NASICON-type air-stable and all-climate cathode for sodium-ion batteries with low cost and high-power density

Building High Power Density of Sodium-Ion Batteries: Importance of Multidimensional Diffusion Pathways in Cathode Materials

Emerging sodium-ion batteries (SIBs) devices hold the promise to leapfrog over existing lithium-ion batteries technologies with respect to desirable power/energy densities and the abundant sodium sources on the earth. To this end, the discoveries on novel cathode materials with outstanding rate capabilities are being given high priority in the quest to achieve high power density SIBs devices, and the multi-dimensional Na⁺ migration pathways with low diffusion energy barriers are crucial. In light of this, the recent development of Prussian blue analogs and sodium superionic conductor (NASICON)-type materials with 3D Na⁺ diffusion pathways for building high power density NIBs are provided in this perspective. Ultimately, the future research directions to realize them for real applications are also discussed.

Hierarchically Porous MoS2-Carbon Hollow Rhomboids for Superior Performance of the Anode of Sodium-Ion Batteries

It is always challenging to fabricate two-dimensional transition-metal dichalcogenides into multiple hollow micro-/nanostructures with improved properties for various potential applications. Here, hierarchically porous MoS₂-C hollow rhomboids (MCHRs) have been creatively synthesized via a facile self-templated solvothermal approach. It has been clarified that the obtained MCHRs assembled beneath ultrathin γ-MnS and carbon cohybridized MoS₂ nanosheets under the structural direction of the MnMoO₄·0.49H₂O self-template. The prepared MCHR anode of sodium-ion batteries exhibited a reversible capacity of 506 mA h g^-1 at 0.1 A g^-1, ultrahigh rate capabilities up to 10 A g^-1 with 310 mA h g^-1, and exceptional stability over 3000 cycles. This study provides inspiration for the rational design of hierarchically porous hollow nanostructures with specific geometries as an excellent electrode material for outstanding performance energy storage equipment.

A Novel NASICON-Type Na4 MnCr(PO4 )3 Demonstrating the Energy Density Record of Phosphate Cathodes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have attracted incremental attention as a promising candidate for grid-scale energy-storage applications. To meet practical requirements, searching for new cathode materials with high energy density is of great importance. Herein, a novel Na superionic conductor (NASICON)-type Na₄ MnCr(PO₄ )₃ is developed as a high-energy cathode for SIBs. The Na₄ MnCr(PO₄ )₃ nanoparticles homogeneously embedded in a carbon matrix can present an extraordinary reversible capacity of 160.5 mA h g^-1 with three-electron reaction at ≈3.53 V during the Na⁺ extraction/insertion process, realizing an unprecedentedly high energy density of 566.5 Wh kg^-1 in the phosphate cathodes for SIBs. It is intriguing to reveal the underlying mechanism of the unique Mn²⁺ /Mn³⁺ , Mn³⁺ /Mn⁴⁺ , and Cr³⁺ /Cr⁴⁺ redox couples via X-ray absorption near-edge structure spectroscopy. The whole electrochemical reaction undergoes highly reversible single-phase and biphasic transitions with a moderate volume change of 7.7% through in situ X-ray diffraction and ex situ high-energy synchrotron X-ray diffraction. Combining density functional theory (DFT) calculations with the galvanostatic intermittent titration technique, the superior performance is ascribed to the low ionic-migration energy barrier and desirable Na-ion diffusion kinetics. The present work can offer a new insight into the design of multielectron-reaction cathode materials for SIBs.

Reversible structural evolution of sodium-rich rhombohedral Prussian blue for sodium-ion batteries

Iron-based Prussian blue analogs are promising low-cost and easily prepared cathode materials for sodium-ion batteries. Their materials quality and electrochemical performance are heavily reliant on the precipitation process. Here we report a controllable precipitation method to synthesize high-performance Prussian blue for sodium-ion storage. Characterization of the nucleation and evolution processes of the highly crystalline Prussian blue microcubes reveals a rhombohedral structure that exhibits high initial Coulombic efficiency, excellent rate performance, and cycling properties. The phase transitions in the as-obtained material are investigated by synchrotron in situ powder X-ray diffraction, which shows highly reversible structural transformations between rhombohedral, cubic, and tetragonal structures upon sodium-ion (de)intercalations. Moreover, the Prussian blue material from a large-scale synthesis process shows stable cycling performance in a pouch full cell over 1000 times. We believe that this work could pave the way for the real application of Prussian blue materials in sodium-ion batteries.

Here the authors deploy a scalable synthesis route to prepare sodium-rich Na_2−xFeFe(CN)₆ cathode materials for sodium-ion battery. The highly reversible structural evolution during cycling between rhombohedral, cubic and tetragonal phases is the key to enable the good performance.

Polyanion-type cathode materials for sodium-ion batteries

This review summarizes the recent progress and remaining challenges of polyanion-type cathodes, providing guidelines towards high-performance cathodes for sodium ion batteries.

Exploring the Role of Manganese on Structural, Transport, and Electrochemical Properties of NASICON-Na3Fe2-yMny(PO4)3-Cathode Materials for Na-Ion Batteries

Given the extensive efforts focused on protecting the environment, eco-friendly cathode materials are a prerequisite for the development of Na-ion battery technology. Such materials should contain abundant and inexpensive elements. In the paper, we present NASICON-Na₃Fe_2-yMn_y(PO₄)₃ (y = 0, 0.1, 0.2, 0.3, and 0.4) cathode materials, which meet these requirements. Na₃Fe_2-yMn_y(PO₄)₃ compounds were prepared via a solid-state reaction at 600 °C, which allowed to obtain powders with submicron particles. The presence of manganese in the iron sub-lattice inhibits phase transitions, which occurs at ∼95 and ∼145 °C in Na₃Fe₂(PO₄)₃, changing the monoclinic structure to rhombohedral and affecting the structural and transport properties. The chemical stability of Na₃Fe_2-yMn_y(PO₄)₃ was thus higher than that of Na₃Fe₂(PO₄)₃, and it also exhibited enhanced structural, transport, and electrochemical properties. The observed correlation between the chemical composition and electrochemical properties proved the ability to precisely tune the crystal structure of NASICONs, allowing cathode materials with more desirable properties to be designed.

Engineering 3D Well-Interconnected Na4MnV(PO4)3 Facilitates Ultrafast and Ultrastable Sodium Storage

Na₄MnV(PO₄)₃ (denoted as NMVP) has drawn increasing attention owing to the three-dimensional framework and high theoretical capacity. Nevertheless, the inherent low electronic conductivity of NMVP impedes the scale-up commercial applications. In this work, the feasibility to achieve ultrahigh-rate capability and long lifespan by in situ embedding the intertwined carbon nanotube (CNT) matrix into the bulk of Na₄MnV(PO₄)₃@C composites through a facile wet-chemical approach is reported. The elaborately prepared Na₄MnV(PO₄)₃@C@CNTs cathode delivers a discharge capacity of 109.9 mA h g^-1 at C/5 with an impressive rate capability of 68.9 mA h g^-1 at an ultrahigh current rate of 90 C as well as a fascinating cycling performance of 68.3% capacity retention at 40 C after 4000 cycles. The optimum design of the 3D well-interconnected NMVP permitting fast kinetics for transported Na⁺/e^- is beneficial to the excellent electrochemical performance, which is further studied by the galvanostatic intermittent titration technique, cyclic voltammetry, and electrochemical impedance spectra measurements. The pseudocapacitance contributions are also investigated. The research demonstrates that the dual-nanocarbon synergistically modified NMVP composite is expected to facilitate the commercialization of sodium-ion batteries.