SURPRISING IMPROVEMENTS IN LITHIUM ION AND SODIUM ION BATTERY CYCLE LIFE

Abstract

Lithium ion battery research attracts much attention because lithium ion batteries have such extensive applications. Sodium ion batteries are an emerging field because of the sustainability of Na vs Li. However, issues regarding electrode and electrolyte degradation during cycling have hindered battery performance in both these technologies. In this thesis, thermoelectrochemical activation and ball milling methods were applied to improve the electrochemical performance of inactive CoO in sodium ion batteries. Results show that each method can increase the specific capacity and the combination of both methods can lead to a higher specific capacity and a stable cycling performance. CO2 has been shown to have great benefits on the cycle life of silicon alloy anodes. In this thesis, a new method was developed to measure CO2 concentration in electrolyte quantitatively and accurately by FITR. It was shown that the CO2 solubility in 1 M Li+ EC/DEC (1:2 v/v) solutions depends significantly on the salt anion and in a complicated manner. CO2 scavengers like DETA can increase the CO2 solubility effectively at a low concentration, but cause phase separation at higher concentrations.