Ni-driven monoclinic → P2 → O3 phase evolution in NaMn1−xNixO2 cathodes: structural origin, sodium storage and hard carbon full cells
8 affiliations
- 1Department of Physics, Inonu University Battalgazi Malatya 44280 Türkiye
- 2Department of Chemistry, Quaid-i-Azam University Islamabad 45320 Pakistan
- 3National Center of Physics, Quaid-i-Azam University Islamabad 45320 Pakistan
- 4Physics Engineering Department, Istanbul Medeniyet University Istanbul 34700 Türkiye
- 5Department of Chemistry, Bogazici University Bebek Istanbul 34342 Türkiye
- 6TÜBİTAK Rail Transport Technologies Institute, Energy Storage Division TÜBİTAK Gebze Campus Kocaeli 41470 Türkiye
- 7Battery Technology Application and Research Center, Inonu University Battalgazi Malatya 44280 Türkiye
- 8Physics Engineering Department, Istanbul Technical University Istanbul Türkiye
Abstract
In this study, NaMn1−xNixO2 (x = 0–0.5) compositions were synthesized by a solid-state method, and their structural evolution and electrochemical performance for sodium-ion batteries were systematically investigated. X-ray diffraction studies reveal that increasing Ni content induces a structural transition from the monoclinic (C2/m) phase to the hexagonal P2-type (P63/mmc) and eventually the rhombohedral (R3̄m, O3-type) phase. ICP-MS analysis reveals Na/TM molar ratios of 0.839–0.905, showing that Na loss during calcination contributes to the stabilization of the P2 phase at intermediate Ni contents. While the C2/m and P63/mmc phases coexist in the x = 0.1 and 0.2 samples, a pure P63/mmc phase is observed in x = 0.3. As the Ni substitution is increased further, the R3̄m phase forms together with a minor NiO impurity. Density functional theory (DFT) calculations indicate that the monoclinic phase is thermodynamically favored at low Ni contents, whereas the rhombohedral phase becomes increasingly competitive as the Ni content increases, in line with the experimental trend. Structural analysis shows that upon Ni substitution the number of Mn3+ ions is reduced, which removes the cooperatively Jahn–Teller distorted monoclinic phase, although XPS shows that Jahn–Teller active Ni3+ is present at x = 0.5 without inducing a cooperative distortion, and oxygen lattice ordering is improved. These structural modifications indicate a stabilized layered framework. Electrochemical measurements show that appropriate Ni substitution improves capacity retention and rate capability where the x = 0.5 sample exhibits the best cycling stability. Finally, the optimized cathode was utilized in a full-cell configuration with a hard carbon anode where the P/N ratio and anode presodiation are tailored as a proof of concept. The low initial coulombic efficiency (49.34–56.08%) shows that the Na inventory of the full cell still requires further optimization.
Related
- Visible-Light-Driven Photoreduction of Industrial-Grade Graphene Oxide into Single-/Few-Layer Reduced Graphene Oxide Nanosheets: Structural Evolution and Enhanced Electrochemical Energy-Storage Performance
- Unraveling the charge-storage mechanism of microporous carbon cathodes in LiCl-saturated chloroaluminate ionic liquid electrolytes for aluminum-ion batteries
- Structural analysis of Helicobacter pylori glutamate racemase in a monoclinic crystal form
- Rapid One-Step Synthesis of Sodium-Ion Battery Cathodes from Desalination Waste: A Sustainable Approach to High-Performance Energy Storage
- Site-Selective Yttrium Substitution in Ti3AlC2 Enables Interlayer Engineering and Li Transport in Ti3C2Tx cathodes for High-Power Energy Storage
BibTeX
@article{dogan2026nidriven,
title = {{Ni-driven monoclinic → P2 → O3 phase evolution in NaMn1−xNixO2 cathodes: structural origin, sodium storage and hard carbon full cells}},
author = {Ebru Dogan and Abdoul Hadi Maiga and Abdul Naveed and Muhammad Arshad and Fatih Bulut and Semran Ipek and Sümeyye Cörüt and Mehmet Nurullah Ates and Serdar Altin and Sevda Sahinbay},
journal = {RSC advances},
year = {2026},
month = oct,
doi = {10.1039/d6ra08511c},
url = {https://europepmc.org/article/PMC/PMC13721914},
note = {CC BY-NC},
}
RIS
TY - JOUR
TI - Ni-driven monoclinic → P2 → O3 phase evolution in NaMn1−xNixO2 cathodes: structural origin, sodium storage and hard carbon full cells
AU - Ebru Dogan
AU - Abdoul Hadi Maiga
AU - Abdul Naveed
AU - Muhammad Arshad
AU - Fatih Bulut
AU - Semran Ipek
AU - Sümeyye Cörüt
AU - Mehmet Nurullah Ates
AU - Serdar Altin
AU - Sevda Sahinbay
PY - 2026
DA - 2026/10/30
JO - RSC advances
DO - 10.1039/d6ra08511c
UR - https://europepmc.org/article/PMC/PMC13721914
AB - In this study, NaMn1−xNixO2 (x = 0–0.5) compositions were synthesized by a solid-state method, and their structural evolution and electrochemical performance for sodium-ion batteries were systematically investigated. X-ray diffraction studies reveal that increasing Ni content induces a structural transition from the monoclinic (C2/m) phase to the hexagonal P2-type (P63/mmc) and eventually the rhombohedral (R3̄m, O3-type) phase. ICP-MS analysis reveals Na/TM molar ratios of 0.839–0.905, showing that Na loss during calcination contributes to the stabilization of the P2 phase at intermediate Ni contents. While the C2/m and P63/mmc phases coexist in the x = 0.1 and 0.2 samples, a pure P63/mmc phase is observed in x = 0.3. As the Ni substitution is increased further, the R3̄m phase forms together with a minor NiO impurity. Density functional theory (DFT) calculations indicate that the monoclinic phase is thermodynamically favored at low Ni contents, whereas the rhombohedral phase becomes increasingly competitive as the Ni content increases, in line with the experimental trend. Structural analysis shows that upon Ni substitution the number of Mn3+ ions is reduced, which removes the cooperatively Jahn–Teller distorted monoclinic phase, although XPS shows that Jahn–Teller active Ni3+ is present at x = 0.5 without inducing a cooperative distortion, and oxygen lattice ordering is improved. These structural modifications indicate a stabilized layered framework. Electrochemical measurements show that appropriate Ni substitution improves capacity retention and rate capability where the x = 0.5 sample exhibits the best cycling stability. Finally, the optimized cathode was utilized in a full-cell configuration with a hard carbon anode where the P/N ratio and anode presodiation are tailored as a proof of concept. The low initial coulombic efficiency (49.34–56.08%) shows that the Na inventory of the full cell still requires further optimization.
SN - 2046-2069
ER -