Sodium Composite Oxide Cathode Materials:Phase Regulation, Electrochemical Performance and Reaction Mechanism

Abstract

The abundance of sodium resources provides the basis for the large‐scale application of sodium‐ion batteries (SIBs) in the field of energy storage. Among the cathode candidates for SIBs, oxide materials stand out because of their ease of synthesis, environmental friendliness and high capacity. According to the crystal structure, oxide cathode materials can be mainly classified as P2, P3, O3 and tunnel phases. Benefiting from the combined advantages of different phases, composite oxide cathode materials have been widely studied due to the enhanced both cycling and rate performance. In this review, we analyzed the three key issues of phase regulation, electrochemical performance and reaction mechanism based on the recent progress for composite oxide cathode materials. The composite oxide cathode materials will be one of the most competitive and attractive cathodes for SIBs.

Suppressing the P2‐O2 phase transition and Na+/vacancy ordering in Na0.67Ni0.33Mn0.67O2 by a delicate multicomponent modulation strategy

“…However, the limitation of lithium resources and soaring cost hinder the application of LIBs, compelling the development of cost‐effective alternative techniques 9 . Up to now, many categories of alternatives have been studied, including sodium ion batteries, potassium ion batteries, zinc ion batteries and so on 10–12 . Recently, sodium‐ion batteries (SIBs) have received significant attention by similar working mechanisms with LIBs as well as the abundance of sodium resources.…”

“…9 Up to now, many categories of alternatives have been studied, including sodium ion batteries, potassium ion batteries, zinc ion batteries and so on. [10][11][12] Recently, sodium-ion batteries (SIBs) have received significant attention by similar working mechanisms with LIBs as well as the abundance of sodium resources. However, developing suitable cathode materials for SIBs is still a challenge due to the unsatisfactory capacity and stability caused by the larger radius (1.02 Å vs. 0.76 Å) and heavier mass (23 g mol −1 vs. 6.9 g mol −1 ) compared with lithium ions, which immensely restricts its practical application.…”

Unprecedented Cyclability and Moisture Durability of NaCrO2 Sodium-Ion Battery Cathode via Simultaneous Al Doping and Cr2O3 Coating

“…However, the relatively low electronic conductivity of polyanion-type cathodes often compromises these advantageous features, leading to insufficient rate capabilities, unless surface or morphological modifications are made. On the other hand, relatively high electronic/ionic conductivities of layered transition-metal oxides enable fast charge/discharge (C/D), but multiple phase transitions during C/D often degrade the cyclability. , Humidity sensitivity also complicates electrode fabrication and/or long-term storage …”

“…1 Despite continuous technological improvements, the overall performance of NIBs still lags behind LIBs, although certain properties of battery components have become comparable to those used in state-of-the-art LIBs. 2 In terms of cathode materials, polyanion-type compounds 3 and layered transition-metal oxides 4 are two representative examples that have undergone numerous modifications in terms of elemental compositions, crystallographic structures, and particle morphologies. Polyanion-type compounds (e.g., phosphates, 5 pyrophosphates, 6 fluorophosphates, 7 NASICON structures, 8 sulfates, 9 and silicates 10 ) are generally composed of tetrahedron anionic units interconnected with transition-metal polyhedral units, which contribute to high operating potential and cyclic stability.…”

“…However, the relatively low electronic conductivity of polyanion-type cathodes often compromises these advantageous features, leading to insufficient rate capabilities, 11 conductivities of layered transition-metal oxides enable fast charge/discharge (C/D), but multiple phase transitions during C/D often degrade the cyclability. 4,12 Humidity sensitivity also complicates electrode fabrication and/or long-term storage. 13 O3-NaCrO 2 is a highly promising cathode material in the class of layered transition-metal oxides due to its reversible capacity, almost constant C/D voltages, and excellent thermal stability.…”