Degradation Mechanism of O3-Type NaNi_1/3Fe_1/3Mn_1/3O₂ Cathode Materials During Ambient Storage and Their In Situ Regeneration

Abstract

Sodium-ion batteries (SIBs) hold great promise for low-cost energy storage. Despite the major advances made in the material preparation and battery performance, air instability has become a bottleneck for the storage and electrode fabrication of O3-type NaNi1/3Fe1/3­Mn1/3O2 (NFM), but the underlying mechanism remains elusive. Here we discovered that NFM loses Na+ ions during ambient storage and Na2CO3 “fibers” sprout from the particle surface, which caused the performance decay. We further demonstrated a facile resintering strategy to regenerate the NFM in situ. This work highlights the importance of stringent humidity control and provides the basis for designing surface-modification strategies.

Surface-Modified Na(Ni0.3Fe0.4Mn0.3)O2 Cathodes with Enhanced Cycle Life and Air Stability for Sodium-Ion Batteries

“…The NaOH then reacts with carbon dioxide from air to become NaHCO 3 and subsequently Na 2 CO 3 . 20 Comparing the ADP and PA coating methods in Figure S9 shows that the 1 wt % PA method matches well with the uncoated sample. Therefore, the PA method does little to protect the material from bulk degradation.…”

“…15−19 In addition to surface reactions with the electrolyte during cycling, this material also suffers from poor stability in air and moisture, which makes processing, storage, and transportation challenging and expensive, limiting the practical application of this material. 4,20,21 To mitigate the challenges in both the electrolyte and air, surface modification is necessary to protect against these deleterious reactions.…”

“…This material can achieve up to 165 mA h g –1 at low rates and high voltages, or it can achieve high cycle life by severely limiting specific capacity. , To achieve a specific capacity of above 100 mA h g –1 in addition to good cycle life, further material modification is necessary. Recent studies evaluating the degradation mechanisms of this material suggest that the primary cause of capacity fade below 4 V (all voltages are versus sodium metal) is due to surface reactivity. − In addition to surface reactions with the electrolyte during cycling, this material also suffers from poor stability in air and moisture, which makes processing, storage, and transportation challenging and expensive, limiting the practical application of this material. ,, To mitigate the challenges in both the electrolyte and air, surface modification is necessary to protect against these deleterious reactions.…”

Iron‐Based Layered Cathodes for Sodium‐Ion Batteries

“…[114,115] However, more in-depth investigations are still needed to fully understand the capacity fading of NaNi 1/3 Fe 1/3 Mn 1/3 O 2 , so as to figure out targeted approaches for further improvements. [116] Notably, supported by synchrotron-based analysis, Jeong and co-workers claimed that O3-P3 phase transition only majorly under charging voltage of 4.0 V, while Ni 2 + /Ni 4 + redox couple contributes most of capacity in this region. [117] When charged above 4.0 V, Fe 3 + / Fe 4 + reactions become dominant, leading to increased distortion of local structure for Fe.…”

“…Coating with stable surface layers, e. g. MnO 2 and ZrO 2 , are proposed as a potential way to solve this problem. [116,121]…”