Facile synthesis of polypyrrole-modified Li5Cr7Ti6O25 with improved rate performance as negative electrode material for Li-ion batteries

Pristine Li5Cr7Ti6O25 and polypyrrole-modified Li5Cr7Ti6O25 materials are successfully synthesized by a facile sol-gel process. Based on the X-ray diffraction pattern and high-resolution transmission electron microscopy, a homogeneous polypyrrole layer is successfully coated on the surface of Li5Cr7Ti6O25 particles. The polypyrrole modification improves the reversibility and migration ability of lithium intercalation/deintercalation and reduces the charge-transfer reaction resistance. Li5Cr7Ti6O25@ polypyrrole shows higher delithiation/lithiation capacities and more excellent cycling performance at different charge-discharge rates than the pristine one. Li5Cr7Ti6O25@PolYPyrrole delivers a delithiation capacity of 115.9 mAh.g(-1) with 87.23% capacity retention cycled at 10C/3 rate after 300 cycles and a delithiation capacity of 132 mAh g(-1) with 72.2% capacity retention cycled at 20C/3 charge-discharge rate after 150 cycles. Hence, polypyrrole coating can be considered as an effective way to enhance the electrochemical property of Li5Cr7Ti6O25 for advanced Li-ion battery, and the effective design strategy may be used to improve the lithium storage capacity and cycling stability of other Ti-based negative electrodes.