Battery active materials are evaluated using numerous material characterization techniques for fundamental understanding, comparative analysis during research and development, and for quality control during manufacturing. Electrochemical properties of the active materials also need to be investigated and validated, and this analysis is very time and material intensive generally requiring electrode fabrication, cell assembly and cell cycling. In addition, evaluating active materials electrochemically in battery cells can be complicated by the electrode microstructure and the contributions of other components within the cell that are not the active materials. In this report, an active material characterization method is demonstrated to provide electrochemical insights for lithium-ion cathode materials by dispersing them into aqueous electrolyte and flowing through an electrochemical reaction cell. This method requires very little active material and time to conduct the measurements, typically requiring under 0.1 grams of material and less than 10minutes. The measured resistance from this technique provides insights into the electrochemical performance of the active material and generally correlates to the rate capability. This measured resistance is insensitive to other electrode components or electrode microstructure because there is no electrode fabrication step. LiFePO4 was chosen as a commercial material for initial demonstration of the technique.