Self-assembled nickel-cobalt oxide microspheres from rods with enhanced electrochemical performance for sodium ion battery

N-doped carbon encapsulated CoMoO4 nanorods as long-cycle life anode for sodium-ion batteries

Volume expansion and poor conductivity result in poor cyclability and low rate capability, which are the major challenges of transition-metal oxide as anode materials for sodium-ion batteries (SIBs). Herein, N-doped carbon encapsulated CoMoO₄ (CoMoO₄@NC) nanorods are developed as excellent anode materials for SIBs with long-cycle life. The N-doped carbon shells serve as buffer to accommodate severe volume changes during sodiation/desodiation, and at the same time improve electronic conductivity and activate surface sites of CoMoO₄. The optimized composite presents rapid reaction kinetics and excellent cycle stability. Even at a high current density of 1 A g^-1, it still shows long-cycle life and maintains specific capacity of 190 mAh g^-1 after 3200 cycles. Furthermore, CoMoO₄@NC anode is applied to match with Na₃V₂(PO₄)₃ cathode to assemble full-cells, in which it accomplishes reversible capacity of 152 mAh g^-1 after 100 cycles, with capacity retention of 75% at a current density of 1 A g^-1, highlighting the practical application for SIBs.

The construction of CuCo2O4/N-doped reduced graphene oxide hybrid hollow spheres as anodes for sodium-ion batteries

Hierarchical CuCo₂O₄/N-doped reduced graphene oxide (CuCo₂O₄/N-rGO) hollow hybrid nanospheres was constructed and further applied as highly capacity anode materials for SIBs.

Kinetic and Electrochemical Reaction Mechanism Investigations of Rodlike CoMoO4 Anode Material for Sodium-Ion Batteries

Sodium-ion batteries are considered the most promising power source for electrical energy storage systems because of the abundance of sodium and their significant cost advantages. However, high-performance electrode materials are required for their successful application. Herein, we report a monoclinic-type CoMoO₄ material which is synthesized by a simple solution method. An optimized calcination temperature with a high crystallinity and a rodlike morphology of the material are selected after analyzing the as-synthesized powder by temperature-dependent time-resolved X-ray diffraction. The CoMoO₄ rods exhibit initial discharge and charge capacities of 537 and 410 mA h g^-1, respectively, when used as an anode for sodium-ion batteries. The sodium diffusion coefficient in the bimetallic CoMoO₄ anode is measured using the galvanostatic intermittent titration technique and calculated in the range of 1.565 × 10^-15 to 4.447 × 10^-18 cm² s^-1 during the initial cycle. Further, the reaction mechanism is investigated using ex situ X-ray diffraction and X-ray absorption spectroscopy, and the obtained results suggest an amorphous-like structure and reduction/oxidation of Co and Mo during the sodium insertion/extraction process. Ex situ transmission electron microscopy and energy-dispersive spectroscopy images of the CoMoO₄ anode in fully discharged and recharged state reveal the rodlike morphology with homogenous element distribution.

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

The interest in the development of micro-nanostructured metal oxides has been increasing recently because of their advantages as electrode materials in energy storage applications. In this study, dandelion-like ZnxCo3-xO4 microspheres assembled with porous needle-shaped nanosticks were synthesized by co-precipitation followed by a post-annealing treatment. The open space between neighboring nanosticks enables easy infiltration of the electrolyte; therefore, each nanostick is surrounded by the electrolyte solution, which ensures proper utilization of the active material during the electrochemical reaction. The dandelion-like ZnxCo3-xO4 hierarchical microspheres exhibit a greatly improved electrochemical performance with a high capacity and good cyclability as anodes for sodium-ion batteries (SIBs). A high initial reversible capacity of 612 mA h g-1 (at 35 mA g-1, ∼0.04C) is obtained and a capacity of 349 mA h g-1 is retained after 200 cycles. Meanwhile, the electrode shows a high rate performance with a capacity of 246 mA h g-1 at 2.0C-rate. The conversion of ZnxCo3-xO4 with Na is followed by ex situ X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) in different sodiation/de-sodiation states during electrochemical cycling. These analyses reveal that Na insertion/extraction is followed by complete reduction/oxidation of both metallic cobalt and zinc. The development of metallic Co and Zn after complete discharge and the formation of Co3O4 and ZnO when the electrode was fully recharged were identified by ex situ TEM analysis. In addition, the ZnxCo3-xO4 anode demonstrates feasible operation in a full cell by pairing with a NaNi2/3Bi1/3O2 cathode, affording a sodium-ion battery with an average working voltage of 2.6 V.

Carbon and Carbon Hybrid Materials as Anodes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have attracted much attention for application in large-scale grid energy storage owing to the abundance and low cost of sodium sources. However, low energy density and poor cycling life hinder practical application of SIBs. Recently, substantial efforts have been made to develop electrode materials to push forward large-scale practical applications. Carbon materials can be directly used as anode materials, and they show excellent sodium storage performance. Additionally, designing and constructing carbon hybrid materials is an effective strategy to obtain high-performance anodes for SIBs. In this review, we summarize recent research progress on carbon and carbon hybrid materials as anodes for SIBs. Nanostructural design to enhance the sodium storage performance of anode materials is discussed, and we offer some insight into the potential directions of and future high-performance anode materials for SIBs.