Synthsis And Research Of High-Performance Alkaline Secondry Batteries Iron-Based Anode Materials

The energy and environmental issues has become increasingly prominent in the twenty-first century,countries are looking for new energy that is efficient and environmentally friendly.The traditional iron-nickel batteries?Commonly known as the "Edison battery"?because of its safety,environmental protection,long cycle life,low cost,high theoretical capacity,resistant to over charge and discharge,etc and again aroused people's concern.But iron-nickel battery still exists easy passivation,serious gas evolution,low charging efficiency and poor high-rate performance problems,and these to some extent restricts its application.In this paper in view of the problems existing in the iron nickel battery,on the basis of predecessors' research,mainly carried out the following work:?1?FeS and its composite,FeS/C,are synthesized via a simple calcination method followed by a co-precipitation process.The electrochemical properties of the bare FeS and FeS/C composite as anode materials for alkaline nickeleiron batteries are investigated.The results show that the FeS/C-3wt%Bi2O3-mixed electrode delivers a high specific capacity of 325 mAhg^-1at a current density of 300 mAg^-1 with a faradaic efficiency of 90.3% and retains 99.2% of the initial capacity after 200 cycles.For the first time,it is demonstrated that even at a discharge rate as high as 1500 mAg^-1?5C?the FeS/C-3wt%Bi2O3-mixed electrode delivers a specific capacity of nearly 230 mAhg^-1.SEM results confirm that after 200 discharge-charge cycles,the size of FeS/C particles reduces from 5 to 15 mm to less than 300 nm in diameter and the particles are highly dispersed on the surface of carbon black,which is likely caused by the dissolution-deposition process of Fe?OH?₂ and Fe via intermediate iron species.As a result,the FeS/C composite exhibits considerably high charge efficiency,high discharge capacities,excellent rate capability and superior cycling stability.We believe that this composite is a potential candidate of high performance anode materials for alkaline iron-based rechargeable batteries.?2?High-performance Fe₃O₄ polyhedrons as alkaline secondary battery anode materials have successfully been synthesized using a facile co-precipitation method with a subsequent annealing treatment at 700?C for 1 h.The physical and electrochemical properties of the Fe₃O₄ samples annealed at different temperatures are investigated.It has been discovered that the annealing temperature plays a vital role in improving the physical and electrochemical performances of the Fe₃O₄ materials.The results also indicate that the Fe₃O₄ sample annealed at 700?C performs better?faster activation rate,higher specific discharge capacity,better high-rate ability and cycle stability?than the samples annealed at other temperatures.The specific discharge capacity of the 700?C-annealed Fe₃O₄ reaches 604.2mAh g^-1at a current density of 120 mAg^-1with a charging efficiency of 83.9%.Moreover,discharge capacities of 587.6,539.5 and 500.1 mAh g^-1are achieved at 240,600 and 1200 mAg^-1,respectively,exhibiting remarkable high-rate discharge capability.This performance improvement may be attributable to better reaction reversibility,lower charge transfer impedance and better inhibiting effect on hydrogen evolution reaction of the material.We believe that this Fe₃O₄ polyhedron is a promising candidate as the anode material for high-performance alkaline secondary batteries.?3?A new type of graphene-based Fe₃O₄ composite have been synthesized by a simple calcination method followed by a co-precipitation process.The electrochemical properties of the bare Fe₃O₄ and Fe₃O₄/RGO composite as anode materials for alkaline nickel-iron batteries are investigated.When evaluated as anode material for the alkaline nickel-iron battery,the Fe₃O₄/RGO composite deliver a high specific capacity of 623 mAhg^-1 at a current density of 120 mAg^-1.Furthermore,Fe₃O₄ composite undergo only 15% capacity decay when the discharge current density is changed from 1200 mAg^-1 to 12000 mAg^-1.Compared with bare Fe₃O₄,the discharge capacity and high rate capability of Fe₃O₄/RGO composite is better.The enhanced discharge capacity and high rate capability derives from the high specific surface area of Fe₃O₄ particles and particular electric conductivity of graphene.We believe that this composite is a potential candidate of high performance anode materials for alkaline iron-based rechargeable batteries.