The influences of sodium sources on the structure evolution and electrochemical performances of layered-tunnel hybrid Na 0.6 MnO 2 cathode

Abstract Manganese (Mn) based oxide materials are regarded as promising cathodes for sodium ion batteries (SIBs) due to their high energy density, low-cost and environmental benignity. Here, we focus on the influences of various sodium sources on the structure diversity and electrochemical performances changes of layered-tunnel hybrid Na 0.6 MnO 2 cathode. The Na 0.6 MnO 2 cathodes were prepared by precipitation method followed by grinding with different sodium sources and annealing in air. The XRD results evidenced that the mass ratio of layered and tunnel components would be markedly influenced by sodium source. Electrochemical test results also demonstrate distinctive performances of Na 0.6 MnO 2 cathodes with various sodium sources. Na 0.6 MnO 2 cathode with Na 2 C 2 O 4 exhibited the best performances with 90 mAh g −1 retained after 100 cycles at 1.0C. Superior rate performance with average discharge capacities of 180, 159, 143, 126, 112 and 93 mAh g −1 at 0.1, 0.5, 1.0, 2.0, 4.0 and 8.0C was also observed. Furthermore, the EIS demonstrate that Na 0.6 MnO 2 cathode with Na 2 C 2 O 4 displayed smaller charge transfer and fast Na + diffusion rate, which indicated enhanced electrochemical reaction kinetics. The excellent electrochemical performance of Na 0.6 MnO 2 with Na 2 C 2 O 4 is mainly due to the appropriate proportion of layered-tunnel component and their synergistic effects, which are influenced by sodium sources.