Co-substituted Ni(OH)2/carbon nanofiber (CNF) composite was synthesized by chemical coprecipitation method. X-ray powder diffraction (XRD) patterns evidenced that it was an intermediate phase with α-β structure. Transmission electron microscopy (TEM) images suggested crystalline α-β-NixCo1-x(OH)2 nanosheets growth on the surface of CNFs. The testing results of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge-discharge showed that the composites had high specific capacitances, low electrochemical reaction impedance, and long cycle stability. Using the composite as a cathodic active material, a specific capacity of assembled NiZn pouch cells ranged from 160.25 mAh·g−1 at current density of 15 mA cm−2 to 91.35 mAh·g−1 at current density of 50 mA cm−2. In addition, those NiZn pouch cells have excellent rate performance and long cycle stability. After 1500 cycles, the energy capacity retained 215.24 Wh·kg−1, 98% of the initial value. The relationship between structure and the electrochemical performance was analyzed and discussed in detail. Intermediate phase α-β-Ni1-xCox(OH)2/CNF composites can be a promising cathodic active material for Ni-based batteries.