Investigation into the Synthesis and Characterisation of Hematite Nanomaterials for the Fabrication of Novel Composite Anodes for Potential Use in Lithium-Ion Batteries

Triana Wulandari

Today the world is experiencing climate change and a global warming crisis. Therefore, the world needs to embrace renewable and sustainable green energy-based technologies to replace current fossil fuel-based energy systems. However, harvesting renewable energy from intermittent sources like solar and wind needs to be integrated with large-scale energy storage systems to ensure a consistent energy supply network. Thus, rechargeable battery-based energy storage systems are an effective method for first storing harvested energy and then releasing electrical energy to the supply network when needed. Importantly, lithium ion (Li-ion) batteries have high energy and power densities and long-life cycles, which also makes them candidates for large scale energy storage systems. But operational issues such as aging mechanisms, active material degradation processes and safety concerns persist. Studies have shown battery performance and longevity are affected by factors like types of materials used to manufacture the anode and cathode, operating temperature, depth of discharge, charge/discharge current rates, periods between full-charge cycles. Li-ion batteries have traditionally used graphite anodes. Unfortunately, graphite anodes cannot meet all the physiochemical and electrochemical requirements needed to meet the increasing demand for high energy density storage systems. The present work investigates developing novel nanomaterial hematite (α-Fe2O3) based anode materials for Li-ion batteries. The work focused on three research outcomes. The first outcome delivered an extensive overview of the current state of research and progress towards developing the next generation of high-performance Li-ion ion batteries. Importantly, current short-coming associated with Li-ion batteries and the need for developing new anode materials for the next generation of high-performance Li-ion ion batteries was thoroughly discussed. The next research outcome focused on investigating novel methods for synthesizing hematite nanomaterials suitable for anode fabrication. The three methods investigated were: 1) a micro-emulsion via the Reverse Micelle method; 2) direct chemical precipitation, and 3) sonochemical. Advanced characterisation studies were carried to determine the physiochemical properties of the hematite nanopowders produced by each method. From these studies, hematite nanopowders produced by sonochemical means was selected first for anode fabrication. Theoretically, hematite has a specific capacity value of 1004 mAhg-1, but due to two shortcomings (capacity fading and large volumetric changes during lithiation/de-lithiation over time), this value is not achieved. Thus, the third research outcome involved the fabrication of composite hematite and carbon black anodes produced by electrophoretic deposition. The composite was developed to mediate the effects of the two abovementioned shortcomings. Thus, providing an attractive alternative to currently used graphite-based anodes. Cyclic voltammetry, Galvanostatic charge−discharge, and impedance studies were used to determine electrochemical properties of the novel composite anode materials. The studies found that a hematite/10% carbon black composite anode had a high operational specific capacity value of 630 mAh g-1, which is superior to currently used graphite anodes that only have a theoretical specific capacity value of 372 mAh g-1. Interestingly, the study also found the larger pseudo-capacitance exhibited by the hematite/20% carbon black anode could also be used to develop new types of capacitors. Thus, the present research has demonstrated that a hematite/10% carbon black anode has greater specific capacity value and the potential to replace currently used graphite anodes.

Investigation into the Synthesis and Characterisation of Hematite Nanomaterials for the Fabrication of Novel Composite Anodes for Potential Use in Lithium-Ion Batteries

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