Abstract:
Taking MnCO
3 as manganese source and Na
3C
6H
5O
7•2H
2O as carbon and sodium sources,the carbon-coated Na
0.44MnO
2 (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 Na
3C
6H
5O
7•2H
2O and Na
2CO
3 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
0.44MnO
2, but also hinder its direct contact with the electrolyte and inhibit the dissolution of Mn
3+. Therefore, the carbon-coated Na
0.44MnO
2 cathode material shows excellent electrochemical performance.