Enhanced Cycling and Structure Stability of an Electron Transfer-Accelerating Polymer Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)-Covered Mn-Based Layered Cathode with Ga3+ Doping for a Li-Ion Battery.

ABSTRACT

Mn-based cathode material Li1.20Mn0.52Ni0.20Co0.08O2 was proposed and ameliorated by surface-coating poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOTPSS) and doping Ga3+. X-ray diffraction and high-resolution transmission electron microscopy studies revealed that part of Ga3+ replacing the Ni site could reduce the Li+/Ni2+ mixing by forming a well-ordered layered structure and a homogeneous coating layer of PEDOTPSS is covered on the surface of Li1.20Mn0.52Ni0.19Co0.08Ga0.01O2. The results of the electrochemical studies demonstrated the higher initial charging-discharging Coulombic efficiency, and outstanding rate capabilities and cyclic performance were obtained for the PEDOTPSS-covered and Ga3+-doped samples. Especially, 2 wt % PEDOTPSS-coated Li1.20Mn0.52Ni0.19Co0.08Ga0.01O2 delivered 38.3 mAh g-1, which is larger than the pristine cathode at a 5C high rate. Meanwhile, it could retain 189.6 mAh g-1 (90.3% of its initial discharge capacity at 45 °C) after 300 cycles with a 1C rate, while the pristine cathode only delivered 149.7 mAh g-1 with 80.7% cycling retention left. The results strongly suggested that such PEDOTPSS-coated and Ga3+-doped Mn-based layered structure materials demonstrated high potential as a cathode candidate especially for high-energy applications.