Improvement of cycling stability of Li 1. 2 Mn 0 . 54 Co 0 . 13 Ni 0 . 13 O 2 microrods cathode material modified with in situ polymerization of aniline in HTFSI solution

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A thin polyaniline layer that was covered on the surface of the microrod-like lithium-rich Mn-based oxide (LMO, Li1.2Mn0.54Co0.13Ni0.13O2) was formed by in-situ polymerization of the aniline monomer in HCl or (CF3SO2)2NH (HTFSI) aqueous solution. The results of morphology analysis and structural characterization show that the uniform polyaniline coating layer has a thickness of 6 to 8 nm and the polymerization process does not spoil the integrity of the LMO microstructure. Electrochemical impedance spectroscopy and constant charge/discharge measurement show that polyaniline coating can significantly decrease the interfacial charge transfer resistance, and improve cyclic stability by reducing electrolyte corrosion. Cycling at the current density of 0.1 A g−1 for 100 cycles, the polyaniline-coated LMO synthesized in HTFSI acidic media exhibits the discharge capacity of 212.2 mAh g−1and high stability (91.98% retention of initial capacity). The high performance is a result of the activation of LMO in HTFSI acidic solution and the role of the (CF3SO2)2N− counterions in the polyaniline chains.