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Continuous hydrothermal flow synthesis of lithium ion battery materials

There are a number of ways to improve the capacity of rechargeable batteries as suggested in the literature; carbon coating and reducing the particle size of the active material appear to be the most effective. In this work, the synthesis of pure phase LiFePO₄ nanoparticles was carried out directly in one step using the continuous hydrothermal flow synthesis (CHFS) system. Conventional synthesis methods require many steps and longer duration to obtain this cathode material. Microscopic data confirmed that the particles were successfully covered with an even carbon coating in situ where fructose was used. Through the use of the CHFS pilot plant, larger batches of the samples were made to allow thorough characterisation and electrochemical analysis. Coin cells were assembled from electrode sheets with the samples synthesised as the active material. The data collected from carbon coated LiFePO₄ cells showed good performance in terms of high C rate cycling and the specific capacity the cells provided. The results were comparable to those seen in the literature and amongst the highest of LiFePO₄ produced from a CHFS method. The doping of LiFePO₄ with manganese was successful as confirmed by various analysis techniques but it did not appear to have improved the electrochemical operation of LiFePO₄. However, upon certain doping levels the energy density of the material was approaching the theoretical value. The CHFS system was also used in an attempt to synthesise cathode materials optimised for electrochemical performance. For example, reaction conditions were tailored to produce samples with reduced particle sizes and samples intimately mixed with conductive carbon in situ. Further work will be to optimise the material ratio for electrodes and increase the amount of active material to be used. Also, to investigate fully how the morphology and thickness of an electrode can affect the performance of the cell.
Date January 2014
CreatorsWu, O. Y.
PublisherUniversity College London (University of London)
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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