Influence of carbon coating and PANI modification on the electrochemical performance of Li4Ti5O12

The Li4Ti5O12/polyaniline and Li4Ti5O12/С/polyaniline composite materials with different lithium titanate/aniline ratio of 8:1, 4:1, 2:1, 1:1, 1:2, and 1:4 were synthesized by in situ polyaniline (PANI) polymerization. The materials were characterized by high-resolution TEM, X-ray powder diffraction, IR spectroscopy, and TGA. It was shown that polyaniline is uniformly distributed over the surface of Li4Ti5O12 or Li4Ti5O12/С composite. For the sample with the minimum polyaniline content (Li4Ti5O12/С/PANI (8:1)), the PANI layer thickness is 2–3 nm and contains polyaniline in the most conductive (emeraldine) form. The lithium titanate modification with polyaniline results in sharp increase in the electronic conductivity of materials from ~ 10−11 Ohm-1 cm−1 for Li4Ti5O12 to 10−4 Ohm-1 cm−1 for Li4Ti5O12/C/PANI. With increasing polyaniline content, the electrochemical capacity decreases for all samples, including carbon-coated and uncoated ones. The highest discharge capacity at current density < 800 mA g−1 is attained for the Li4Ti5O12/С/PANI (8:1) composite.