Synthesis And Electrochemical Properties Of Transition Metal Oxalate

As an important electrochemical energy storage device,reusable lithium-ion batteries have attracted great attention in various energy storage fields such as mobile phones,notebook computers,and new energy vehicles.At present,many fields are using graphite as a commercial lithium-ion battery material.Unfortunately,graphite only has a theoretical specific capacity of 372 m Ah g^-1.Therefore,there is a need to develop new anode materials for LIBs with high reversible capacity and stable cycle life.Due to the unique structure of the transition metal oxalate and the relatively strong electronegativity of oxalate,its application in the field of electrochemistry has gradually increased,which has also prompted more people to study its value.This article uses some simple synthesis methods to prepare transition metal oxalate materials with excellent electrochemical performance.The specific work is as follows:?1?By microwave-assisted methods,Cu C₂O₄·x H₂O materials?h Cu Ox?in hydrothermal state and Cu C₂O₄·x H₂O materials?s Cu Ox?in solvothermal state were prepared using deionized water and ethylene glycol as reaction media,respectively.Although,they have very similar XRD patterns.According to the results of thermogravimetric analysis,SEM and BET,they have many differences in crystallized water,morphology and average pore size.After the electrochemical performance test,the h Cu Ox and s Cu Ox electrodes showed a decrease in discharge specific capacity in the first four cycles.After 100 cycles,the discharge specific capacities were still 1064.3 m Ah g^-1and 939.3 m A h g^-1,respectively.?2?Fe C₂O₄ H₂O crystalizes in the orthorhombic space group Pbca?NO.61?with unit cell parameters a=6.1717?6??,b=9.5995?9??,c=115.1794?15??,?=90°,Z=8.The central atomic iron atom is coordinated by six oxygen atoms to form an octahedron,and the bond lengths are 2.3097?15???2.1759?14???2.1263?18???2.1344?15???2.0769?17??and 2.1259?19??,respectively.When the Fe C₂O₄ H₂O is used as the anode material,the initial discharge specific capacity is 1558.6 m Ah g^-1.Although the specific capacity continued to decrease in subsequent cycles,the specific capacity was 416.9 m Ah g^-1 after 100 cycles,which was still higher than commercial graphite(372 m Ah g^-1).?3?It is envisaged that the transition metal oxalate is compounded with ZIF-67,through the organic combination of MOF material organic framework structure,effectively slow down the process of charging and discharging of the volume expansion.By analyzing the results of XRD,SEM and other characterization methods,Ni C₂O₄/ZIF-67 has been successfully compounded.However,during the electrochemical test,it was found that the composite of Ni C₂O₄/ZIF-67 did not improve the electrochemical performance.It showed the initial specific discharge capacity of 888.6m Ah g^-1,the specific capacity is only 38.7 m Ah g^-1 after 100 cycles.Because of the characteristics of ZIF-67,Ni C₂O₄/ZIF-67 can obtain spinel material Ni Co₂O₄ with octahedral structure after roasting.After several improvement experiments,a double spinel Cu Co₂O₄-Ni Co₂O₄ composite was prepared.It has a specific initial discharge capacity of 1846.5 m Ah g^-1,and it still maintains 1330.1 m Ah g^-1 after 200 cycles.