TY - JOUR
T1 - Compositional tuning of Fe/Mn and Fe/Ni ratios in P3-type cathodes enables high energy density sodium-ion batteries
AU - Saxena, Samriddhi
AU - Dagar, Neha
AU - Srihari, Velaga
AU - Chinnathambi, Karthik
AU - Das, Asish Kumar
AU - Gami, Pratiksha
AU - Deswal, Sonia
AU - Kumar, Pradeep
AU - Poswal, Himanshu Kumar
AU - Kumar, Sunil
N1 - Publisher Copyright:
© 2025 Elsevier Ltd
PY - 2025/10
Y1 - 2025/10
N2 - Layered oxide cathodes are promising candidates for sodium-ion batteries due to their high theoretical capacity and structural tunability. However, irreversible high-voltage redox reactions and structural degradation hinder their practical deployment. In this study, a series of Na0.8(Mn–Fe–Ni)O2 cathodes with systematically varied Fe/Mn and Fe/Ni ratios is investigated to uncover the role of transition metal composition in governing redox behavior, phase transitions, and long-term performance across 2.0–4.0 V and 2.0–4.4 V. Structural analyses reveal that increasing Fe/Mn ratio expands Na-O2 layer spacing and strengthens TM–O bonds, indicating reduced anionic activity and improved structural stability. Na0.8Mn0.53Fe0.25Ni0.22O2 delivers the highest specific capacity (153 mAh g−1), specific energy (500.3 Wh kg−1), and reversible high-voltage redox activity, retaining 92.6 % of its capacity after 100 cycles at 0.2C (2.0–4.4 V). Operando Synchrotron X-ray diffraction confirms P3/O3↔P3″/O3 transformations with minimal lattice strain (Δc=[Formula presented]×100% = −1.81 % for O3, +1.00 % for P3), contributing to enhanced high-voltage cyclability in Na0.8Mn0.53Fe0.25Ni0.22O2. Meanwhile, Na0.8Mn0.64Fe0.14Ni0.22O2 exhibits exceptional cycling performance (99 % retention) in the 2.0–4.0 V range, benefiting from a P3↔P3′ transition. These findings highlight the critical role of Fe/Mn and Fe/Ni tuning in balancing redox reversibility and structural integrity, offering a rational design strategy for high-energy, long-life sodium-ion cathodes.
AB - Layered oxide cathodes are promising candidates for sodium-ion batteries due to their high theoretical capacity and structural tunability. However, irreversible high-voltage redox reactions and structural degradation hinder their practical deployment. In this study, a series of Na0.8(Mn–Fe–Ni)O2 cathodes with systematically varied Fe/Mn and Fe/Ni ratios is investigated to uncover the role of transition metal composition in governing redox behavior, phase transitions, and long-term performance across 2.0–4.0 V and 2.0–4.4 V. Structural analyses reveal that increasing Fe/Mn ratio expands Na-O2 layer spacing and strengthens TM–O bonds, indicating reduced anionic activity and improved structural stability. Na0.8Mn0.53Fe0.25Ni0.22O2 delivers the highest specific capacity (153 mAh g−1), specific energy (500.3 Wh kg−1), and reversible high-voltage redox activity, retaining 92.6 % of its capacity after 100 cycles at 0.2C (2.0–4.4 V). Operando Synchrotron X-ray diffraction confirms P3/O3↔P3″/O3 transformations with minimal lattice strain (Δc=[Formula presented]×100% = −1.81 % for O3, +1.00 % for P3), contributing to enhanced high-voltage cyclability in Na0.8Mn0.53Fe0.25Ni0.22O2. Meanwhile, Na0.8Mn0.64Fe0.14Ni0.22O2 exhibits exceptional cycling performance (99 % retention) in the 2.0–4.0 V range, benefiting from a P3↔P3′ transition. These findings highlight the critical role of Fe/Mn and Fe/Ni tuning in balancing redox reversibility and structural integrity, offering a rational design strategy for high-energy, long-life sodium-ion cathodes.
KW - Biphasic P3/O3
KW - Energy density
KW - Layered oxides
KW - Operando Synchrotron XRD
KW - Sodium-ion batteries
UR - https://www.scopus.com/pages/publications/105015297793
U2 - 10.1016/j.mtener.2025.102048
DO - 10.1016/j.mtener.2025.102048
M3 - Article
AN - SCOPUS:105015297793
SN - 2468-6069
VL - 53
JO - Materials Today Energy
JF - Materials Today Energy
M1 - 102048
ER -
