Glucose Modified Nickel-Cobalt Nanosheets And Electrochemistry Properties Of Alkaline Zinc-Based Batteries

The deteriorating environmental problems caused by the development and use of primary energy sources,there is a growing interest in developing green and efficient energy storage devices.Currently,lithium-ion batteries are a safety concern due to their use of organic electrolytes,which can easily cause explosions.Aqueous rechargeable alkaline nickel-based batteries have good prospects for development due to their high theoretical capacity,low cost and high safety.However,alkaline Ni-Zn batteries suffer from self-corrosion of the positive electrode,resulting in reduced contact with the electrolyte.Metal hydroxides have a high specific capacity and Ni（OH）₂ and Co（OH）₂ have outstanding redox properties and are relatively abundant.However,the nickel-cobalt hydroxide preparation process has problems such as particle agglomeration,reduced specific surface area,reduced number of active centers,and short electrode life.Hydroxide intercalation by glucose facilitates the diffusion of OH-while accelerating redox kinetics.This thesis constructs a glucose-optimized Ni Co LDH and Ni Co Se electrode material and energy storage mechanisms were systematically investigated.The main studies are as follows:1.Preparation of glucose-modified nickel-cobalt hydroxides by a one-step hydrothermal method.Research shows that glucose can increase the layer spacing between hydroxide nanosheets and speed up electron transport.And the glucose content was 2 mmol(a specific capacity of 236 m Ah g^-1 could be achieved at 1 A g^-1),and it was able to maintain 60% of the highest capacity for 2000 cycles at 10 A g^-1.In addition,the prepared nickel-cobalt hydroxide is used as the positive electrode material and commercial zinc flakes are used as the negative electrode material,alkaline Ni Co LDH-G2//Zn battery can achieve a specific capacity of 355 m Ah g^-1 at 3 A g^-1 and retain 79% of their starting capacity after 500 cycles of charging and discharging.2.A one-step hydrothermal method was used to improve the temperature of the reaction and again to regulate the different concentrations of glucose to investigate the nickel-cobalt hydroxide.Improved temperature promotes the formation and growth of crystals with a more complete and ordered structure.In addition glucose can fill gaps between layers,reducing structural deformation and destruction of active sites,and can also enhance electron transfer in Ni Co LDH.It was found that the specific capacity and cycling stability of nickel-cobalt hydroxide were the highest when the glucose content was 1.5 mmol.A specific capacity of 224 m Ah g^-1 can be achieved at 1 A g^-1,and it can maintain 86% of the highest capacity by cycling 2000 revolutions at 10 A g^-1,in addition,the specific capacity at 40 A g^-1 is 76% of that at 1 A g^-1,reflecting the excellent multiplicative performance.Finally,Ni Co LDH-G1.5was used as the cathode material to assemble Ni Co LDH-G1.5//Zn alkaline Ni-Zn battery.Ni Co LDH-G1.5//Zn devices can reach a specific capacity of 180 m Ah g^-1 at 20 A g^-1,and the capacity retention rate is 72% of the maximum capacity after 2000 cycles.3.Nickel-cobalt hydroxide precursors were prepared by hydrothermal method,followed by high temperature selenization to obtain glucose-optimized Ni Co Se nanosheets.Glucose acts as a reducing agent to facilitate the selenisation reaction.The simultaneous embedding of glucose into Ni Co Se nanosheets promotes lattice modulation and grain size reduction of the material,thereby increasing the specific surface area.When the amount of glucose was 2mmol,the obtained electrode materials could reach a specific capacity of 164 m Ah g^-1 at 1 A g^-1,and were able to maintain 82% of the maximum capacity by cycling for 1000 cycles at 10 A g^-1,showing good cycling stability.In addition,the prepared Ni Co Se nanosheets as the positive electrode material and zinc sheets as the negative electrode were encapsulated into alkaline Ni-Zn battery,which could reach a maximum specific capacity of 205 m Ah g^-1 at 3 A g^-1 and a capacity retention rate of 137.8% after 500 cycles.In summary,glucose-intercalated nickel-cobalt compound nanosheets,which exhibit excellent electrochemical properties during charging and discharging,can in turn well improve the capacity of nickel-cobalt compounds and their stability,providing a new solution idea for the development of alkaline nickel-zinc batteries.