This PhD work is dedicated to the discovery and study of new cathode materials for lithium-ion batteries. To obtain new materials, a well-known strategy based on ion-exchanging alkali metals within stable crystalline frameworks was used. Ion-exchange procedures between sodium and lithium ions were performed on known sodiated materials, NaMnTiO4 with the Na0.44MnO2 structure and NaFeTiO4 and Na2Fe3-xSn2xSb1-xO8 (0 ≤ x ≤ 1) with the calcium-ferrite structure. A combination of Energy-Dispersive X-ray Spectroscopy (EDS), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), X-ray (XRD) and Neutron (NPD) diffractions was used to determine the crystal structure of the samples obtained via ion-exchange and confirmed that LiMnTiO4 and LiFeTiO4 and Li2Fe3-xSn2xSb1-xO8 (0 ≤ x ≤ 1) were obtained with a 1:1 ion-exchange between sodium and lithium. LiMnTiO4 has the orthorhombic Pbam space group, with a = 9.074(5), b = 24.97(1) and c = 2.899(2) Å. The shapes and dimensions of the channels are modified compared to NaMnTiO4, with displaced alkali metal positions and occupancies. LiMnTiO4 was cycled vs Li and up to 0.89 lithium ions can be reversibly inserted into the structure, with a discharge capacity of 137 mAh/g after 20 cycles at C/20 and room temperature. At 60°C, all the lithium is removed at the end of the first charge at C/20, with subsequent cycles showing reversible insertion of 1.06 Li-ions when cycled between 1.5 and 4.6 V. The electrochemistry of calcium-ferrite LiFeTiO4 and Li2Fe3SbO8 was investigated in half cells versus lithium and up to 0.63 and 1.35 lithium ions can be reversibly inserted into the structure after 50 cycles at a C/5 rate, respectively. LiFeTiO4 showed good cyclability with no capacity fade observed after the second cycle while Li2Fe3SbO8 exhibited a constant capacity fade with a 60 % capacity retention after the 50th cycle. Doping Li2Fe3SbO8 with tin reduces the capacity. However, the capacity retention is significantly enhanced. For Li2Fe2.5Sb0.5SnO8 after 20 cycles at C/5, the capacity is stable and comparable with that observed for Li2Fe3SbO8 after the same number of cycles. Using ion-exchange procedures has allowed new metastable materials to be obtained which have the potential to be used as cathodes in lithium-ion batteries. Doping these families of materials with different atoms has been shown to improve their electrochemical performance. Ex situ XRD was used to demonstrate that the original structures of LiMnTiO4, LiFeTiO4 and Li2Fe3SbO8 are retained during cycling. The volume change observed for Li2Fe3SbO8 upon delithiation was particularly noteworthy with a small decrease of 0.9 % at the end of charge when cycled at C/100 and room temperature, indicating structural stability upon lithium insertion/de-insertion.

Electrochemical behavior of electrolytic manganese dioxide (EMD), chemically prepared battery grade manganese dioxide (BGM), titanium dioxide (TiO2), lithium iron phosphate (LiFePO4) and lithium manganese phosphate (LiMnPO4) in aqueous lithium hydroxide electrolyte has been investigated. These materials are commonly used as cathodes in non-aqueous electrolyte lithium batteries. The main aim of the work was to determine how the electroreduction/oxidation behavior of these materials in aqueous LiOH compares with that reported in the literature in non-aqueous electrolytes in connection with lithium batteries. An objective was to establish whether these materials could also be used to develop other battery systems using aqueous LiOH as electrolyte. The electrochemical characteristics of the above materials were investigated by subjecting them to slow scan cyclic voltammetry and determining the charge/discharge characteristics of Zn/cathode material-aqueous LiOH batteries. The products of electroreduction/oxidation were characterized by physical techniques using X-ray diffraction (XRD), scanning electron micrography (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), Thermogravimetric analysis (TG) and infra-red spectrometry (IR). The reduction of ã-MnO2 (EMD) in aqueous lithium hydroxide electrolyte is found to result in intercalation of Li+ into the host structure of ã-MnO2. The process was found to be reversible for many cycles. This is similar to what is known to occur for ã-MnO2 in non-aqueous electrolytes. The mechanism, however, differs from that for reduction/oxidation of ã-MnO2 in aqueous potassium hydroxide electrolyte. KOH electrolyte is used in the state-of-art aqueous alkaline Zn/MnO2 batteries. Alkaline batteries based on aqueous KOH as the electrolyte rely upon a mechanism other than K+ intercalation into MnO2. This mechanism is not reversible. This is explained in terms of the relative ionic sizes of Li+ and K+. The lithium-intercalated MnO2 lattice is stable because Li+ and Mn4+ are of approximately the same size and hence Li+ is accommodated nicely into the host lattice of MnO2. The K+ ion which has almost double the size of Li+ cannot be appropriately accommodated into the host structure and hence the K+ -intercalated MnO2 phase is not stable. Chemically prepared battery grade MnO2 (BGM) is found to undergo electroreduction/oxidation in aqueous LiOH via the same Li+ intercalation mechanism as for the EMD. While the Zn/BGM- aqueous LiOH cell discharges at a voltage higher than that for the Zn/EMD- aqueous LiOH cell under similar conditions, the rechargeability and the material utilization of the BGM cell is poorer. The cathodic behavior of TiO2 (anatase phase) in the presence of aqueous LiOH is not reversible. In addition to LiTiO2, Ti2O3 is also formed. The discharge voltage of the Zn/TiO2- aqueous LiOH cell and material utilization of the TiO2 as cathode are very low. Hence TiO2 is not suitable for use in any aqueous LiOH electrolyte battery. LiFePO4 (olivine-type structure) as a cathode undergoes electrooxidation in aqueous LiOH forming FePO4. However the subsequent reduction forms not only the original LiFePO4 but also Fe3O4. Thus the process is not completely reversible and hence LiFePO4 is not a suitable material for use as a cathode in aqueous battery systems. LiMnPO4 (olivine-type structure) undergoes reversible electrooxidation in aqueous LiOH forming MnPO4. The charge/discharge voltage profile of the Zn/MnPO4-aqueous LiOH cell, its coulombic efficiency and rechargeability are comparable to that of the cell using ã-MnO2. EMD and LiMnPO4 both have the potential for use in rechargeable batteries using aqueous LiOH as the electrolyte. Recommendations for further developmental work for such batteries are made.