Research On The Construction And Performance Improvement Of Next-Generation Fe-Ni Battery Anode Materials

With the increasing demand for energy in human society,the consumption of non-renewable resources such as oil and natural gas is increasing,and environmental problems are becoming increasingly prominent.Therefore,the research on efficient and environmentally friendly energy storage devices has become a global research hotspot.As an alkaline water battery,Ni-Fe battery was first invented in 1901.It has advantages of environmental friendliness,high theoretical capacity,wide sources of raw materials,resistance to mechanical damage and resistance to overcharge and overdischarge,so it once became a hot research object.However,the anode materials encounter a large volume change during the discharge process,and passivation occurs during the discharge process.In addition to that,due to the low hydrogen evolution overvoltage of iron,the hydrogen evolution reaction occurs during the charging process,which affects the rate performance and cycle stability of the iron-nickel battery.To solve the above problems,mesoporous structure have been introduced into micron-sized Fe₃O₄ particles to improve the rate performance and cycle stability of Ni-Fe batteries.Besides,we research the electrochemical performance of ferroferric oxide（Fe₃O₄）anode materials with different crystallization degrees to explore the influence of the degree of crystallization on the electrochemical performance of Ni-Fe batteries.The specific contents are as follows:（1）Through a facile etching method,the mesoporous structure was introduced into the micron-sized Industrial Fe₃O₄.The introduced mesoporous Fe₃O₄ sheets exist around the micron-sized Fe₃O₄ particles.They can transfer the hydrogen generated on the surface of the micron-sized particles in time to expose the active sites on the surface.They can also alleviate the volume change of the micron-sized Fe₃O₄particles during the discharge process.Compared with Industrial Fe₃O₄ and carbon-coated modified Fe₃O₄,its capacity,rate performance and cycle stability have been greatly improved.At the discharge rate of 0.2 A g^-1,its capacity is 221.17 m Ah g^-1,which is 1.8 times the capacity of Industrial Fe₃O₄.When it was assembled with cathode to form full battery,the full battery also displayed the excellent performance,demonstrating its great application potential.In addition,the etching method in this work is simple,which can be easily applied into Industrial production.This work not only gives a new modification method for the anode materials of Ni-Fe batteries,but also provides a reference strategy for the improvement of the Ni-Fe battery anode materials.（2）We research the effect of the crystallinity of the iron anode material of the Ni-Fe battery on the electrochemical performance.The Fe₃O₄ with better conductivity was selected as the research object.Then Fe₃O₄ anode materials with the same morphology but different degrees of crystallinity were synthesized and their electrochemical performance was tested.The results show that improving the degree of crystallinity can enhance the rate performance and cycling stability of the anode.This may be due to that increasing the degree of crystallinity could enhance the charge transfer process and then improves the charge transfer rate.On the other hand,Fe₃O₄ with improved degree of crystalinity can enhance the suppression to hydrogen evolution,reduce the hydrogen adsorbed on the surface of the particles to enhance ion transportation,and reduce the damage to the material structure during the cycling process.This work conducts a preliminary research of the influence of the degree of crystallinity of the iron anode on the electrochemical performance,and provides a reference for the further improvement of the iron anode material in the future.