly, good redox reversibility with an initial Coulombic efficiency of 92.6%, impressive rate capability (86.5 mAh g-1 with 70.4% retention at 10C), and enhanced cycling stability (71.6% retention after 300 cycles at 5C) are exhibited in the P2/O3 biphasic cathode. It is believed that a profound comprehension of layered oxides will herald fresh perspectives to develop high-voltage cathode materials for sodium-ion batteries.

Mixed polyanionic NaFe1.6V0.4(PO4)(SO4)2@CNT cathode for sodium-ion batteries: Electrochemical diffusion kinetics and distribution of relaxation time analysis at different temperatures

We report the electrochemical sodium-ion kinetics and distribution of relaxation time (DRT) analysis of a newly designed mixed polyanionic NaFe1.6V0.4(PO4)(SO4)2@CNT composite as a cathode. The specific capacity of 104 mAhg−1 is observed at 0.1 C with the average working voltage of ∼3 V. Intriguingly, a remarkable rate capability and reversibility are demonstrated up to very high current rate of 25 C. The long cycling test up to 10 C shows high capacity retention even after 2000 cycles. The detailed analysis of galvanostatic intermittent titration technique (GITT) and cyclic voltammetry (CV) data reveal the diffusion coefficient of 10−8–10−11 cm2s−1. We find excellent stability in the thermal testing between 25–55 °C temperatures and 80% capacity retention up to 100 cycles at 5 C. Further, we analyze the individual electrochemical processes in the time domain using the novel DRT technique at different temperatures. The ex-situ investigation shows the stable and reversible structure, morphology and electronic states of the long cycled cathode material. More importantly, we demonstrate relatively high specific energy of ≈155 Wh kg−1 (considering the total active material loading of both the electrodes) at 0.2 C for full cell battery having excellent rate capability up to 10 C and long cyclic stability at 1 C.

Air Corrosion of Layered Cathode Materials for Sodium-Ion Batteries: Cation Mixing and a Practical Suppression Strategy.

Layered oxide cathodes of sodium-ion batteries (SIBs) are considered promising candidates due to their fascinating high capacity, good cyclability, and environmental friendliness. However, the air sensitivity of layered SIB cathodes causes high electrode manufacturing costs and performance deterioration, hampering their practical application. Herein, a commercial O3-type layered Na(Ni1/3Fe1/3Mn1/3)O2 (NNFM) material is adopted to investigate the air corrosive problem and the suppression strategy. We reveal that once the layered material comes in contact with ambient air, cations migrate from transition metal (TM) layers to sodium layers at the near surface, although Na+ and TM ions show quite different ion radii. Experimental results and theoretical calculations show that more Ni/Na disorder occurs in the air-exposed O3-NNFM materials, owing to a lower Ni migration energy barrier. The cation mixing results in detrimental structural distortion, along with the formation of residual alkali species on the surface, leading to high impedance for Na+ diffusion during charge/discharge. To tackle this problem, an ultrathin and uniform hydrophobic molecular layer of perfluorodecyl trimethoxysilane is assembled on the O3-NNFM surface, which significantly suppresses unfavorable chemistry and structure degradation during air storage. The in-depth understanding of the structural degradation mechanism and suppression strategy presented in this work can facilitate high-energy cathode manufacturing from the perspective of future practical implementation and commercialization.

Na3.8MnV0.8Zr0.2(PO4)3/C/rGO composite cathode for sodium-ion battery with enhanced cycling stability and rate capability

Na3.8MnV0.8Zr0.2(PO4)3/C/rGO composite cathode for sodium-ion battery with enhanced cycling stability and rate capability

A Feasible Dual Modification Strategy of Internal Anion Redox Chemistry and Surface Engineering on P2 Layer-Structured Cathodes in Sodium-Ion Batteries.

Boosting the anion redox reaction opens up a possibility of further capacity enhancement on transition-metal-ion redox-only layer-structured cathodes for sodium-ion batteries. To mitigate the deteriorating impact on the internal and surface structure of the cathode caused by the inevitable increase in the operation voltage, probing a solution to promote the bulk-phase crystal structure stability and surface chemistry environment to further facilitate the electrochemical performance enhancement is a key issue. A dual modification strategy of establishing an anion redox hybrid activation trigger agent inside the crystal structure in combination with surface oxide coating is successfully developed. P2-type layer structure cathode materials with Zn/Li (Na-O-Zn@Na-O-Li) anion redox hybrid triggers and a ZnO coating layer possess superior capacity and cycle performance, along with outstanding structural stability, decreased Mn-ion dissolution effect, and less crystal particle cracking during the cycling process. This study represents a facile modification solution to perform structure optimization and property enhancement toward high-performance layered structure cathode materials with anion redox features in sodium-ion batteries.

Tuning Electronegativity‐Difference Configuration to Construct Non‐Bonded O 2p Orbitals for Reversible Anionic Redox in O3‐Type Cathode

AbstractHow to tune the activity and reversibility of oxygen anion redox (OAR) is a critical issue for O3‐type sodium‐ion battery (SIB) cathodes. Herein, the key role of electronegativity‐difference configuration on the activation of OAR is find out, and further tune electronegativity‐difference configuration with La incorporation to construct non‐bonded O 2p orbitals and achieve the reversible anionic redox in O3‐type NaMn1/3Fe1/3Ni1/3O2. Owing to the special extranuclear electronic structure of La3+ [Xe], the La electron cloud is difficult to be disturbed by the O electron cloud, and some O electrons do not participate in the formation of ionic bonds, thus retaining the non‐bonded electrons of O 2p and activating OAR. Moreover, La3+ doping also decreases the Coulomb force between Na+ and O2− favoring Na+ migration as well as strengthening the La─O bonds inhibiting the irreversible phase transition. La2O3 coating layer also plays a role on inhibiting the reaction between molecular oxygen and the electrolyte, and making OAR reversible. After modification, the cycling stability is significantly improved (86.9% vs 27.3%@2C@200cycles; 90.8% vs 52.9%@5C@300 cycles). This study presents some insights on OAR activation mechanism and offers a facile strategy to improve the activity and reversibility of OAR for designing high performance SIBs cathodes.