Unveiling the mechanism of sodium ion storage for needle-shaped ZnxCo3-xO4 nanosticks as anode materials

Zn Makes a Difference: Cubic ZnBi38O60 as a Durable and High-Rate Anode for Rechargeable Na-Ion Batteries

A stoichiometric cubic phase of zinc bismuth oxide ZnBi38O60 (ZBO) is introduced as an anode for rechargeable Na-ion batteries. ZBO is synthesized using a coprecipitation method and characterized by various physicochemical techniques. Pristine ZBO shows a high cyclability in an ether-based electrolyte due to the formation of a robust interphase coupled with high Na+ conductivity. Fast charge-transfer kinetics and high chemical compatibility between the electrolyte and electrode result in a high reversible stable capacity of ∼300 mA h/g at 100 mA/g and ∼180 mA h/g at 1000 mA/g for the as-synthesized ZBO. Using in situ diffraction (XRD) experiments, both conversion and alloying reactions are found to be responsible for the observed good performance. A robust, multilayered SEI composed of an inner bismuth-rich inorganic layer and an outer polyether layer with high ionic conductivity is observed using X-ray photoelectron spectroscopy analysis. The battery characteristics are found to be superior to the individual binary oxides, Bi2O3 and ZnO, thus bringing out the advantages of the addition of zinc and the ternary system studied. Preliminary full cell studies with the ZBO anode and Na3V2(PO4)3 cathode show good performance with high energy density and stability. The present investigations reveal a great potential for the anode, ZBO, comprising earth-abundant elements, and will likely lead to an alternate anode material for rechargeable batteries.

Progress and Prospect of Bimetallic Oxides for Sodium-Ion Batteries: Synthesis, Mechanism, and Optimization Strategy

Sodium-ion batteries (SIBs) are considered as an alternative to and even replacement of lithium-ion batteries in the near future in order to address the energy crisis and scarcity of lithium resources due to the wide distribution and abundance of sodium resources on the earth. The exploration and development of high-performance anode materials are critical to the practical applications of advanced SIBs. Among various anode materials, bimetallic oxides (BMOs) have attracted special research attention because of their abundance, easy access, rich redox reactions, enhanced capacity and satisfactory cycling stability. Although many BMO anode materials have been reported as anode materials in SIBs, very limited studies summarized the progress and prospect of BMOs in practical applications of SIBs. In this review, recent progress and challenges of BMO anode materials for SIBs have been comprehensively summarized and discussed. First, the preparation methods and sodium storage mechanisms of BMOs are discussed. Then, the challenges, optimization strategies, and sodium storage performance of BMO anode materials have been reviewed and summarized. Finally, the prospects and future research directions of BMOs in SIBs have been proposed. This review aims to provide insight into the efficient design and optimization of BMO anode materials for high-performance SIBs.

Enhanced sodium storage kinetics by volume regulation and surface engineering via rationally designed hierarchical porous FeP@C/rGO

Transition metal phosphides, such as iron phosphide (FeP), have been considered as promising anode candidates for high-performance sodium ion batteries (SIBs) owing to their high theoretical capacity. However, the development of FeP is limited by large volume change, low electrical conductivity and sluggish kinetics with sodium ions. Moreover, the sodium storage kinetics and dynamics behavior in FeP are still unclear. Herein, improved sodium storage ability of FeP is achieved by volume regulation and surface engineering via a rationally designed hierarchical porous FeP@C/rGO nanocomposite. This FeP@C/rGO nanocomposite exhibits excellent rate capability and long cycle life as the anode of SIBs. Specifically, the FeP@C/rGO nanocomposite delivers high specific capacities of 635.7 and 343.1 mA h g-1 at 20 and 2000 mA g-1, respectively, and stable cycling with 88.2% capacity retention after 1000 cycles. The kinetics and dynamics studies demonstrate that the superior performance is attributed to the rationally designed hierarchical porous FeP@C/rGO with a high capacitive contribution of 93.9% (at 2 mV s-1) and a small volume expansion of only 54.9% by in situ transmission electron microscopy (TEM) measurement. This work provides valuable insights into understanding the phase evolution of FeP during the sodiation/desodiation process for designing high-performance SIBs.