Synthesis and characterisation of LiV₃O₈ cathode and Li₄Ti₅O₁₂ anode materials for lithium-ion batteries (declaration)

Lithium ion (Li-ion) batteries become the most potential energy source for mobile electronic devices due to their balance of high energy density, cyclability and power density compared to other electrochemical energy carriers. There is a great attention in the automotive industry to use Li-ion batteries as ‘green energy’ but improvement in power density is very vital. Among the method to improve power density is to use electrochemically active material with a higher electrochemical performance such as high voltage and high specific capacity. In this present study, lithium vanadate, LiV₃O₈ cathode with a layered crystal structure has been studied as potential candidate for active cathode material in Li-ion batteries due to its good structural stability, high specific capacity and good safety features. Several methods have been approached to synthesis layered structure of LiV₃O₈. The conventional solid state, sol-gel and reflux methods have been selected to synthesis LiV₃O₈. LiV₃O₈ with the best characteristics will be chosen and heated at temperatures 300, 350, 400, 450, 500 and 550 °C to find the best optimized temperature. In this study, parent composition of LiV₃O₈ has been doped with cobalt, Co and nickel, Ni atoms of 0.1 < x < 0.5 range to produce LiV3-x(NiCo)xO8 cathode. These compositions were characterised by using X-ray diffraction (XRD), thermal gravimetric analyser (TGA), differential thermal analyser (DTA), brunner emmet- teller (BET), scanning electron microscope (SEM), cyclic voltammetry (CV), charge- discharge (CD) and electrochemical impedance spectroscopy analyser (EIS). The structural and electrochemical of the prepared samples were optimised by using solid state method and at 500 °C heating temperature. All the XRD patterns of cathode materials could be indexed with the layered structure and the space group of P21/m. The parent composition shows the specific capacity of 172, 157 and 112 mAh g-1 for the 1st, 2nd and 3rd cycles, respectively. The charge-discharge results show that LiV3-x (NiCo) xO8, x = 0.5 is the best composition with specific capacity of 265 mAh g-1, which is about 89.29 % higher than commercial LiCoO2. Currently, graphite is widely used as the anode material in commercial lithium-ion batteries but presents poor rate capability, bad cycling performance and serious safety issues. It is very crucial to develop alternative anodes with impressive electrochemical performances for energy storage. As a potential anode material, spinel Li₄Ti₅O₁₂ has attracted great interest for Li-ion batteries because of its good safety, cyclability and near-zero volume change during the charge/discharge process. In this work, the anode Li4Ti5O12 have been successfully fabricated using a planetary ball milling method at 2, 4, 6 and 8 hours milling time and heating at 800°C in air for 10 hours and then slow cooled to room temperature. All the XRD patterns could be indexed with the cubic spinel structure and the space group of Fd-3m. The specific capacity of Li₄Ti₅O₁₂ is 162, 159 and 155mAh g-1 for the 1st, 2nd and 3rd cycles. The cycle life for 40 cycles shows a very stable cycling and the capacity fading only less than 5 %. These results remarked the LiV3O8 cathode and Li₄Ti₅O₁₂ anode can be considered as potential alternative materials in Li-ion battery application.