Surface modification of Li-rich cathode materials for lithium-ion batteries with a PEDOT:PSS conducting polymer

Composites of lithium-rich Li_1.2Ni_0.2Mn_0.6O₂ and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are synthesized through coprecipitation followed by a wet coating method. In the resulting samples, the amorphous conductive polymer films on the surface of the Li_1.2Ni_0.2Mn_0.6O₂ particles are 5-20 nm thick. The electrochemical properties of Li_1.2Ni_0.2Mn_0.6O₂ are obviously enhanced after PEDOT:PSS coating. The composite sample with an optimal 3 wt % coating exhibits rate capability and cycling properties that are better than those of Li_1.2Ni_0.2Mn_0.6O₂, with an excellent initial discharge capacity of 286.5 mA h g^-1 at a current density of 0.1 C and a discharge capacity that remained at 146.9 mA h g^-1 at 1 C after 100 cycles. The improved performances are ascribed to the high conductivity of the PEDOT:PSS coating layer, which can improve the conductivity of the composite material. The PEDOT:PSS layer also suppresses the formation and growth of a solid electrolyte interface. Surface modification with PEDOT:PSS is a feasible approach for improving the comprehensive properties of cathode materials.