Regulation of Coordination Chemistry for Ultrastable Layered Oxide Cathode Materials of Sodium-Ion Batteries.

Gao, Suning; Zhu, Zhuo; Fang, Hengyi; Feng, Kun; Zhong, Jun; Hou, Machuan; Guo, Yihe; Li, Fei et al. · Adv Mater · 2024

basic_science · Level V

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Abstract

Layered transition-metal (TM) oxide cathodes have attracted growing attention in sodium-ion batteries (SIBs). However, their practical implementation is plagued by Jahn-Teller distortion and irreversible cation migration, leading to severe voltage decay and structure instability. Herein, O3-Na<sub>0.898</sub>K<sub>0.058</sub>Ni<sub>0.396</sub>Fe<sub>0.098</sub>Mn<sub>0.396</sub>Ti<sub>0.092</sub>O<sub>2</sub> (KT-NFM) is reported as an ultrastable cathode material via multisite substitution with rigid KO<sub>6</sub> pillars and flexible TiO<sub>6</sub> octahedra. The K pillars induce contracted TMO<sub>2</sub> slabs and their strong Coulombic repulsion to inhibit Ni/Fe migration; and Ti incorporation reinforces the hybridization of Ni(3deg*)-O(2p) to mitigate the undesired O3-O'3 phase transition. These enable the reversible redox of Ni<sub>2</sub>+↔Ni<sub>3</sub> <sub>.</sub> <sub>20</sub>+ and Fe<sub>3</sub>+↔Fe<sub>3.69</sub>+ for 138.6 mAh g<sup>-1</sup> and ultrastable cycles with >90% capacity retention after 2000 cycles in a pouch cell of KT-NFM||hard carbon. This will provide insights into the design of ultrastable layered cathode materials of sodium-ion batteries and beyond.