Manganese based layered oxides with modulated electronic and thermodynamic properties for sodium ion batteries

Abstract

Manganese based layered oxides have received increasing attention as cathode materials for sodium ion batteries due to their high theoretical capacities and good sodium ion conductivities. However, the Jahn–Teller distortion arising from the manganese (III) centers destabilizes the host structure and deteriorates the cycling life. Herein, we report that zinc-doped Na0.833[Li0.25Mn0.75]O2 can not only suppress the Jahn–Teller effect but also reduce the inherent phase separations. The reduction of manganese (III) amount in the zinc-doped sample, as predicted by first-principles calculations, has been confirmed by its high binding energies and the reduced octahedral structural variations. In the viewpoint of thermodynamics, the zinc-doped sample has lower formation energy, more stable ground states, and fewer spinodal decomposition regions than those of the undoped sample, all of which make it charge or discharge without any phase transition. Hence, the zinc-doped sample shows superior cycling performance, demonstrating that zinc doping is an effective strategy for developing high-performance layered cathode materials.

Highly Electrochemically‐Reversible Mesoporous Na2FePO4F/C as Cathode Material for High‐Performance Sodium‐Ion Batteries

“…The larger ionic radius of sodium ion (1.02 Å) compared to lithium ion (0.76 Å), however, has been regarded as the greatest challenge to hinder the performance improvement of sodium‐ion batteries . In the past ten years, a lot of works focused on seeking for appropriate Na + ‐host materials, such as transition‐metal oxides, phosphates, and ferrocyanides . Among them, the Fe‐based phosphate is one of the most concerned cathode materials due to its low cost and abundant resources .…”

Designing Advanced Vanadium‐Based Materials to Achieve Electrochemically Active Multielectron Reactions in Sodium/Potassium‐Ion Batteries

“…Also, since both sodium and potassium have large ionic radii, strong Na + −Na + /K + −K + interactions will occur, and this phenomenon requires strongly hybridized orbitals of central elements to accommodate them. [ 36 ] Manganese is another ideal element to address this issue; [ 37–41 ] but the Jahn–Teller effect of Mn 3+ (both octahedral high spin and low spin d 4 electrons) cannot be perfectly avoided during electrochemical processes, which will lead to unstable local coordination structures and inferior cycling performance. [ 42 ] Vanadium only possesses three d‐orbital electrons and will not be bothered by this issue.…”

Understanding Challenges of Cathode Materials for Sodium‐Ion Batteries using Synchrotron‐Based X‐Ray Absorption Spectroscopy

“…The soft XAS spectra indicated that the increased Cu content could enhance the metal to ligand charge transfer (MLCT) effect, and the O K‐edge also showed that Cu−O becomes a redox centre compensating for charge neutrality (as a result of Fe ion migration). It can be deduced that other transition metal elements such as Zn, Ti, and Ru will also have positive effects on the voltage decay mentioned above . Multiple element doping can also reduce the Jahn‐Teller effect.…”

“…Mn is troublesome sometimes since the strong Jahn‐Teller effect from manganese (III) centres can destabilize host structures. Very recently, Kang's group reported that Li/Zn substitution can be an effective way to reduce the inherent phase separation . A high binding energy was confirmed, and octahedral structure variations were reduced.…”

“…(c) Crystal structure of Zn‐doped P2‐type NLMO along the [001] orientation. Reprinted with permission from (a)–(c) . Copyright 2019 Springer Nature.…”