Lattice sulfuration enhanced sodium storage performance of Na 0.9 Li 0.1 Zn 0.05 Ni 0.25 Mn 0.6 O 2 cathode

Introducing lattice oxygen redox for charge compensation in layered metal oxides is an effective way to develop advanced cathodes for high energy density sodium-ion batteries (SIBs). However, the asymmetry of lattice oxygen oxidation and reduction incurs oxygen release and crystal structure rearrangement, leading to poor reversibility of the charge and discharge process. Herein, a Na2S-assisted sulfuration strategy is firstly proposed to incorporate active sulfur into the crystal lattice of Na 0.9 Li 0.1 Zn 0.05 Ni 0.25 Mn 0.6 O 2 cathode. The sulfur anions within the interior lattice participate in the redox process and enhance the integral coordination stability by mitigating undesired excessive oxygen redox, while the exterior sulfur forms a polyanionic layer to protect the particle surface against electrolyte corrosion. The incorporation of an extra redox center efficiently facilitates the increase of the discharge capacity from 159.9 to 179.2 mAh g _ 1 within the voltage range of 1.5-4.5 V. Moreover, the larger ionic radius of sulfur enlarges the interplanar spacing, thus facilitating Na+ ions transfer, especially at high current density. As a result, the modified cathode exhibits significantly enhanced electrochemical performance, with a capacity retention of 87 % after 100 cycles at 0.2 C and an excellent rate capability of 98.0 mAh g _ 1 at 10 C. Moreover, the assembled Na ion full cell based on a commercial hard carbon anode achieves an impressive capacity of 160.4 mAh g _ 1 at 0.1 C and could cycled steadily for over 100 cycles. The modification of layer oxides via sulfuration strategy provides a promising pathway for the structural design of novel cathodes with superior cycle performance for high-energy-density SIBs applications.