Nanoscale LiFePO₄ and Li₄Ti₅O₁₂ for high rate Li-ion batteries

The electrochemical performances of nanoscale LiFePO₄ and Li₄Ti₅O₁₂ materials are described in this paper. The nanomaterials were synthesized by pyrolysis of an aerosol precursor. Both compositions required moderate heat-treatment to become electrochemically active. LiFePO₄ nanoparticles were coated with a uniform, 2–4 nm thick carbon coating using an organic precursor in the heat-treatment step and showed a high tap density of 1.24g/cm³ despite the 50–100 nm particle size and 2.9 wt % carbon content. Li₄Ti₅O₁₂ nanoparticles were between 50 and 200 nm and showed a tap density of 0.8g/cm³. The nanomaterials were tested both in half-cell configurations against Li metal and in LiFePO₄/Li₄Ti₅O₁₂ full cells. Nano-LiFePO₄ showed a high discharge rate capability with values of 150 and 138 mAh/g at C/25 and 5C, respectively, after constant C/25 charges. Nano-Li₄Ti₅O₁₂ also showed a high charge capability with values of 148 and 138 mAh/g at C/25 and 5C, respectively, after constant C/25 discharges; the discharge (lithiation) capability was comparatively slower. LiFePO₄/Li₄Ti₅O₁₂ full cells deliver charge/discharge capacity values of 150 and 122 mAh/g at C/5 and 5C, respectively.