Rigid-spring-network in P2-type binary Na layered oxides for stable oxygen redox

Realizing High-Performance Cathodes with Cationic and Anionic Redox Reactions in High-Sodium-Content P2-Type Oxides for Sodium-Ion Batteries

“…The typical charge/discharge GITT profile for the first cycle and the corresponding Na diffusion coefficients are shown in Figure f. The D Na + values of NLMC range from 10 –12 cm 2 s –1 to 10 –15 cm 2 s –1 , which is a moderate value for Na-deficient oxides. − Also, during charging, an obvious decrease of the Na diffusion coefficient was observed at high potential. In the anionic oxidation process, the preceding anionic activation plateau unavoidably causes some irreversible oxygen loss and permanently modifies the electrochemical profile due to the oxygen network distortion and rearrangement of TM ions.…”

Correlation of phase (in)stability and lattice misfits for high-power-density Na cathodes

“…29 These two issues helped us narrow down the vacancy content and understand the fundamental interplay between thermodynamic phase stability and cycle retention for P2-type Mn-Ni binary oxides, wherein the vacancy limit was assigned to x = 0.75, which excludes the oxygen anionic redox region. 32,47 The energy diagram of NM13 indicates a different charging pathway than that of NM12. The convex hull exhibited a monophasic reaction for a value below the vacancy limit in Na 1−x [Ni 3/12 Mn 9/12 ]O 2 , thus implying that no biphasic reaction occurred in pure Ni cationic redox.…”

Pulse-Assisted Low-Temperature Sintering to Enhance the Fast-Charging Capability for P2-Layered Na-Based Cathodes

“…X generally represents the partial substitution of Mn using alkali metals (Li + ), alkali earth metals (Mg 2+ , Zn 2+ ), and even vacancies. − Monovalent Li substitution has received considerable attention, which can be attributed to the restrained Jahn–Teller distortion via diluting the Mn 3+ content and the stabilized structure by reversible hopping between the TM layer and Na layer . Unfortunately, the P2-type sodium–manganese-based layered cathode with Na–O–Li configuration is still facing severe challenges, such as sluggish anionic kinetics, − irreversible surface oxygen release, and undesirable interfacial side reactions, eventually resulting in fast performance deterioration, which restricts its practical applications.…”

“…Efforts to promote diffusion kinetics and suppress surface oxygen release of ORR are mainly conducted by incorporating foreign dopants (Ca 2+ , Al 3+ , Ti 4+ , F – , etc.) or applying the surface coating. , However, it is hard to achieve complete uniformity with the common coating and doping modifications, or often some capacity is sacrificed, and the reported battery performance at fast-charge conditions is less satisfied.…”