The high-frequency induction heating method is an attractive way to synthesize LiFePO4/C within a few minutes. We optimize the heating conditions by a carbon crucible for the homogeneous heating of a precursor pellet from both sides. Compared with our previous samples, the lattice parameters of the LiFePO4/C synthesized in this work (an optimized sample) are improved and are much closer to the values reported by Padhi et al. Although the primary particle size of the optimized sample is slightly larger than that of the previous samples, it is sufficiently small to fully utilize the electrochemical performances of LiFePO4. We reduced the internal charge-transfer resistance of the optimized sample by improving the crystal structure because the Nyquist plots of the electrodes indicate decreased resistance, even though the optimized sample's electronic conductivity is almost the same as that of the previous sample. The electrode based on the optimized sample shows a specific discharge capacity of 168.0 mAh g−1, which achieves 99% theoretical specific capacity of the LiFePO4 phase. Moreover, its charge–discharge rate performance is superior to that of the previous sample.