Design And Research Of Kilowatt-Scale Zinc-Nickel Single-Flow Batteries For Large-Scale Energy Storage Applications

Achieving the large-scale application of energy storage batteries and power stacks is a necessary cornerstone for the effective use of renewable energy,and an effective guarantee for achieving China’s dual carbon targets.Due to the intermittent and uncontrollable nature of renewable energy sources such as wind and solar power,comprehensive energy storage facilities are required to bring their renewable energy potential into exert,making energy saving and emission reduction a reality and enabling the dual carbon target to be met more quickly.As a star product in the field of large-scale energy storage,flow batteries are developing at a rapid pace in recent years,and it is important to develop a higher safety,cheaper,longer life,and the more energy-efficient stack of kilowatt-scale flow batteries for practical energy use.Based on this,this thesis is application-oriented and takes zinc-nickel flow batteries as the object.By understanding the basic laws between different operating conditions and the performance of conventional zinc-nickel flow batteries under the basic model and investigating their operating limit boundaries,a new cell structure for cavity-free zinc-nickel flow batteries is designed and a step-by-step scale-up of the cavity-free zinc-nickel flow batteries under the new structure is achieved,and finally a kilowatt-scale zinc-nickel flow batteries is realized.The design and assembly of the kilowatt-scale zinc-nickel flow batteries were achieved.The main research results and innovations are as follows:1.The relationship between the"operating parameters-performance"of zinc-nickel single-flow batteries have been identified.As the tip of the iceberg of the liquid current battery industry,there are very few research teams or literature references compared to the relatively mature all-vanadium and zinc-bromine liquid current battery systems,so there is a need for a systematic and complete understanding of the basic laws and operating limit boundary parameter conditions between different operating conditions and performance of zinc-nickel single-flow batteries,to obtain the parameter conditions and operating limit boundary parameter conditions for zinc-nickel single-flow batteries.To obtain the optimum operating conditions and operating limit boundary parameters for zinc-nickel single-flow batteries,and to provide valuable references for the subsequent operating conditions and parameters of zinc-nickel single-flow batteries for large-scale energy storage practical applications.In this work,a conventional zinc nickel single flow battery with an active reaction area of 1 cm×1 cm is defined as the basic model of zinc-nickel single-flow batteries,and the zinc-nickel single-flow batteries under the basic model is tested to find the relationship between the"operating parameters-performance"of the zinc-nickel single-flow batteries and to select the optimal operating conditions.Operating at an operating current density of 35 mA cm^-2 gives an excellent energy efficiency of 78.35%and enables stable operation for almost 100 revolutions.However,it was also found that the reason for the short lifetime of the zinc-nickel mono-single flow batteries is mainly due to the disadvantages of its structural design under the conventional battery structure.2.A new structure for cavity-free zinc-nickel liquid flow batteries has been designed.Conventional zinc nickel mono-single flow batteries have a cavity structure between the positive and negative electrodes inside the cell,which is mainly used for electrolyte flow and as a"diaphragm"to separate the positive and negative electrodes.However,this cavity structure is favored for zinc deposition,and over time,zinc accumulation and zinc dendrites caused by zinc deposition lead to short circuits inside the positive and negative electrodes.For this reason,we have designed a new cell structure for a cavity-free zinc nickel single-flow battery.In this new structure,the zinc negative electrode uses an inert conductive porous electrode and there is no cavity inside the cell,zinc deposition is forced to occur in the inert conductive porous electrode.On the other hand,due to the porosity of the porous electrodes and the absence of cavities inside the cell,the zinc deposition and dissolution reactions are forced to take place only inside the inert,conductive porous electrodes,thus limiting the deposition of zinc crystals.In this work,a new structure of cavity-free zinc-nickel single-flow batteries is designed to solve the problem of short-circuiting of positive and negative electrodes due to zinc dendrite growth,which leads to short battery life.At an operating current density of 35 mA cm^-2,the energy efficiency can reach a maximum of 84.35%,and the battery can operate stably for nearly 650 cycles with an energy efficiency of over 75%,which is a sixfold increase in cycle life compared to conventional structures.3.The development and assembly of a stack of kilowatt-scale cavity-free zinc-nickel single-flow batteries for large-scale energy storage applications.As the core idea of this project is to design and develop energy storage devices for scale-up energy storage applications,this work is application-oriented and launched towards practical applications of scale-up energy storage,using the idea of step-by-step scaling up of chemical reactors,starting from small cells of one square centimeter in the laboratory and scaling up cavity-free zinc-nickel single-flow batteries step-by-step to the thousand square centimeter level.However,there are heterogeneities and inconsistencies in mass transfer,heat transfer,and reaction during the step-by-step scale-up process,so there is a need to gain insight into the reasons for the existence of the scale-up effect and to find the rate-determining factor among the many factors of the scale-up effect.The present work aims to overcome the amplification effect by successfully designing,developing,and assembling a single stack of kilowatt-scale cavity-free zinc-nickel single-flow batteries for large-scale energy storage applications,with an operating current of 44.415 A(current density of 35 mA cm^-2),a rated discharge voltage of 65.80 V and a discharge power of 2.034 k W.The design and assembly of a liquid current battery from the laboratory level of one square centimeter to the pilot level of a thousand square centimeters is a step-by-step approach.