| As a promising zinc-based battery,zinc–nickel battery（ZNB）has many advantages,such as high power density,high nominal voltage,intrinsic safety,high environmental friendliness,etc.ZNB has potential to become an alternative of lead-acid battery.However,the development of ZNB is still largely confined to the laboratory research stage,and few studies have comprehensively demonstrated the application potential of ZNB as an energy storage technology from the technical,application and economic points of view.In addition,compared with commercial batteries,ZNB has poor cycle life and shelf life.The reasons related to the poor technical performances have not been systematically studied,and thus the modification direction of ZNB is unclear.At present,the studies on ZNB in the academia are all focused on the modification of single battery components to address limited problems（e.g.,dendrite and deformation）.There is a lack of modification strategies that give consideration to both scientific nature and mass production ability to comprehensively improve the performance of ZNB.Based on the above facts,intrinsically safe ZNB with capacities of 20 Ah and 75Ah were firstly developed in this work.The performance and application potential of ZNB were studied by comparing ZNB with commercial Lead-acid batteries（LAB）.Compared with LAB,ZNB has better rate performance,higher mass and volume energy density.In addition,the application potential of ZNB battery stacks as power sources of electric bicycle and hybrid electric vehicle is demonstrated.Solar power system and 10 k Wh ZNB energy storage system were also developed.The corresponding working condition curves were recorded to prove the application potential of ZNB in energy storage system.Finally,the economic analysis of ZNB and LAB was carried out.When operating a energy storage system under high discharge rate,ZNB has lower cost.This work demonstrates the commercial potential of ZNB.The advantages and disadvantages of ZNB compared with LAB are demonstrated comprehensively.Although ZNB has a great application prospect in the energy storage market,there is still a gap between studies and commercial application.In this work,the failure reasons leading to the poor cycling life and shelf life of ZNB are proposed to accurately guide the future studies.A ZNB containing a negative plate and a positive plate based on components 20 Ah battery was developed for basic research.The failure mechanism of ZNB was verified by applying various in-situ computed tomography accompanied with theoretical calculation.It is found that zinc deposition is uneven during the cycling,which eventually leads to dendrite growth to induce internal short circuit.In addition,serious hydrogen evolution reaction would happen during storage process,and the electrolyte would be evaporated.During the floating charging process,the degradation of ZNB performance is mainly affected by the large amount of oxygen generated by the oxygen evolution reaction from the cathode.This study systematically demonstrates the different failure problems existing in different working conditions of ZNB,and provides a clear idea for the further modification of ZNB.In order to comprehensively address the failure problems of ZNB to improve the cycling life and shelf life,a simple strategy was proposed and a functional composite separator（FC）separator was developed.The performance of ZNB can be improved by stably modifying the characteristics of anode-electrolyte interface.During the cycling process,the FC separator interacts with the anode interface and guides the even zinc deposition.As a result,the battery assembled with FC separator achieves superb cycling life of 1435 h（848th cycle）with discharge voltage higher than 1.2 V.In addition,the hydrogen evolution reaction of the battery can be slowed down under the function of organic phase from the FC separator.The water retention ability has also been improved to ensure good storage performance,in which the open circuit voltage of the battery is higher than 1.63 V after 618 h under a high temperature of60°C.Besides,the negative effect brought by oxygen from cathodes has been reduced.Consequently,the battery keeps a high discharge capacity without breakdown for more than 800 h floating charge at 60°C.The study provides a new way for preparation of functional separators.On the basis of the above studies,there is still room for further improvement of the performance of ZNB.For example,in order to improve the cycling life,the current density distributed on the anode surface is also an important factor that needs to be considered for suppression of dendrite growth.Herein,a porous-structured“mutifunctional layered conductive”（MLC）separator with four functions was developed to comprehensively address problems of ZNB.MLC separator was prepared by a simple and effective strategy,in which various polymer and nano-sized inorganic compositions can be easily integrated to functionalize the separator.MLC separator can effectively suppress dendrites and deformation of the anode,while avoiding the anode collapse under the extended conductive network for an excellent cycling life of ZNB.Furthermore,the side reactions and electrolyte loss have been mitigated to improve the shelf life of ZNB.Consequently,MLC separator enables an impressive cycling life of ZNB for 1672 h（1094 cycles）with a voltage platform higher than 1.3 V at a high current density of 55.3 m A cm–2,which has a significant improvement than ZNB assembled with FC separator.Besides,ZNB can be stored and floating charged for a long time,respectively,under a high temperature of 60℃.Finally,the MLC separator has been successfully applied in the small energy storage device to prove its application potential. |
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