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1. Concentration-Gradient Prussian Blue Cathodes for Na-Ion Batteries

   Hu P., Peng W. (January 2020, ACS energy letters)

   A concentration-gradient composition is proposed as an effective approach to solve the mechanical degradation and improve the electrochemical cyclability for cathodes of sodium-ion batteries. Concentration-gradient shell NaxNiyMn1-yFe(CN)6·nH2O, in which the Ni content gradually increases from the interior to the particle surface, is synthesized by a facile co-precipitation process. The as-obtained cathode exhibits an improved electrochemical performance compared to homogeneous NaxMnFe(CN)6·nH2O, delivering a high reversible specific capacity of 110 mA h g-1 at 0.2 C and outstanding cycling stability (93% retention after 1000 cycles at 5 C). The improvement of electrochemical performance can be attributed to its robust microstructure that effectively alleviates the electrochemically induced stresses and accumulated damage during sodiation/desodiation and thus prevents the initiation of fracture in the particles upon long term cycling. These findings render a prospective strategy to develop high-performance electrode materials for sodium-ion batteries. 

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2. Biomimetic composite architecture achieves ultrahigh rate capability and cycling life of sodium ion battery cathodes

   https://doi.org/10.1063/5.0020805  

   Shin, Kang_Ho; Park, Sul_Ki; Nakhanivej, Puritut; Wang, Yixian; Liu, Pengcheng; Bak, Seong-Min; Choi, Min_Sung; Mitlin, David; Park, Ho_Seok (December 2020, Applied Physics Reviews)

   Sodium ion batteries are an emerging candidate to replace lithium ion batteries in large-scale electrical energy storage systems due to the abundance and widespread distribution of sodium. Despite the growing interest, the development of high-performance sodium cathode materials remains a challenge. In particular, polyanionic compounds are considered as a strong cathode candidate owing to their better cycling stability, a flatter voltage profile, and stronger thermal stability compared to other cathode materials. Here, we report the rational design of a biomimetic bone-inspired polyanionic Na3V2(PO4)3-reduced graphene oxide composite (BI-NVP) cathode that achieves ultrahigh rate charging and ultralong cycling life in a sodium ion battery. At a charging rate of 1 C, BI-NVP delivers 97% of its theoretical capacity and is able to retain a voltage plateau even at the ultra-high rate of 200 C. It also shows long cycling life with capacity retention of 91% after 10 000 cycles at 50 C. The sodium ion battery cells with a BI-NVP cathode and Na metal anode were able to deliver a maximum specific energy of 350 W h kg−1 and maximum specific power of 154 kW kg−1. In situ and postmortem analyses of cycled BI-NVP (including by Raman and XRD spectra) HRTEM, and STEM-EELS, indicate highly reversible dilation–contraction, negligible electrode pulverization, and a stable NVP-reduced graphene oxide layer interface. The results presented here provide a rational and biomimetic material design for the electrode architecture for ultrahigh power and ultralong cyclability of the sodium ion battery full cells when paired with a sodium metal anode. 

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3. Electrochemical and Degradation Studies on One-Dimensional Tunneled Sodium Zirconogallate (NZGO) + Yttria-Stabilized Zirconia (YSZ) Composite, Mixed Sodium and Oxygen Ion Conductor

   https://doi.org/10.1149/1945-7111/ac9ee2  

   Elahi, Pooya; Horsley, Jude; Sparks, Taylor D. (November 2022, Journal of The Electrochemical Society)

   In recent years, multi-phase materials capable of multi-ion transport have emerged as attractive candidates for a variety of electrochemical devices. Here, we provide experimental results for fabricating a composite electrolyte made up of a one-dimensional fast sodium-ion conductor, sodium zirconogallate, and an oxygen-ion conductor, yttria-stabilized zirconia. The composite is synthesized through a vapor phase conversion mechanism, and the kinetics of this process are discussed in detail. The samples are characterized using diffraction, electron microscopy, and electrochemical impedance spectroscopy techniques. Samples with a finer grain structure exhibit higher kinetic rates due to larger three-phase boundaries (TPBs) per unit area. The total conductivity is fitted to an Arrhenius type equation with activation energies ranging from 0.23 eV at temperatures below 550 ° C to 1.07 eV above 550 ° C . The electrochemical performance of multi-phase multi-species, mixed Na + and O 2 − conductor, is tested under both oxygen chemical potential gradient as well as sodium chemical potential gradient are discussed using the Goldman-Hodgkin-Kats (GHK) and the Nernst equation. 

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4. Hard Carbon Derived from Avocado Peels as a High-Capacity, Fast Na ⁺ Diffusion Anode Material for Sodium-Ion Batteries

   https://doi.org/10.1149/2754-2734/ac8aaf  

   Genier, Francielli Silva; Pathreeker, Shreyas; Schuarca, Robson Luis; Islam, Mohammad; Hosein, Ian Dean (August 2022, ECS Advances)

   Deriving battery grade materials from natural sources is a key element to establishing sustainable energy storage technologies. In this work, we present the use of avocado peels as a sustainable source for conversion into hard carbon-based anodes for sodium ion batteries. The avocado peels are simply washed and dried then proceeded to a high temperature conversion step. Materials characterization reveals conversion of the avocado peels in high purity, highly porous hard carbon powders. When prepared as anode materials they show to the capability to reversibly store and release sodium ions. The hard carbon-based electrodes exhibit excellent cycling performance, namely, a reversible capacity of 352.55 mAh g⁻¹at 0.05 A g⁻¹, rate capability up to 86 mAh g⁻¹at 3500 mA g⁻¹, capacity retention of >90%, and 99.9% coulombic efficiencies after 500 cycles. Cyclic voltammetry studies indicated that the storage process was diffusion-limited, with diffusion coefficient of 8.62 × 10⁻⁸cm²s⁻¹. This study demonstrates avocado derived hard carbon as a sustainable source that can provide excellent electrochemical and battery performance as anodes in sodium ion batteries. 

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5. Computational Studies of Electrode Materials in Sodium‐Ion Batteries

   https://doi.org/10.1002/aenm.201702998  

   Bai, Qiang; Yang, Lufeng; Chen, Hailong; Mo, Yifei (March 2018, Advanced Energy Materials)

   Abstract Sodium‐ion batteries have attracted extensive interest as a promising solution for large‐scale electrochemical energy storage, owing to their low cost, materials abundance, good reversibility, and decent energy density. For sodium‐ion batteries to achieve comparable performance to current lithium‐ion batteries, significant improvements are still required in cathode, anode, and electrolyte materials. Understanding the functioning and degradation mechanisms of the materials is essential. Computational techniques have been widely applied in tandem with experimental investigations to provide crucial fundamental insights into electrode materials and to facilitate the development of materials for sodium‐ion batteries. Herein, the authors review computational studies on electrode materials in sodium‐ion batteries. The authors summarize the current state‐of‐the‐art computational techniques and their applications in investigating the structure, ordering, diffusion, and phase transformation in cathode and anode materials for sodium‐ion batteries. The unique capability and the obtained knowledge of computational studies as well as the perspectives for sodium‐ion battery materials are discussed in this review. 

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