Study On The Synthesis Of Transition Metal Oxide Multi-shelled Hollow Microspheres And Their Energy Storage Properties

Energy shortage and environmental pollution have become essential problems for the global world nowadays, which can be remitted or even settled down by developing effective and environment-friendly energy and energy storage systems. Among various kinds of energy storage systems, lithium-ion batteries (LIBs) and supercapacitors (SCs) have drawn great attention due to their obvious advantages. However, the further development and wider application of LIBs and SCs have been suffered from a series of problems, such as low accessible energy density, poor cycling stability and so forth. In this thesis, by starting from the design and controlled synthesis of hollow micro-/nanostructures, we develop a series of multi-shelled metal oxide hollow micro/nanostructures as electrode materials for LIBs and SCs, trying to solve the current remained problems and further improve their performance. Main results are obtained and listed below:1. Although Co3O4 as anode materials for LIBs can greatly improve the specific capacity, the large volume-expansion can result in severe damage to the structure, leading to a poor cycling performance, thus largely hinders its practical use in LIBs. To solve these problems, we prepare multi-shelled Co3O4 hollow microspheres with uniform size and high yield and purity by enhancing the precursor-adsorption of carbonaceous microsphere (CMS) templates through a series of methods. When used as the anode material for LIBs, they exhibit high specific capacity, long cycle life, and superior rate capability (1615.8 mAh/g remained at the 30th cycle for the triple-shelled at a current density of 50 mA/g).2. Using V2O5 to replace the current commercial cathode materials can further improve the total capacity of the full LIBs. However, their poor structural stability induced by irreversible phase transitions upon deep discharge limited their applications in LIBs. Here, we put forward and verify a new concept of anions-adsorption by negatively-charged CMS templates through deeply exploiting the mechanism. And followed with a Trojan catalytic combustion process to remove the templates, hollow V2O5 microspheres with multiple shells or cavities are developed. Besides, the shell number, shell thickness, porosity and crystallinity are accurately controlled. Benefited from the large surface area, short electron/ion transport length, high structural stability, LIBs based on multi-shelled V2O5 hollow microspheres cathode material show new-record high capacity, stable cycling performance and good rate capability (at a current density of 1000 mA/g,447 and 402 mAh/g was achieved for the first and the 100th cycle, respectively). This study opens a new insight into the development of next-generation LIBs with high energy density and power density.3. The energy density of LIBs depends on both the specific capacity and the voltage range.Cr2O3 has been considered as a promising anode material of LIBs for a long time, owning to its higher theoretical capacity and lower plateaus than other transition-metal oxides such as Co3O4 and Fe2O3. However, the actual application of Cr2O3 still suffers from poor cycling performance caused by the huge volume variation, pulverization, electrical contact loss during the lithium insertion/extraction processes. To solve these problems, we synthesize single-, double-, triple-, quadruple-, quintuple-shelled Cr2O3 hollow microspheres by adjusting the size of the templates as well as the adsorption duration. As anode materials for LIBs, these multi-shelled Cr2O3 hollow microspheres show the best LIB performance to date.4. Multi-shelled hollow structures can not only be used in LIBs, but also show great application advantages in Supercapacitors (SCs). Here, we prepared multi-shelled Mn2O3 hollow microspheres, and accurately controlled their structural parameters such as shell number, shell thickness and grain size. Profited from the structural superiorities of multi-shelled hollow structures, the problems of Mn2O3 such as low specific surface area, multi-shelled hollow structures, the problems of Mn2O3 such as low specific surface area, poor electron/ion transport ability, and partial dissolution in electrolyte are well solved. When used as the electrode materials for SCs, the specific capacity, cycling performance and the rate capability of SCs are all greatly improved (1651 F/g at a current density of 0.5 A/g for the triple-shelled).