Electrode design is an essential task for successful development of lithium-ion batteries. Provided that the same materials are given, proper dimensioning of the electrodes and balanced composition of the materials in them can maximize the cell performance, such as the discharge capacity. However, many electrode design parameters have conflicting effects on the performance, and thus careful optimization of these parameters is required. This study experimentally investigated the effects of several electrode design parameters on the performance of lithium ion cells with a LiFePO4 cathode and a natural graphite anode, focusing on their high current operations. The conflicting effects of the conductor ratio (the weight fraction of electronic particle additives), electrode thickness, and electrode density (porosity) on the cell capacity were studied. In addition, a detailed one-dimensional electrochemical model was also used to simulate the observed performance characteristics and to identify their underlying mechanisms limiting the performance. Based on the experimental and numerical results, the optimal ranges for the electrode design parameters were discussed to achieve better performance of the LiFePO4/graphite batteries.