Aqueous Rechargeable Nickel-Zinc Batteries:From Nickel-Based Materials Design To Performance

With the popularity of portable electronic products,energy storage devices with high specific capacity,safety,and long cycling life are still a research hotspot.Aqueous nickel-zinc batteries have received increasing attention due to their low production costs,use of nonflammable aqueous electrolytes,and abundant raw materials.Meanwhile,other properties of electrode materials,such as electrochemical activity,specific surface area,capacity,energy/power density,and cycling stability,play an important role in battery performance.To date,many nickel-based materials,such as nickel hydroxide,nickel oxide,nickel sulfide and their composites with carbon materials,have been extensively studied as cathode materials for nickel-zinc batteries(NZBs).Among these compounds,nickel hydroxide has been extensively studied as a promising cathode material for batteries.Among them,?-Ni(OH)2 has high bulk density and stability,and can be directly converted into ?-NiOOH without obvious volume expansion when charged in alkaline solution,which is beneficial to maintain good cycling performance.Metal-organic framework(MOF)materials,a class of porous crystalline materials composed of metal ions/clusters and organic linkers,with tunable pore sizes and open metal sites,are promising candidates as electrode materials.Among them,bi/polymetallic MOF-74 materials are rich in potential Lewis acidic active sites,which provide the possibility to improve electrochemical performance,especially as cathode materials for aqueous nickel-zinc batteries.In this paper,single-crystal ?-Ni(OH)2 and a series of Ni-MOF74-based composites were prepared by several different synthetic strategies,and their performance in aqueous Ni-Zn batteries was further investigated systematically.The main research work includes:1.Using a one-step hydrothermal method,the electrochemical performance differences of ?-Ni(OH)2 with different morphologies and sizes obtained with different reactant concentrations in aqueous nickel-zinc batteries were studied.The study found that the singlecrystal ?-Ni(OH)2 quasi-nanocubes obtained at high concentrations have smaller size and more(001)polar crystal planes,and the increase of active crystal planes and the improvement of electrical conductivity make their performance ideal areal specific capacity(0.34 mAh cm2 at 0.36 mA cm-2),ideal areal energy/power density(0.592 mWh cm-2,5.612 mW cm-2)and cycling stability(80.7%capacity retention after 500 cycles).2.Using a one-step solvothermal method,conductive carbon cloth(CC)was composited with MOF-74,and a series of Ni-MOF-74-based MOF-74 families were in-situ synthesized by a metal doping strategy utilizing the multi-metal synergistic effect,including monometallic Ni-MOF@CC,bimetallic NiM-MOF@CC(M=Mn2+,Co2+,Cu2+,Zn2+,Al3+,Fe3+)and multimetallic NiCoM-MOF@CC(M=Mn2+,Zn2+,Al3+,Fe3+).In addition,by adjusting the doping ratio of Co2+ ions without destroying the original topology,the optimized NiCoMOF@CC with a Co/Ni ratio of 1 exhibits high electrochemical stability(the retention rate after 6000 cycles is 83.0%),ideal specific capacity(1.77 mAh cm-2 at 5 mA cm-2)and high areal energy density(2.97 mWh cm-2).3.The introduction of amino acids into MOF materials can effectively adjust the electron distribution and charge density on the surface of the materials,and regulate the growth of MOFs to realize the modification of electrode materials.The amino-containing L-alanine was successfully introduced into Ni-MOF@CC and bimetallic NiCo-MOF@CC composites on carbon cloth by one-step solvothermal method.The study found that by adjusting the addition ratio of amino acids,when salicylic acid:L-alanine=2:1,ideal size and high stability can be obtained.Electrochemical test results show that the Ni1Co1-MOF@CC-N(NCM@CC-3-N)material has an ideal specific capacity(1.16 mAh cm-2 at 2 mA cm-2),while the Ni1Co0.25MOF@CC-N(NCM@CC-1-N)material has higher cycle stability(65.58%retention rate after 5000 cycles).