Memristors based on mixed anionic-electronic conducting oxides are promising devices for future data storage and information technology with applications such as non-volatile memory or neuromorphic computing. Unlike transistors solely operating on electronic carriers, these memristors rely, in their switch characteristics, on defect kinetics of both oxygen vacancies and electronic carriers through a valence change mechanism. Here, Pt vertical bar SrTiO3-delta vertical bar |Pt structures are fabricated as a model material in terms of its mixed defects which show stable resistive switching. To date, experimental proof for memristance is characterized in hysteretic current-voltage profiles; however, the mixed anionic-electronic defect kinetics that can describe the material characteristics in the dynamic resistive switching are still missing. It is shown that chronoamperometry and bias-dependent resistive measurements are powerful methods to gain complimentary insights into material-dependent diffusion characteristics of memristors. For example, capacitive, memristive and limiting currents towards the equilibrium state can successfully be separated. The memristor-based Cottrell analysis is proposed to study diffusion kinetics for mixed conducting memristor materials. It is found that oxygen diffusion coefficients increase up to 3 x 10(-15) m(2)s(-1) for applied bias up to 3.8 V for SrTiO3-delta memristors. These newly accessible diffusion characteristics allow for improving materials and implicate field strength requirements to optimize operation towards enhanced performance metrics for valence change memristors.