Closed-shell elements Li & Sn substituted P2-type layered cathode materials for wide-voltage sodium-ion batteries

초록

Layered transition metal oxide cathode materials have garnered increasing attention for sodium-ion batteries (SIBs). However, they are plagued by the Jahn-Teller distortion of MnO6, Na+/vacancy ordering, and irreversible lattice oxygen loss, which collectively lead to capacity fading and voltage decay. Herein, we report a P2-type material, Na0.67Ni0.3Mn0.6Li0.09Sn0.01O2 (NNMO-Li0.09Sn0.01), modified with two closed-shell dopants (i.e., Li+ and Sn4+). Benefiting from the unique electronic configurations of closed-shell ions, NNMO-Li0.09Sn0.01 exhibits enhanced structural and electrochemical stability. Specifically, the incorporation of Li+ increases the Mn4+/Mn3+ ratio, thereby mitigating Jahn-Teller distortion during (de)sodiation process. In addition, Li+ disrupts the Ni/Mn ordering in the transition metal layer, suppressing Na+/vacancy ordering. Meanwhile, the introduction of Sn4+ forms stronger Sn-O bonds (548 kJ mol-1), thereby enhancing the bonding strength between neighboring transition metal ions and surrounding oxygen atoms, effectively reducing oxygen loss during cycling. NNMO-Li0.09Sn0.01 exhibits significantly improved cycling stability, delivering a specific capacity of 90.3 mAh g-1 with 62.9% capacity retention after 50 cycles at 0.1 C (1 C = 200 mA g-1), along with 90.3% voltage retention. This substitution strategy based on closed-shell ions offers a viable approach for enhancing the structural stability of wide-voltage layered oxide cathodes. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)Jahn-Teller(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic), (sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)Li+,Sn4+ (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)P 2 (sic) Na0.67Ni0.3Mn0.6Li0.09Sn0.01O2 (NNMO-Li0.09Sn0.01)(sic)(sic), (sic)(sic)Li+ (sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)Jahn-Teller(sic)(sic), (sic)(sic)(sic)(sic)Na+/(sic)(sic)(sic)(sic)(sic)Sn4+ (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)Sn-O(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)O (sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(Na0.67Ni0.33Mn0.67O2 NNMO)(sic)(sic), NNMO-Li0.09Sn0.01(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)0.1 C (1 C = 200 mA g-1)(sic)(sic)(sic)50(sic)(sic)(sic)(sic)(sic)(sic)90.3 mAh g-1 (62.9%), (sic) NNMO(sic)(sic)63.0 mAh g-1 (39.0%), (sic)(sic)NNMO-Li0.09Sn0.01(sic)(sic)(sic)50 (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)90.3%, (sic)NNMO(sic)(sic)84.1%. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

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