Recent Advances and Prospects of Cathode Materials for Sodium‐Ion Batteries

Abstract

Sodium-ion batteries (SIBs) receive significant attention for electrochemical energy storage and conversion owing to their wide availability and the low cost of Na resources. However, SIBs face challenges of low specific energy, short cycling life, and insufficient specific power, owing to the heavy mass and large radius of Na(+) ions. As an important component of SIBs, cathode materials have a significant effect on the SIB electrochemical performance. The most recent advances and prospects of inorganic and organic cathode materials are summarized here. Among current cathode materials, layered transition-metal oxides achieve high specific energies around 600 mW h g(-1) owing to their high specific capacities of 180-220 mA h g(-1) and their moderate operating potentials of 2.7-3.2 V (vs Na(+) /Na). Porous Na3 V2 (PO4 )3 /C nanomaterials exhibit excellent cycling performance with almost 100% retention over 1000 cycles owing to their robust structural framework. Recent emerging cathode materials, such as amorphous NaFePO4 and pteridine derivatives show interesting electrochemical properties and attractive prospects for application in SIBs. Future work should focus on strategies to enhance the overall performance of cathode materials in terms of specific energy, cycling life, and rate capability with cationic doping, anionic substitution, morphology fabrication, and electrolyte matching.

Polyanion‐Type Electrode Materials for Sodium‐Ion Batteries

“…Taking phosphate as an example, it contains special tetrahedral PO 4 units with strong covalent bonding, which results in the relative isolation of valence electrons from polyanions 4. This special three‐dimensional (3D) stereostructure is quite favorable to the intercalation and deintercalation behavior of Na ions because the smaller energy orbit leaps from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), frequently accompanied by multi‐electron mechanisms 5. Therefore, understanding the unique electronic structure is a good way to develop practical polyanion‐type electrical materials for Na‐ion batteries 6…”

Sodium‐Ion Batteries: From Academic Research to Practical Commercialization

“…[29,30] During the long period of academic research on SIBs, there have been a number of achievements, especially on the active materials and electrolyte. Meanwhile, many review papers have also been published to describe different types of active materials and to analyze proposed reaction mechanisms, [31][32][33][34][35][36][37][38] which will not be discussed in this report in detail. From the perspective of future practical applications and commercialization, however, much more consideration should be paid to the sodium ion full-cell system rather than the halfcell system.…”

Flexible Electrodes for Sodium‐Ion Batteries: Recent Progress and Perspectives

“…In view of the rapidly booming attention on flexible SIBs, it is necessary to highlight the recent progress and perspectives. To the best of our knowledge, there have already been several excellent reviews devoted to SIBs [11][12][13][14][15][16] or flexible energy-storage devices, [17][18][19][20][21] but so far, there has been no comprehensive review focusing on flexible electrodes for SIBs up to now. Thus, the topic considered here is timely.…”

“…To address this problem, optimizing the chemical composition, tailoring the lattice structures, and regulating the morphologies of the host materials seem to be the most applicable strategies, and there have already been several excellent reviews. [11][12][13][14][15][16] As for technological innovation, the traditional fabrication processes mainly based on the slurrycasting method not only make SIBs typically rigid, thick, bulky, and heavy, but also reduce the overall volumetric/gravimetric energy density of the electrode. In the traditional slurry-casting method, the binders are insulating and electrochemically inactive, which can not only decrease the electrical conductivity, but also has a detrimental effect on the cycling stability resulting from some side effects between the electrolyte and inactive materials.…”