Preparation Of Manganese Based Electrode Materials For Li-ion Batteries

Li-ion batteries are devices that associated with energy storage and conversion. With the increasing pressure of the depletion of fossil fuels and the climate change, human society has to cut down the use of traditional energy sources and move towards sustainable and renewable resources. This promotes the development of new technologies associated with energy storage and conversion. In this thesis, manganese based electrode materials with different crystal structures and morphologies were synthesized via template method and grinding method and the electrochemical properties of the materials were studied.With filter paper as sacrificed template and ethanol as combustion agent, spinel type cathode materials LiMn2O4and LiNio.5Mn1.5O4for Li-ion batteries were prepared. LiMn2O4can retain92%of its highest capacity after200cycles at the current density of100mA/g, and the coulombic efficiency always keeps above99%during the cycling process. After doping of Ni, high voltage spinel LiNio.5Mn1.5O4with a4.7V discharge plateau was also obtained. Layered LiCoO2and LiCo1-xMnxO2(x=0.025,0.05,0.1and0.15) were also synthesized by this method. Although LiCoO2has a high initial discharge capacity, it fades fast during the cycling process and can only retain74.4%of its initial capacity after80cycles. But the capacity retention can be improved to86.6%by doping5mol%Mn.With the rod like tartrate manganese as template, porous rod like Mn2O3, MnO/C anode materials and LiMn2O4cathode material were prepared. The cycling and rate performances of MnO/C are obviously superior to Mn2O3. For LiMn2O4cathode material, its capacity can still retain95.7%after50cycles, and from the2nd cycle on, the coulombic efficiency can keep above99%.With LiAc·2H2O and Mn(Ac)2·4H2O as reagents, ethanol as dispersion agent, C4H6O6as additive, spinel LiMn2O4cathode material were prepared using grinding and annealing method. A complicated Li-Mn-Ac precursor was obtained without the addition of C4H6O6. But after the addition of C4H6O6, a precursor with a mixture of tartrate manganese and tartrate lithium were obtained. Without the addition of C4H6O6, the final products LiMn2O4obtained after were irregular and in the range of micrometer. But for LiMn2O4obtained by the addition of C4H6O6during the grinding process, porous spherical morphology was finally gained. The addition of C4H6O6remarkably improved the electrochemical properties of the final products.