Study On The Preparation And Performance Of Nickel-Based Materials For Nickel-Zinc Batteries

With the popularity of mobile and wearable electronic devices,hybrid and electric vehicles in daily life,their demand for high-performance,high-security,and high-efficiency batteries continues to grow.Nickel-zinc?Ni-Zn?batteries are one of the promising energy storage devices due to their high efficiency,high output voltage?1.73V?and good safety.However,nickel cathodes have insufficient active sites and low ion diffusion speed,which leads to low cycle life and low energy density,which hinders the commercial development of Ni-Zn batteries.In order to solve these problems,this paper improves and enhances the performance of nickel cathode active material Ni?OH?₂ by ion doping and designing new nanostructures.The molybdenum-doped Ni?OH?₂ was synthesized by a simple method,and its physical and chemical properties were investigated in detail.Transmission electron microscopy?TEM?shows that it is a dense,high-order amorphous structure composed of grains,and this structure can enrich reactive sites and can create efficient ion diffusion channels;The influence of the addition ratio of nickel and molybdenum on the electrochemical performance of Ni?OH?₂ was explored;Also explored the proton diffusion coefficient of Mo-Ni?OH?2;In addition,the potential of Mo-Ni?OH?₂ as a nickel cathode in nickel-zinc batteries was also studied.The research results show that the average discharge specific capacity of the Mo-Ni?OH?2 electrode is 173 mAh g^-1,and in the state of deep discharge,the discharge specific capacity can reach up to 300 mAh g^-1.What's more,the Mo-Ni?OH?₂ electrode is able to cycle stably for 1200 times,with a capacity decay rate of only 2.6%,showing good cycle performance.In addition,3D nano-flower-like Ni?OH?₂ was formed by self-assembly of phosphomolybdic acid?HPMo?for the first time,and its composition structure and elemental composition were analyzed by X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?.The morphology of the nickel cathode before and after cycling was observed and compared by scanning electron microscope?SEM?.Transmission electron microscopy?TEM?was used to explore its internal structure.The electrochemical reversibility was investigated using methods such as cyclic voltammetry?CV?.When it is evaluated as a cathode material for nickel-zinc batteries,at a current density of 2.5 A g^-1,the discharge capacity of the 3D flower-shaped Ni?OH?₂ electrode can reach 277.5 mAh g^-1?cut-off voltage 1.5 V?,and when the cathode discharges at deep,the maximum hourly specific capacity can reach 346.9 mAh g^-1;besides,at a current density of 5 A g^-1,it can circulate 10,000 times stably.Its excellent electrochemical performance is attributed to the fact that the three-dimensional flower-like structure provides enough electrochemical reaction sites.The porous channels between the petals increase the contact area between the active material and the electrolyte,reducing electrode expansion and polarization,and improving the efficiency of nickel-zinc batteries.What's more,this paper proposes a possible growth mechanism for 3D flower-like Ni?OH?₂electrode materials,which provides a new direction for the preparation of three-dimensional nanostructured materials.