| MnO2has attracted great interest as a cathode material for lithium ion batteries due to its low cost, high specific capacity and environmental friendliness. MnO2nanorods were prepared by a hydrothermal method. For preparing MnO2/graphene composite, MnO2nanorod was put into graphite oxide (GO) solution with stirring untile the water evaporated at80℃. After the MnO2nanorods attached on the GO, the MnO2/GO was calcined in the air for2h to obtain MnO2/graphene composite. Graphene is a good conductive material, which can improve the conductivity of MnO2. The first discharge capacities of MnO2/graphene were240mAh g-1and136mAh g-1at0.1C and1C (where1C=308mA g-1). The capacity reveals almost no capacity fading to the100th cycle with a capacity of158.3mAh g-1, indicating the good cycling stability of MnO2/graphene. Even though the discharge/charge current density is increased to the rate of1.5C, the capacity of MnO2/graphene can be retained at68.2mAh g-1.This work is to develop a simple and effect template method to synthesize spinel LiMn2O4nanorods. To further improve cycling performance, the LiAlxMn2-xO4nanorods were synthesized. By comparison, LiAlo.05Mn1.95O4has the best electrochemical performance. A the current density of5C (1C=148mA g-1), the capacity of LiAl0.05Mn1.95O4is83.6mAh g-1. After250cycles at the current density of0.2C, the capacity can be maintained at101.4mAh g-1, the capacity retention ratio is86%. It has a unique one-dimensional rod structure, reducing the lithium ion diffusion distance which is conducive to the rapid extraction and insertion of lithium ions. A part of Mn is replaced by Al, and the average valence of Mn is increased to reduce the dissolution of Mn. Meanwhile, the Jahn-Teller effect is suppressed which can improve the cycle performance and rate properties of the material.MnO/graphene composites were prepared by calcining MnO2nanorods and graphite oxide as precursor under Ar gas. As the anode mnaterial for lithium ion batteries, the first discharge capacity of MnO/graphene composites is1144mAh g-1at the current density of50mA g-1. The MnO/graphene composite deliveres a high initial charge capacity up to747mAh g-1and a stable capacity of705.8mAh g-1after100cycles at the current density of100mA g-1, which is close to the theoretical capacity of MnO (755mAh g-1). The capacity retention ratio is94.5%. When the current density is up to800mA g-1,the capacity of MnO/graphene is299mAh g-1.MnO/N-graphene composite was prepared by hydrothermal/thermal reduction and was used as the anode material for lithium ion batteries. Nitrogen-doped graphene is an excellent matrix to host active nanomaterials for energy applications due to its high conductivity, large surface area. And it can provide active sites to improve the cycling performance of the electrode. By comparison, the best content of graphene is9%. The MnO/N-graphene composite deliveres a high initial discharge capacity up to1104mAh g-1and a stable capacity of689mAh g-1after100cycles at the current density of100mA g-1. The capacity retention ratio is95.7%. When the current density is up to1600mA g-1,the capacity of MnO/graphene is285.4mAh g-1. |
