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.