A new cathode material based on C-LiFe_0.4Mn_0.6PO₄ and conducting composite binder poly(3,4-ethylenedioxythiopene):poly(styrene sulfonate)/carboxymethylcellulose (PEDOT:PSS/CMC) was prepared. The obtained composite cathode material containing 96 wt% of C-LiFe_0.4Mn_0.6PO₄ showed the discharge capacity 140 mA h g^-1 at 0.2 C and excellent rate capability with discharge capacities of 130 mA h g^-1 at 5 C and 118 mA h g^-1 at 10 C as well as good cycling stability. The cathode material composition with water-based PEDOT:PSS/CMC binder showed remarkable improvement in high-rate performance with increase of capacity up to 45% at 10 C current density in comparison to that of conventional PVDF-bound electrode.