Based on chemical, structural and physical - electrochemical analysis, some of the most important parameters of Ni-based cathode materials for metal hydride and Li-ion/polymer techniques are identified and correlated to the electrochemical performance. In case of nickel hydroxide active materials, a diffusion model is presented to understand the experimental well-founded correlation between capacity and crystallite size/lattice defect density. By modelling the charge/discharge curves, some of the essential parameters such as the diffusion coefficients of the NiOOH-Ni(OH)(2) material can be calculated and correlated to the FWHM-value and other structural features. For advanced Li(Ni,Co, Me) -oxides, as the most likely future alternative to the presently dominating LiCoO2 cathode material, safety is a major issue. Based on a new material synthesis and processing, safety aspects are discussed especially in relation to doping and microstructural features of the Li(Ni,Co,Me)-oxides. By combining different measures, the onset temperature of critical exothermic reactions of the charged Li(Ni,Co,Me)-oxides can be considerably shifted to higher values without a strong decrease in electrochemical capacity.