A Study Of Components For Lithium And Sodium Batteries And Other Storage Devices

Abstract

An investigation of electrochemical storage device materials has been undertaken in four parts. The bulk and interfacial resistance of Na+ beta-alumina tubes were separated using a galvanostatic charge-discharge method. Sodium silicide was characterized to better understand its synthesis. BiMn2O5 was produced using a sol-gel method and tested for pseudocapacity. Different lithium ion anode and cathode materials were deposited using a new electrophoretic deposition method. A novel galvanostatic charge-discharge method was developed for the determination of bulk and interface resistance in Na+ beta-alumina solid electrolytes [BASE]. Dense and duplex BASE tubes were tested by varying the exposed surface area. The results of dense BASE tube pairs were used to determine the bulk and interfacial resistance components, while duplex BASE tubes were tested to determine the reduction in interfacial resistance. It was found that duplex tubes had reduced the interfacial resistance by 75%, when compared to a uniformly dense electrolyte. Sodium silicide was characterized using various methods to better understand the phase and the Na-Si phase diagram. EMF experiments using Na+ BASE tubes was used to determine the activity in the silicon rich region of the phase diagram, which showed a sodium activity of 0.5 at 550°C. TGA/DSC was used to determine phase transformation temperatures, as well as the heat of formation for NaSi, which was recorded to be below 1 kJ mol-1. A sol-gel precipitation method was used to produce fine BiMn2O5 powders used for supercapacitors. The powders resulting from a consistent method were tested for pseudocapacitance using bulk and thin film electrodes. Bulk electrodes had a gravimetric capacitance of 10 F g-1, while thin film electrodes only reached 2.6 F g-1. Lithium ion battery anode (Li4Ti5O12) and cathode (LiFePO4, LiMn2O4, LiMn1.5Ni0.5O4) materials were electrophoretically deposited with the assistance of PAZO-Na and CMC-Na. Cathodes were successfully deposited on aluminium substrates, and were tested in the potential window 2 – 4.3 V. The LiFePO4 cathodes showed capacity of 146.7 mAh g-1 at C/10, while showing capacity retention of 103% after 50 cycles.