Global demand for energy continues to rise dramatically and will do so into the foreseeable future. Energy storage technologies, such as Li-ion batteries, are considered the most promising for electric vehicles and renewable energy systems operating on intermittent energy sources such as wind and solar power. An in-depth introduction on secondary electrochemical energy storage technologies is presented with a special emphasis on the development of novel and effective improvements needed for existing Li-ion battery systems. The critical review of the relevant papers is focusing initially on Li -ion battery technology and its parameters followed by a detailed consideration of the electrode materials. Special focus is given to the anode materials, where tin-based alloy electrodes, prepared by electrodeposition and other methods, are described and discussed. Employing a range of different techniques based on electrode position, a number of novel binary and ternary alloys, namely SnCo, SnNi, SnFe, SnCoFe and SnNiFe, with a range of different compositions, structures and surface morphologies have been produced and tested in a model Li -ion cell as anodes to derive a Li-ion battery for improved future battery application. These results are discussed in detail and compared with results reported in relevant literature papers. The main focus was on the deposit performance as a negative electrode for Li-ion battery application. Their compositions, structures, phases and morphologies are given detailed consideration in relation to electrode performance. A key aspect reported is the investigation of these alloys with a view to identifying alloys with an appropriate Sn content, microstructure and surface morphology which indicate potential as a Li-ion electrode material. For each alloy system initially Hull cell and modified Hull cell experimentation was conducted to establish the boundary of the plating system in terms of quality of deposits and inform further in-depth experimentation and testing. A range of electrolyte combinations were initially studied to achieve suitable electrolytes operating under constant potential and pulse current deposition. The best performing SnCo alloy deposit as an electrode material was obtained by pulse plating at 100mA/cm2 with t on=O.Ols t off=0.49s resulting in a deposit which provided an initial 820mAh/g discharge capacity and a retained capacity after the 10th cycle of 420mAh/g. The SnNi system results indicate that constant potential deposition led to a retainable and stable discharge capacity of 765mAh/g over 10 lithiation-delithiation cycles. However, the theoretical capacity of this sample is 920mAh/g, which means that 17% of the theoretical capacity is inactive. The best SnFe deposit results indicate that constant potential deposition from a gluconate based electrolyte provided a maximum retainable discharge capacity of 500mAh/g after 10 lithiation-delithiation cycle. The best performing SnCoFe deposit as an electrode was obtained by pulse plating at 59mA/cm2 with t on=O.Ols t off=0.49s and it delivered an initial 550mAh/g discharge capacity with the retained capacity after the 10th cycle being 300mAh/g. A SnNiFe solid solution ternary system was electrode posited by pulse plating techniques at lOOmA/cm2 with ton=O.Ols toff=O.19s delivered an initial 700mAh/g discharge capacity which is only 3% less than the predicted theoretical capacity for the Sn content with retention of its capacity after the 10th cycle. This is the most promising result obtained within the framework of this study. It was also demonstrated that increasing the substrate roughness prior to deposition leads to a desirable large surface area per unit volume and thus supports the theoretical capacity of the samples being achieved. This result ultimately proved that a large surface area per unit volume morphology is the key factor to improve the Sn alloys cycle life and discharge capacity performance. The previously mentioned results are generally better than the conventional carbon discharge capacity (250-400mAh/g), and all of these alloys have a distinct potential for development as new electrode materials for Li-ion battery application.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:676483 |
| Date | January 2014 |
| Creators | Lak, Gyorgy B. |
| Publisher | Glasgow Caledonian University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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