Rechargeable Sodium-Ion Battery Based on Polyazaacene Analogue Anode

Construction of oxygen vacancies and heterostructure in VO2-x/NC with enhanced reversible capacity, accelerated redox kinetics, and stable cycling life for sodium ion storage

Developing anode materials with high reversible capacity, fast redox kinetics, and stable cycling life for Na⁺ storage remains a great challenge. Herein, the VO₂ nanobelts with oxygen vacancies supported on nitrogen-doped carbon nanosheets (VO_2-x/NC) were developed. Benefitting from the enhanced electrical conductivity, the accelerated kinetics, the increased active sites as well as the constructed 2D heterostructure, the VO_2-x/NC delivered extraordinary Na⁺ storage performance in half/full battery. Theoretical calculations (DFT) demonstrated that oxygen vacancies could regulate the adsorption ability for Na⁺, enhance electronic conductivity, as well as achieve rapid and reversible Na⁺ adsorption/desorption. The VO_2-x/NC exhibited high Na⁺ storage capacity of 270 mAh g^-1 at 0.2 A g^-1, and impressive cyclic stability with 258 mAh g^-1 after 1800 cycles at 10 A g^-1. The assembled sodium-ion hybrid capacitors (SIHCs) could achieve maximum energy density/power output of 122 Wh kg^-1/9985 W kg^-1, ultralong cycling life with 88.4% capacity retention after 25,000 cycles at 2 A g^-1, and practical applications (55 LEDs could be actuated for 10 min), promising to be utilized in a practicable Na⁺ storage.

Recent Progress in Rechargeable Sodium Metal Batteries: A Review

Sodium metal batteries (SMBs) have been widely studied owing to their relatively high energy density and abundant resources. However, they still need systematic improvement to fulfill the harsh operating conditions for their commercialization. In this review, we summarize the recent progress in SMBs in terms of sodium anode modification, electrolyte exploration, and cathode design. Firstly, we give an overview of the current challenges facing Na metal anodes and the corresponding solutions. Then, the traditional liquid electrolytes and the prospective solid electrolytes for SMBs are summarized. In addition, insertion- and conversion-type cathode materials are introduced. Finally, an outlook for the future of practical SMBs is provided.

Thermodynamic Transformation of Crystalline Organic Hybrid Iron Selenide to FexSey@CN Microrods for Sodium Ion Storage

Carbon-coated metal chalcogenide composites have been demonstrated as one type of promising anode material for sodium-ion batteries (SIBs). However, combining carbon materials with micronanoparticles of metal chalcogenide always involve complicated processes, such as polymer coating, carbonization, and sulfidation/selenization. To address this issue, herein, we reported a series of carbon-coated FexSey@CN (FexSey = FeSe2, Fe3Se4, Fe7Se8) composites prepared via the thermodynamic transformation of a crystalline organic hybrid iron selenide [Fe(phen)2](Se4) (phen = 1,10-phenanthroline). By pyrolyzing the bulk crystals of [Fe(phen)2](Se4) at different temperatures, FexSey microrods were formed in situ, where the nitrogen-doped carbon layers were coated on the surface of the microrods. Moreover, all the as-prepared FexSey@CN composites exhibited excellent sodium-ion storage capabilities as anode materials in SIBs. This work proves that crystalline organic hybrid metal chalcogenides can be used as a novel material system for the in situ formation of carbon-coated metal chalcogenide composites, which could have great potential in the application of electrochemical energy storage.

Double-layer Composite Gel Polymer Electrolyte for Organic Sodium-metal Batteries

Organic cathode materials have the advantages of abundant raw materials, high theoretical specific capacity, controllable structure and easy recycling. Pyrene-4,5,9,10-tetraone (PTO), as one of the typical organic cathode materials, achieves efficient storage and release of Na + . However, its good solubility in traditional organic liquid electrolytes is detrimental to the cyclic stability of batteries. To address this issue, the double-layer composite gel polymer electrolyte (DLCGPE) consisting of poly (ionic liquid) gel polymer electrolyte and plastic crystal electrolyte was developed and applied to organic sodium-metal batteries. This as-prepared DLCGPE displays an ionic conductivity of 2.17×10 -4 S cm -1 and an electrochemical window of 4.8 V. The as-fabricated sodium-symmetric batteries maintain interfacial stability after 500 h of cycling. Furthermore, the PTO/Na batteries could also retain a specific capacity of 201 mAh g -1 after 300 cycles, confirming that DLCGPE achieves the purpose of inhibiting PTO dissolution and maintaining batteries stability. This work broadens the application of asymmetric electrolytes in organic secondary battery.