Elucidation of the sodium kinetics in layered P-type oxide cathodes

Inhibition of the P3–O3 phase transition via local symmetry tuning in P3-type layered cathodes for ultra-stable sodium storage

“…2f). 11,17,19,20,25,28,36–38 Therefore, these results strongly demonstrate that compositional regulation plays an important role in enhancing the cycling stability and rate performance.…”

“…In the previous work, with the P3-NaNM charged to the second voltage platform at 0.1C, this P3–O3 phase transformation can be observed and subsequently exhibits a symmetric phase transition in the whole charge/discharge process. 20 However, we find that the structural evolution of the P3-NaNM cathode upon Na + extraction and insertion shows distinctive asymmetry at 0.2C, which is possible because the P3–O3 phase transition kinetics are very sluggish. The refined lattice parameters, especially a and c , further confirmed that Na + cannot return to its original state under the same voltage conditions after the first discharge, indicating that the structural changes caused by the (de)intercalation of Na + are irreversible.…”

“…17,18 However, the P3 cathode, taking P3-Na 2/3 Ni 1/3 Mn 2/3 O 2 (P3-NaNM) for example, usually suffers from the P3–O′3 irreversible phase transition at a high voltage of 4.25 V, leading to the fast capacity decay during the desodiation/sodiation process. 19,20 Current research studies suggest that the regulation of the TMO 2 layer through the introduction of Mg 2+ can strengthen the preservation of Na + in prismatic sites to stabilize the overall charge balance of the cathode, thereby effectively enhancing the high-voltage stability. 21,22 However, apart from the issue of this irreversible phase transition, there still exists a different ordering structure below 4.25 V, including Na + /vacancy ordering within the Na layer and charge ordering and cationic ordering on the TM lattice.…”

Constructing a Composite Structure by a Gradient Mg2+ Doping Strategy for High-Performance Sodium-Ion Batteries

“…Sodium-ion batteries (SIBs) have been deemed as an appealing alternative for electrochemical energy storage systems on a large scale by virtue of the analogous working principle with lithium-ion batteries (LIBs), abundant reserves, and attractive cost. − Moreover, cathode materials are of great significance in determining the operating voltage and energy density. − Among many cathode materials, layered transition metal oxides possess high specific capacity, cost effectiveness, and convenience for large-scale preparation. − In particular, P2-type Na 0.67 Mn 0.67 Ni 0.33 O 2 (P2-NMNO) materials are supposed to be an attractive cathode alternative for commercialization due to the high voltage profile (average voltage ≥3.5 V), high specific capacity, and good stability in an ambient atmosphere and moisture. , Nevertheless, bulk failure caused by the high-voltage P2–O2 phase transformation (4.2 V vs Na + /Na) results in large volume expansion and contraction. This not only causes inferior Na + diffusion kinetics but also gives rise to the initiation and propagation of cracks .…”

“…10−15 In particular, P2type Na 0.67 Mn 0.67 Ni 0.33 O 2 (P2-NMNO) materials are supposed to be an attractive cathode alternative for commercialization due to the high voltage profile (average voltage ≥3.5 V), high specific capacity, and good stability in an ambient atmosphere and moisture. 16,17 Nevertheless, bulk failure caused by the high-voltage P2−O2 phase transformation (4.2 V vs Na + /Na) results in large volume expansion and contraction. This not only causes inferior Na + diffusion kinetics but also gives rise to the initiation and propagation of cracks.…”