Electrode Material Design And Electrolyte Modification For Aqueous Zinc Ion Batteries

Aqueous zinc ion batteries with the merits of low cost,intrinsic safety and environmental friendliness are attractive in the field of grid-scale energy storage.However,the strong electrostatic interaction between cathode materials based on(de)insertion mechanism and high charge density zinc ion leads to poor zinc ion diffusion kinetics and cathode structure collapse.Iodine cathode based on conversion mechanism can deliver a rapid and reversible reaction.However,"shuttle effect" blocks the practical application of iodine battery.As for anode,dendrites are unavoidable due to the concentration gradient of zinc ions and tip effect.In addition,hydrogen evolution,corrosion and passivation occur continuously due to the absence of solid electrolyte interphase.In view of the above challenges,electrode material design and electrolyte additives are employed to promote the electrochemical performance of aqueous zinc ion batteries.The main research contents and results are as follows:(1)Conductive polyaniline is employed as host to inhibit "shuttle effect" through the strong electrostatic interaction between polyaniline and polyiodide.During redox process,polyiodide is doped in polyaniline backbone in the form of I5-,I3-or I-,thus avoiding polyiodide dissolution.In addition,polyiodide doping maintains the conductivity of polyaniline and promotes the redox kinetics.As a result,high reversible capacity of 160 mAh g-1 and capacity retention of 79%after 700 cycles at a current density of 1.5 A g-1 are obtained.(2)Nicotinamide is employed as an electrolyte additive to regulate zinc deposition.Nicotinamide adsorbed on the surface of zinc anode can hinder zinc ion 2D diffusion,increase the nucleation overpotential and make nucleation finer,thus guiding uniform zinc deposition.Meanwhile,the adsorption of nicotinamide is prior to H2O,which can inhibit the side reactions induced by water.With the assistance of 0.1 wt%nicotinamide additive,the lifespan of the symmetric cell is extended to 200 h at 5 mA cm-2 for 5 mAh cm-2.(3)In-situ constructing polyacrylamide interphase enables uniform zinc deposition.Catalyzed by zinc ions,acrylamide molecules adsorbed on the surface of zinc foil polymerize into polyacrylamide.Compared with traditional spin coating,the in-situ polymer layer is more uniform and can provide better affinity with zinc electrode.The carbonyl groups in polyacrylamide can coordinate with Zn2+to restrict 2D diffusion,increase the nucleation overpotential and regulate homogeneous zinc deposition.As a result,5 wt%acrylamide additive prolongs battery life to 380 h at 2 mA cm-2 for 4 mAh cm-2.(4)An artificial solid electrolyte interphase is constructed by controllably electrodepositing to regulate zinc deposition.The porous and insulated ZIF-8 is an ideal material for artificial solid electrolyte interphase.Constructing a compact and continuous ZIF-8 layer can not only induce bottom deposition and alleviate dendrite formation,but also act as a physical barrier to avoid side reactions.Consequently,a prolonged battery life of over 5000 cycles at 10 mA cm-2 for 1 mAh cm-2 is achieved.(5)9,10-anthraquinone is used as anode material instead of metal zinc to construct a "rocking chair" zinc ion battery.The potential of 9,10-anthraquinone(～0.45 V vs.Zn2+/Zn)is higher than zinc plating/striping,which can eliminate dendrite formation and side reactions.The excellent cycling stability with capacity retention of 94.4%and high specific capacity of 189.5 mAh g-1 after 500 cycles in "full-battery configuration"are achieved.