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The composition and production of cathode materials used in aqueous lithium-ion batteries

Walker, Mitchell (2018) The composition and production of cathode materials used in aqueous lithium-ion batteries. Honours thesis, Murdoch University.

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Abstract

Renewable sources of energy are becoming a more preferred energy source as the environmental impact of non-renewable fossil fuels becomes apparent. Lithium-ion batteries have been an attractive option for portable reliable energy sources as they possess high energy density, reliability and show little self-discharge. Most lithium-ion batteries utilise an extremely toxic electrolyte composed of a mixture of organic compounds. Aqueous batteries have been a promising research topic in recent times, as they can provide energy storage without the dangerous environmental and health impacts of traditional lithium-ion batteries.

A well-studied cathode material suitable in aqueous electrolytes is LiMn2O4. This paper aims to examine the electrochemical effects of nickel and cobalt doping in LiMn2O4 and the effect of synthesis temperature on the crystal structure. To accomplish this, LiMn2O4, LiMn1.8 Co0.2O4 and LiNi0.2Mn1.8 O4 were synthesised using a sol-gel method. Each sample was calcined at 750, 850 and 950 °C before being examined by XRD analysis, cyclic voltammetry scan and a charge-discharge test.

The results of this study show the calcination temperature has a large impact on the structure and electrochemical performance of the battery. There was no clear trend in reversibility with the LiMn2O4, however, Li Co0.2Mn1.8O4 demonstrated increased reversibility with increasing calcination temperature, and in general, showed superior reversibility compared to LiMn2O4. Introduction of nickel showed no significant change in reversibility compared to the undoped version, however reversibility of LiMn1.8 Ni0.2O4 decreased with increased calcination temperature.

The discharge capacity test showed 750 °C to be the optimal temperature for synthesis of LiMn2O4 and LiCo0.2Mn1.8O4 whilst 950 °C was the best performing nickel doped variant. Overall, an introduction of cobalt was observed to increase discharge capacity by 5.0 % (0.589 mAh compared to 0.560 mAh), whilst nickel reduced discharge performance by 2.8 % (0.544 mAh vs 0.590 mAh).

Item Type: Thesis (Honours)
Supervisor(s): Aleksandar, Nikoloski, Issa, Touma and Singh, Pritam
URI: http://researchrepository.murdoch.edu.au/id/eprint/44799
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