High-voltage LiNi 0.5 Mn 1.5 O 4 with a spinel structure is considered as important cathode materials for high-energy density Li-ion batteries (LIBs). In this study, we investigate the size, structure, and the electrochemical performance of LiNi 0.5 Mn 1.5 O 4 electrodes prepared by using two different-sized Mn 3 O 4 nanocrystal precursors under different calcination conditions. As the calcination temperature rises, the particle sizes of the acquired LiNi 0.5 Mn 1.5 O 4 cathode materials can vary from ~ 100 nm to ~ 1 µm, and the morphology changes from nano round shape to truncated octahedral shape. The content of Mn 3+ is closely related to the calcination temperature and is affected by the size of Mn precursor. It is found that the LiNi 0.5 Mn 1.5 O 4 sample prepared by using 50-nm-sized Mn 3 O 4 nanocrystals under a calcination temperature of 800 C exhibits good cycling performance with a capacity retention ratio of 96.1% at 1 C after 200 cycles, while the LiNi 0.5 Mn 1.5 O 4 sample prepared by using 7-nm-sized Mn 3 O 4 nanocrystals under a calcination temperature of 800 °C shows an excellent rate performance with a capacity retention ratio of 98% after 500 cycles at 10 C. The results show that the size of Mn 3 O 4 precursor is an important parameter that governs the final size and electrochemical performances of LiNi 0.5 Mn 1.5 O 4 cathode materials.
Wenjin Xu,Guangxu Zhang,Hanwei Chen,Guomeng Zhang,Yang Han,Yichuan Chang,Peng Gong
Two series of Mn/beta and Mn/ZSM-5 catalysts were prepared to study the influence of how different Mn precursors, introduced to the respective parent zeolites by wet impregnation, affected the selective catalytic reduction (SCR) of NO by NH 3 across a low reaction temperature window of 50–350 °C. In this study, the catalysts were characterized using N 2 adsorption/desorption, X-ray diffraction, X-ray fluorescence, H 2 temperature-programmed reduction, NH 3 temperature-programmed desorption and X-ray photoelectron spectroscopy. As the manganese chloride precursor only partially decomposed this primarily resulted in the formation of MnCl 2 in addition to the presence of low levels of crystalline Mn 3 O 4 , which resulted in poor catalytic performance. However, the manganese nitrate precursor formed crystalline MnO 2 as the major phase in addition to a minor presence of unconverted Mn-nitrate. Furthermore, manganese acetate resulted principally in a mixture of amorphous Mn 2 O 3 and MnO 2 , and crystalline Mn 3 O 4 . From all the catalysts screened, the test performance data showed Mn/beta-Ac to exhibit the highest NO conversion (97.5%) at 240 °C, which remained >90% across a temperature window of 220–350 °C. The excellent catalytic performance was ascribed to the enrichment of highly dispersed MnO x (Mn 2 O 3 and MnO 2 ) species that act as the active phase in the NH 3 -SCR process. Furthermore, together with a suitable amount of weakly acidic centers, higher concentration of surface manganese and a greater presence of surface labile oxygen groups, SCR performance was collectively enhanced at low temperature.
Manganese oxides with desired structure are controllably obtained through annealing MnCO 3 precursors with required structures. The structures of MnCO 3 precursors are determined by a “mesocrystal formation” process in an ionic liquid system of a choline chloride/urea (CU) mixture. Without addition of surfactants, only CU solvent and manganese chloride are needed in the reaction system, in which the CU acts as reaction medium as well as control agent for particle growth. A shape transformation of MnCO 3 particles from well-defined rhombohedral mesocrystals to ellipsoidal polycrystal ensembles, and to nanoparticulate aggregates is observed when heating the reaction system for 4 h at 120, 150, and 180 °C, respectively. With a longer aging time at 120 °C, etching and disassembly of MnCO 3 mesocrystals happened. The correlation between the microstructure and the underlying formation mechanism is highlighted. Porous and nanowire-like MnO x nanostructures are obtained through a facile thermal conversion process from the diverse MnCO 3 precursors, which are demonstrated as effective and efficient adsorbents to remove organic waste (e.g. Congo red) from water. Significantly, the nanowire-like MnO x nanostructures obtained by annealing the MnCO 3 mesocrystals at 300 °C for 4 h can remove about 95% Congo red in waste water at room temperature in only one minute, which is superior to the reported hierarchical hollow nanostructured MnO 2 .
危险品化学品经营许可证（带存储）