Preparation And Electrochemical Performance Of Mn/Co Oxides Anodes For Lithium Ion Batteries

The lithium ion battery ?LIB?, as a widely used energy storage device, has the characteristics of high reversible capacity, good safety and long cycling performance. The prevailingly used graphite anode materials has a low capacity of 372 mA h g"1, which limits the development of LIB. As a possible anode candidate, the transition metal oxides ?TMOs? show high theoretical capacity and low discharge potential versus Li/Li+. However, some problems, such as large volume expansion and severe particle aggregation, need to be overcome. Considering the merits of the carbon materials, such as high conductivity and controllable structure, my works have focused on designing and synthesizing kinds of TMOs/C hybrids as the LIBs anode material. Moreover, we have established a novel and solvent-free synthesis of superior performance TMOs/C anode derived from binary metal oxides. Specifically, the works include the following parts:?1? The MnOx/C composite materials are synthesized via in-situ growth of crystalline ZIF-8 on a binary metal oxide ZnMnO₃ approach followed by carbon-thermal reduction. ZnMnO₃ is chosen together with imidazole to direct ZIF-8 growing around manganese oxides according to the theory of hard and soft acids and bases. The MnOx/C electrodes from different precursors exhibit good electrochemical performance. Especially, the one using 3D MnO2 as precursor shows 1201 mA h g-1 at the current of 0.2 A g-1 after 240 cycles.?2? The Co₃O₄/C composite materials are prepared by the same method of synthesis MnOx/C. ZnCo₂O₄ as the precursor provides Zn2+for the formation of ZIF-8. Followed carbon-thermal reduction and an essential oxidation process, the Co₃O₄/C electrode is fabricated as well. Used as an anode, the materials display a specific capacity of 904 mA h g-1 at the current density of 0.2 A g-1.?3? N-doped carbon composite materials ?Co₃O₄/C? are synthesized through a two-step method:synthetic process of ZnCo₂O₄/GO and coating process of dopamine. The Co₃O₄/C composite exhibits a very high specific capacity of 1040 mA h g-1 at the current density of 0.2 A g-1 with no obvious capacity fading.