A high-rate material for sodium-ion batteries: Bi/Zr Co-doped Na0.44Mn0.97Bi0.01Zr0.02O2/CNT composites

Abstract

Among the diverse cathode materials for sodium-ion batteries (SIBs), Na_0.44MnO₂ has gained significant attention due to its stable 3D tunneling structure, low cost, and promising electrochemical performance. However, its widespread application is limited by poor diffusion kinetics and insufficient rate capability. Traditional doping or surface modification techniques often fail to adequately address these challenges. In this work, we present an innovative strategy that combines Bi and Zr co-doping with the incorporation of carbon nanotubes (CNT) to improve the electrochemical performance of Na_0.44MnO₂. Na_0.44Mn_0.97Bi_0.01Zr_0.02O₂/CNT composites were synthesized via a combination of solid-state reactions and spray-drying methods. The co-doping of Bi and Zr significantly improves the diffusion kinetics of and enhances cycling stability, while the CNT improve electronic conductivity, resulting in outstanding rate capability and cycling stability. The composite delivers a high discharge capacity of 102.26 mAh g⁻¹, maintaining 87.2 % of its initial capacity after 1000 cycles and 72.4 % after 2000 cycles at 5C, showcasing exceptional high-rate cycling performance. This study presents an effective strategy for enhancing Na_0.44MnO₂ cathodes and offers important insights for the development of advanced energy storage technologies.