On Disrupting the Na⁺-Ion/Vacancy Ordering in P2-Type Sodium–Manganese–Nickel Oxide Cathodes for Na⁺-Ion Batteries

Abstract

An investigation of the electrochemical and structural properties of layered P2–Na0.62Mn0.75Ni0.25O2 is presented. The effect of changing the Mn/Ni ratio (3:1) from what is found in Na0.67Mn0.67Ni0.33O2 (2:1) and consequently the introduction of a third metal center (Mn3+) was investigated. X-ray powder diffraction (in situ and ex situ) revealed the lack of Na+-ion/vacancy ordering at the relevant sodium contents (x = 0.33, 0.5, and 0.67). Mn3+ in Na0.62Mn0.75Ni0.25O2 introduces defects into the Ni–Mn interplane charge order that in turn disrupts the ordering within the Na-plane. The material underwent P2–O2 and P2–P2′ phase transitions at high (4.2 V) and low (∼1.85 V) voltages, respectively. The material was tested at several different voltage ranges to understand the effect of the phase transitions on the capacity retention. Interestingly, the inclusion of both phase transitions demonstrated comparable cycling performance to when both phase transitions were excluded. Last, excellent rate performance was demonstrated between 4.3 and 1.5 V with a specific capacity of 120 mA h/g delivered at 500 mA/g current density.

Probing the charged state of layered positive electrodes in sodium-ion batteries: reaction pathways, stability and opportunities

“…P2-O2) and therefore leads to an improvement in the battery performance. 32 The OP4-type phase was rst reported for the P2-Na 0.67 -Fe 0.5 Mn 0.5 O 2 material, upon charging above 4.1 V. It was found to transition into a less crystalline phase with OP4-type stacking (Fig. 3).…”

Dopant and Current Rate Dependence on the Structural Evolution of P2‐Na2/3Mn0.8Zn0.1M0.1O2 (M=Cu, Ti): An Operando Study

“…In a comparative study, Gutierrez et al. detected LZZ ordering in P2‐ Na 0.67 Mn 0.67 Ni 0.33 O 2 but not P2‐ Na 0.67 Mn 0.75 Ni 0.25 O 2 [22b] . It was therefore proposed that increasing the concentration of higher energy Mn−Na‐Mn sites disrupts the LZZ Na/vacancy ordering, which is likely the case for P2‐ Na 2/3 Mn 0.8 Zn 0.1 Cu 0.1 O 2 as well.…”

Recent Advances in Layered Metal‐Oxide Cathodes for Application in Potassium‐Ion Batteries

“…The large difference between the ionic radii of the transition metal ions induces metal ordering, while the smaller difference between the redox potentials of the metal ions induces charge ordering. [90,152,153] Therefore, suppressing K + /vacancy ordering to produce a disordered K + /vacancy structure is important to enhance battery performance. Wang et al [154] developed cation-disordered P2-Na 0.6 [Cr 0.6 Ti 0.4 ]O 2 by doping with Cr 3+ and Ti 4+ , which have similar ionic radii but different redox potentials.…”