Synergistic electronic and crystal structure regulation of Na2+2xFe2−x(SO4)3via Zr doping for high-performance sodium-ion batteries

Abstract

Na_2.5Fe_1.71Zr_0.02(SO₄)₃ with a synergistically optimized electronic and crystal structure is designed for high-performance sodium ion batteries. The orbital interaction induced by Zr doping significantly improves its intrinsic conductivity. Additionally, the longer Na–O bonds after Zr doping accelerate the Na⁺ transfer kinetics. Ultimately, Na_2.5Fe_1.71Zr_0.02(SO₄)₃ exhibits a high specific capacity of 96.4 mAh g⁻¹ at 0.1C with 85% retention after 10 000 cycles at 30C.