Developments of Low Cost Aqueous Sodium Ion Batteries with Prussian Blue Analogue Positive Electrodes for Solar Energy Storage Applications

Abstract

In this thesis, different aqueous sodium ion batteries are presented with various combinations of positive electrode, negative electrode and electrolyte, whereas the target application is the solar energy storage. Several Prussian blue analogues (PBAs) with multiple transition metal substitutions are utilized as positive electrodes, while diverse classes of redox active materials, namely functionalized carbons, vanadium based polyoxometalates, metal oxides, metal phosphates etc. are screened for negative electrodes. Herein, low-cost stainless steel current collectors are utilized, while optimized corrosion protective coatings are applied. The sodium ion prototype cells and devices with multiple electrode couples are assembled in both flooded and starved electrolyte configurations. The exploitation of hydrogels as electrolyte media is vividly emphasized in this thesis. However, all the developed prototype cells/devices are laboratory tested through specific capacity, Faradaic efficiency, rate capability, energy density, power density and cycle life at a wide range of working temperatures. Moreover, the prototype devices are also performance tested through the custom-built solar charging module as part of the feasibility assessments for solar energy storage applications. However, this thesis comprises eight chapters, and brief descriptions of each chapter are following. Chapter 1 elaborates the basic concepts of battery applications in renewable energy storage sectors. This chapter starts with the fundamental ideas of energy storage devices, namely batteries and supercapacitors, while their significances in our daily life are greatly discussed. The limitations of present battery technologies for solar energy storage are addressed, and the lacuna could be filled by the introduction of aqueous sodium ion batteries. The middle part of this chapter deals with the sodium ion electrochemistry and relevant active material screening. However, this chapter culminates with the wise selection of PBAs as positive electrode mat