A Universal Strategy toward Air‐Stable and High‐Rate O3 Layered Oxide Cathodes for Na‐Ion Batteries

Abstract

As one of the fascinating high capacity cathodes, O3-type layered oxides usually suffer from their intrinsic air sensitivity and sluggish kinetics originating from the spontaneous lattice Na extraction during air exposure and high tetrahedral site energy of Na + diffusion transition state. What is worse, the improvement on the two handicaps is hard to simultaneously realize because of the contradiction between Na containment suggested in air stability mechanism and enhanced Na diffusion mentioned in kinetics strategy. Herein, it is shown that a simple strategy of introducing proper Na vacancies into lattice can simultaneously realize a dual performance improvement. Na vacancies decrease the charge density on transitional metal ions and enhance the antioxidative capability of material, ensuring a stable lattice Na containment for Na 0.93 Li 0.12 Ni 0.25 Fe 0.15 Mn 0.48 O 2 when exposed to air. Additionally, more Na + diffusional sites and enlarged Na layer spacing are obtained and result in a significantly decreased energy barrier from ≈1000 to 300 meV and a high rate capability of 70.8% retention at 2000 mA g −1 .Remarkably, such a strategy can be easily realized by either pre-or posttreating, which exhibits excellent universality for various O3 materials, implying its enormous potential to promote the commercial application of O3-type cathodes.

Completely suppressed high-voltage phase transition of P2/O3-Na0.7Li0.1Ni0.1Fe0.2Mn0.6O2viaLi/Ni co-doping for sodium storage

“…6e), reflecting the formation of hydrate phase during the air exposure. 45,46 By contrast, for the LN samples, no shift of the XRD reflection peaks is found, nor the new reflection peaks of the hydrate phase (Fig. 6f).…”

Intercalation Reaction in Amorphous Layer-Wrapped Ni0.2Mo0.8N/Ni3N Heterostructure Toward Efficient Lithium-Ion Storage

“…Moreover, there also exists a small amount of O element in the three materials, which could be attributed to surface oxidation and adsorbed water in air. For the A-NiMoN/Ni 3 N sample, the high-resolution Ni 2p XPS spectrum (Figure d) displays two peaks at lower binding energies (852.3 and 854.9 eV) and a couple of peaks at higher binding energies (869.5 and 872.5 eV), respectively, matching with the Ni 2p 3/2 and 2p 1/2 spin-orbit doublets. , The peaks at 852.3 and 869.5 eV can be assigned to the metallic Ni, and the peaks at 854.9 and 872.5 eV can be contributed to the Ni–N bonds . The XPS spectra of NiMoN/Ni 3 N-500 and NiMoN/Ni 3 N-550 are similar to that of A-NiMoN/Ni 3 N. Figure e shows the high-resolution Mo 3d XPS spectrum.…”

Synthesis, Structure, Electrochemical Mechanisms, and Atmospheric Stability of Mn-Based Layered Oxide Cathodes for Sodium Ion Batteries

“…To improve the air stability of Mn-based Na x TMO 2 , effective strategies typically aim to reduce the thermodynamic favorability of chemical and structural changes, such as doping, substitution, and composition modulation, or to avoid direct contact between active oxides and moisture by coating. − In addition, enhancing the moisture tolerance of layered oxides by structural engineering is proven to be effective at solving the poor air stability issue. ,, …”