Preparation and Electrochemical Performance of Carbon-coated Na_0.44MnO₂ Cathode Material Synthesized by One-step Method

Taking MnCO₃ as manganese source and Na₃C₆H₅O₇•2H₂O as carbon and sodium sources,the carbon-coated Na_0.44MnO₂ (NMO/C) cathode material was prepared by one-step solid-state reaction. Its crystal structure and microstructure morphology were analyzed to explore the influence of Na₃C₆H₅O₇•2H₂O and Na₂CO₃ on the crystal structure of NMO/C.The coin cells assembled with NMO/C were constructed the cyclic voltammetry and first charge and discharge tests to investigate the electrochemical performance of NMO/C materials. The results indicate that the NMO/C materials has three-dimensional tunnel structure with the space group of Pbam, and its morphology is a long rod-like particle, which is covered uniformly with 2–3 nm carbon layer. When is used as the cathode material of sodium-ion half cells, the NMO/C cathode materials shows excellent long-term cycling stability and rate performance, with discharge specific capacity of 113.1 mAh•g⁻¹ for the first cycle and 74.1 mAh•g⁻¹ after 1 000 cycles at 0.5 C, which the capacity retention is 65.5%. The discharge specific capacities are 121.1, 117.4, 112.7, 105.6, and 98.3 mAh•g⁻¹ at at rates of 0.1, 0.2, 0.5, 1.0, 2.0 C, respectively. These improvements are attributed to the carbon-coating layer, which can not only effectively improve the electrical conductivity of the Na_0.44MnO₂, but also hinder its direct contact with the electrolyte and inhibit the dissolution of Mn³⁺. Therefore, the carbon-coated Na_0.44MnO₂ cathode material shows excellent electrochemical performance.