Multiple effects of Mg1–xNixO coating on P2-type Na0.67Ni0.33Mn0.67O2 to generate highly stable cathodes for sodium-ion batteries

Hyeongwoo Kim, Jae Ho Park, Sung Chul Kim, Dongjin Byun, Kyung Yoon Chung, Hyung Seok Kim, Wonchang Choi

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

P2-type Na0.67Ni0.33Mn0.67O2 (NNMO) is a state-of-the-art, high-energy and high-voltage cathode material in sodium-ion batteries. However, surface degradation effects, such as P2–O2 phase transformation, ordering of Na+/vacancy, electrolyte decomposition, and HF attack, limit its electrochemical stability. To counter these effects, we applied Mg1–xNixO (MgNiO) as a coating formed via wet-chemical coating to suppress unfavorable side reactions; surface doping of Mg2+ also occurs post-calcination, which is expected to reduce P2–O2 transition near the surface structure. MgNiO-NNMO exhibited outstanding cycling stability (70.08 mAh g−1 over 200 cycles) and rate capability (39.41 mAh g−1 at 5C over 800 cycles). The influence of Mg2+ doping was studied comprehensively through in situ and ex situ X-ray diffraction analysis. Furthermore, to characterize the protective role of the MgNiO coating in harsh conditions, we operated NNMO as Na half cells at a high temperature of 60 °C and high voltage of 4.5 V (vs. Na+/Na) for the first time; under these conditions, MgNiO-NNMO exhibited remarkable cycling stability (52.68 mAh g−1 over 100 cycles) as compared to pristine NNMO (7.213 mAh g−1 over 100 cycles). Surface analysis via X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy were also conducted to investigate the impact of electrolyte decomposition and HF attack.

Original languageEnglish
Article number157294
JournalJournal of Alloys and Compounds
Volume856
DOIs
Publication statusPublished - 2021 Mar 5

Keywords

  • Cathode materials
  • MgNiO
  • NaNiMnO
  • Sodium-ion batteries
  • Surface modification

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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