Preparation And Electrochemical Properties Of Sodium Permanganate Cathode Materials For Sodium-ion Batteries

With the rapid development of the energy storage, the problem of the depletion for lithium resources will be faced in the near future. Sodium has many advantages like high abundance and low cost. If the electrochemical properties of the sodium-ion batteries can reach the same level to the lithium-ion batteries, it will have a good prospect in application. However, the radius of the sodium ion is much larger than lithium. It means that the lattice structure will have a huge volume change and collapse while cycling. Fortunately, sodium permanganate material can form large layered distance or channel which can accelerate sodium ions intercalation/de-intercalation. What's more, all the elements manganese, sodium and oxygen of the material are all non-toxic, making it feasible usable application for large scale.In this paper, sodium permanganate material is the main object. Two kinds of new materials were synthesized by a simple liquid phase reaction. Na0.31MnO1.9 is for the layered structure and Na0.53MnO2.13 is for the pore structure.Romanechite-structured Na0.31MnO1.9 material is tunnel nanofiber and P2-typed Na0.53MnO2.13 is layered nanoparticle. They are all prepared through combining chelator-assisted precipitation method and high-temperature calcination processes. Manganese acetate, ethylene diamine tetra-acetic acid and sodium hydroxide are as the raw materials. After adjusting the feed ratio of reactants, pH value of the reaction solution, the calcination temperature, the calcination time and the other conditions, two different products were obtained. Electrochemical tests showed that, in a voltage range of 2-4.5 V, pore structured Na0.31MnO1.9 can deliver a reversible capacity more than 100 mAhg-1 (theoretical capacity= 104.4 mAhg-1). And about the layered-structure Nao.53Mn02.13, when the voltage range is 2-4.3V, it can deliver a reversible capacity about 135.7 mAhg-1 which was very closer to the theoretical capacity. The two materials both have good cycling performances and superior rate performances. More interestingly, Na0.31MnO1.9 nanofibers and Nao.53MnO2.13 nanoparticles have a very good electrochemical performance of fast charging and slow discharging, which will be very essential for practical application. Meanwhile, the lattice diffusion process of the cathode materials were also investigated in detail through the technologies of electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT) and ex-situ XRD.