Research On Preparation Of NiCo₂O₄ Supercapacitor Material By Spray Drying

Spinel NiCo2O4 is widely used in supercapacitors,electrocatalysts,optoelectronic devices and magnetic devices because of its excellent electrocatalytic activity,excellent corrosion resistance and chemical stability.At present,it is one of the materials with the highest experimental specific capacitance reported.However,NiCo2O4 supercapacitor has low energy density and poor conductivity,which limits its further application.In order to improve the energy density and conductivity of NiCo2O4 supercapacitor materials,this paper will focus on controlling nano-particles granularity and compositing metal oxides.In this paper,spherical porous NiCo2O4 materials with self-assembled nano-particles and micro-nano structured were successfully prepared by citric acid chelation method combined with spray drying technology.First,study the precursor solution and spray parameters,the optimal process parameters were obtained.The spherical NiCo2O4 precursors were prepared by n(Ni):n(CA)=1:3,ether to water ratio=1:2,chelation solution pH=8.0,spray solution pH=9.5,solvent volume=150 ml,spray temperature of 150/75℃,and peristaltic pump speed of 550 ml/h.Then,the porous spherical NiCo2O4 material having a micro-nano structure self-assembled by nano-particles is obtained after calcination at 300-450℃.Electrochemical tests show that the best electrochemical performance after calcination at 300℃.The NiCo2O4 electrode material calcined at 300 has a specific capacitance of 430.67 F g-1 at current density of 1 A g-1,and the capacity retention rate is 100%after 3000 cycles.The test results of an asymmetric supercapacitor device show that the specific capacitance is 37.06 F g-1 at 1 A g-1 current density,and the energy density is 13.18 Wh kg-1.The spherical material of the nanoporous channel facilitates the release of lattice distortion stress during the charge and discharge process,maintains the structural stability of the crystal,and improves the cycle life.In order to further improve the electrochemical performance of NiCo2O4,the micro-nano structure NiCo2O4 was composited with NiO to obtain NiCo2O4/Nio material.The samples were tested and characterized by different amounts of NiO.The results show that the NiCo2O4/NiO composites still retain nano-particles and porous structures.When the Ni(NO3)2 concentration is 10%,the NiCo2O4/NiO particles have the largest specific surface area(47.773 m2 g-1)and the highest specific capacity.The specific capacitance of NiCo2O4/NiO particles is 640.6 and 566 F g-1 at 1 and 10 A g-1 current densities,respectively,and they have excellent multiplier characteristics(88.35%).The test results of an asymmetric supercapacitor device show that the specific capacitance is 50.44 F g’1 at current density of 1 A g-1 and the energy density increased to 17.93 Wh kg-1.After 14,000 cycles at current density of 4 A g-1,the specific capacity is 42.5 F g-1 and the capacitance retention rate is 100%.It has excellent stability.The surface of NiCo2O4/NiO is rough and maintains the characteristics of porous,micro-nano structure,spherical shape,specific surface area,and the area of the sample contacting the electrolyte is further increased.More contact sites further improve the electrochemical performance of the material.