Conductive Polypyrrole Coated Hollow NiCo2O4 Microspheres as Anode Material with Improved Pseudocapacitive Contribution and Enhanced Conductivity for Lithium‐Ion Batteries

Abstract Conductive polypyrrole (PPy) coated urchin‐like hollow NiCo 2 O 4 (NCO) porous microspheres (NCO@PPy) were synthesized by an easy and cost‐effective method. The NCO@PPy shows improved cycling stability and rate capability in comparison with the pure NiCo 2 O 4 when used as anode material for lithium‐ion batteries. In order to undersatnd the improvement of electrochemical performance of NCO@PPy, kinetic parameters and the lithium storage mechanism are investigated by EIS spectra and sweep voltammetry measurements. The sweep‐rate‐dependent CV (cyclic voltammetry) curves demonstrate an ever‐increasing redox capacitive‐controlled lithium storage originating from both, the hierarchical hollow structure and the effect of the PPy coating layer. The apparent Li + ion diffusion coefficient of NCO@PPy and NCO derived from EIS and CV curves indicates that PPy coating layer reduces the charge‐transfer resistances and improves the lithium‐ion diffusion coefficient.