An advanced medium-entropy substituted tunnel-type Na0.44MnO2 cathode for high-performance sodium-ion batteries

Abstract

Because of the irreversible reaction and sluggish migration rate of Na ions during the electrochemical process, the cycling stability and rate capability of tunnel-type Na_0.44MnO₂ are poor. In this work, it is discovered that medium-entropy substitution can significantly increase cycling stability and rate capability. The prepared cathode Na_0.44Mn_0.97Al_0.01Ti_0.01Co_0.01O₂ exhibits an enhanced rate capability of 80 mA h g⁻¹ at 20C and demonstrates a high discharge capacity of 78 mA h g⁻¹ after 2000 cycles at 10C, with a high capacity retention of approximately 80%. The mechanism of the improved electrochemical performance of Na_0.44MnO₂ by the medium-entropy substitution strategy is deeply studied. The medium-entropy substitution increases the spacing of lattice fringes and replaces manganese, resulting in improved rate capability and cycling performance of Na_0.44MnO₂. The discovered medium-entropy Na_0.44MnO₂ material provides new insight into the development of tunnel-type electrode materials and promotes their application in rechargeable Na-ion batteries.