Chapter 2 describes the solid-state synthesis of LiNiVO4 and LiCoVO4. The materials are prepared at 800C and are phase pure, as shown by X-ray diffraction and have the inverse spinel structure. Due to the solid-state synthesis the particle size is quite large and the particle size distribution is large, between 0.1mm and 10 mm, even after ball-milling. The electrochemical results show that Li+ can electrochemically be extracted and inserted into these inverse spinel materials. Both LiNiVO4 and LiCoVO4 exhibit a low initial charge capacity, which drops significantly after the first cycle. The electrochemical behaviour of these materials is different as observed from the in-situ XRD measurements. The results clearly show that the lattice parameter of LiNiVO4 decreases from 8.215to 8.185during Li-extraction and increases to 8.205during Li-insertion. During the following cycles, the initial lattice parameter is not reached. The intensity of the diffraction peaks does not change during cycling, indicating a stable host structure, i.e., no cracking or internal stresses occur as a result of the Li-ion extraction or insertion processes. The in-situ measurements of LiCoVO4 reveal that two phases are formed during Li-extraction. This phase transformation takes place during the first cycle. This new phase has a lattice parameter of 8.261and its lattice parameter increases to 8.276 during Li-insertion. Furthermore, the in-situ results show that the lattice parameter of this new phase shifts during insertion and extraction of the Li-ions and that the lattice parameter of the initial phase does not shift. This is explained by a surface layer of shell formation, attributed to the low diffusion coefficient of the Li+ ions. This then accounts for the partial Li-ion extraction and, thus, limits the utilization of LiCoVO4, because a relatively large amount of Li-ions will remain in the bulk. The rather low electronic conductivity of these inverse spinels is the main reason for the low electrochemical performance. To enhance the electrochemical performance, the influence of dopants (Cr, Cu, Fe) on the structure and electrochemical properties on these inverse spinels was studied and presented in chapter 3. From the X-ray diffraction patterns, it was concluded that for doping concentrations of 10 mol% a single-phase material could be obtained via solid-state reaction. A dopant concentration exceeding 10 mol% resulted in a multi-phase system. The dopants are located at the tetrahedral and octahedral sites replacing either the Ni2+ or the Co2+ ions. The cyclic voltammograms of doped LiNiVO4 powders show the appearance of new reduction and oxidation peaks at different voltages. The peaks are attributed to different Ni2+ coordinations in the inverse spinel structure. The cyclic voltammograms of the doped LiCoVO4 materials, however, show one broad peak which is significantly higher than the redox peaks exhibited by undoped LiCoVO4. These materials exhibit an increased capacity, discharge voltage plateau, and better cyclability compared to undoped LiCoVO4. The dopants result in an increased stability and electrical conductivity. In the case of LiCoVO4 the dopants are located on octahedral sites thus forming a conductive pathway via the octahedral positions according to the site percolation theory. However, this theory cannot be applied to LiMxNi1-xVO4, since the dopants are located on the tetrahedral sites and, therefore, pushing the V5+ ions towards the octahedral sites. To reduce the particle size of the materials, the citric acid-assisted complex synthesis method was observed to be very effective to prepare sub-micron particles of doped LiCoVO4. TGA revealed that the crystallization was complete at 500C and from the high-temperature XRD (HT-XRD) diffraction patterns it was concluded that the initial crystallization of LiCoVO4 occurred between 250C and 300C. The X-ray diffraction patterns revealed a single phase material for the Cr- and Cu-doped LiCoVO4 and a second phase, i.e., Fe2O3 was found for the 8 and 10 mol% Fe-doped LiCoVO4. The lattice parameter of Cu-doped LiCoVO4 increased from 8.281 to 8.286 for 10 mol%. The lattice parameter for both the Fe- and Cr-doped LiCoVO4 decreased to 8.279 and 8.273 respectively. The assumption that the dopant replaces the Co2+ ions in the octahedral sites is confirmed by Raman spectroscopy results, which showed no new phases upon substitution. The spectrum was resolved and the band located at 475 cm-1 is attributed to the vibration of the Li-O-M bond. For the Fe3+ dopant this band shifts from 475 cm-1 to 485 cm-1 for the 6 mol% dopant concentration, while for the Cu2+ dopant the band shifts to 482 cm-1 for the 10 mol% concentration, and to 485 cm-1 for the 10 mol% Cr3+ dopant. A smaller shift is observed for the two broad bands located at 786 cm-1 and 810 cm-1, which are attributed to the stretching vibrations of the VO4 tetrahedron. The shift for the 6 mol% Fe3+ dopant is from 786 cm-1 to 789 cm-1, while for the 10mol% Cu2+ dopant the band shifts to 790 cm-1. For the Cr3+ dopant the band shifts to 788 cm-1. For the powders with a dopant concentration beyond 2 mol% the cyclic voltammograms exhibit two oxidation peaks in the first scan. The second oxidation peak is attributed to the oxidation of Co2+ to Co3+, which migrates from the octahedral site into the tetrahedral site. The use of a dopant, which enhances the electronic conductivity and the use of sub-micron based particles have substantially increased the electrochemical performance of the material. The enhanced charge capacity leads to an unstable system at low Li+ concentration, which results in the diffusion of V-ions within the structure. With in-situ Raman spectroscopy it was found that the cations dissolve in the electrolyte. The dissolution of 3d-metals during charging in a lithium-ion cell is a dominant fading mechanism of intercalation materials. A structural investigation to influence on the electronic and structural properties of the 6 mol%-doped LiCoVO4 was conducted and described in chapter 5. The results showed that for both Fe and Cr dopants the oxidation state was 3+ and that the oxidation state of Cu was 2+. The oxidation state of Co2+ did not change with the different dopants and it was assumed that V5+ partly changed to V4+ for charge compensation in case of the Fe and Cr dopants. The Fe- and Cr-doped inverse spinels showed and increase in the electrical conductivity from 10E-8 S/cm to 10E-7 S/cm at 50C. The Cu2+ substitution also led to an increase in the electrical conductivity but smaller. Rietveld refinement analyses of the inverse spinel led to the conclusion that no large structural reorientation occurred for the different doped LiCoVO4. This implies that the enhanced electronic conductivity is due to dopants located on the octahedral sites. In chapter 6 the influence of an Al2O3-coating on the electrochemical properties was conducted. LiCo0.94Fe0.06VO4 powders were coated with Al2O3 using a wet chemical method to prevent 3d metal dissolution. The morphology and structure of the coating have been characterized with SEM, HR-TEM, and XPS. It was found that the Al2O3 coating was amorphous and that the particles were not completely coated, approximately 30-40 % of the surface was covered. The Al2O3 coating had an average thickness of 10 nm. Cyclic Voltammetry measurements vs. Li/Li+ showed that the Al2O3-coated LiCo0.94Fe0.06VO4 sintered at 600C showed the best capacity retention and the cycle tests revealed that the materials still posses a discharge capacity of 76 mAh/g, even after 80 cycles. The improved cycling performance is attributed to the ability of the Al2O3 layer to neutralize the formed HF component in the liquid electrolyte.