Study On Aqueous Rechargeable Lithium-Ion Battery With High Energy Density

Aqueous Rechargeable Lithium-ion Battery?ARLB?is put forward because the system of traditional organic lithium ion battery are expensive and have poor safety performance.However,ARLB also has some defects such as low specific capacity and poor cycle performance.Therefore,these two major defects of ARLB restrict the development of high energy density ARLB.If ARLB is to achieve commercial production applications,it needs to improve its specific capacity,energy density and its cycle performance.In this paper,the positive electrode materials LiCoO₂ and LiMn₂O₄ are coated to improve their performance in ARLB,and Graphene Oxide?GO?and conductive polymer as the negative electrode materials of ARLB are also explored.?1?LiCoO₂ is synthesized by solid phase method,and is coated with GO,Polypyrrole?PPy?and Polyaniline?PANI?,respectively.All the materials are characterized by scanning electron microscope?SEM?,transmission electron microscope?TEM?and X-ray diffractometer?XRD?,and it is found that GO,PPy and PANI are coated on the surface of LiCoO₂,and there are characteristic peaks of the coating layer in the corresponding composite materials.Activated carbon?AC?is used as the negative electrode material to assemble the button cell to measure their electrochemical properties.The fitting results of the impedance diagram show that the impedance of the coated material decreases and the ion diffusion coefficient increases.Among the first charge and discharge curves under the current density of 0.1 A/g,the discharge capacity of LiCoO₂ is 65.24 mAh/g,and the discharge specific capacities of GO,PPy and PANI after cladding are 97.83 mAh/g,85.97 mAh/g and 87.04 mAh/g,respectively.At the current density of 0.8 A/g,the discharge specific capacity is only84%of that of original after 300 charging and discharging cycles of LiCoO₂//AC.After the coating of GO,PPy and PANI,the discharge specific capacity after 1000cycles can be maintained at 95%,90%and 92%,respectively.?2?LiMn₂O₄ is synthesized by solid phase method,and is coated with GO,PPy and PANI,respectively.All the materials are characterized by SEM,TEM and XRD,and it is found that GO,PPy and PANI are coated on the surface of LiMn₂O₄,and there are characteristic peaks of the coating layer in the corresponding composite materials.The fitting results of the impedance diagram show that the impedance of the coated material decreases and the ion diffusion coefficient increases.Among the first charge and discharge curves under the current density of 0.1 A/g,the discharge capacity of LiMn₂O₄ is 52.97 mAh/g,and the discharge specific capacities of GO,PPy and PANI after cladding are 93.03 mAh/g?75.01 mAh/g and 80.98 mAh/g,respectively.At the current density of 0.8 A/g,the discharge specific capacity is 86%of that of original after 1000 cycles of LiMn₂O₄//AC.After the coating of GO,PPy and PANI,the discharge specific capacity after 1000 cycles can be maintained at 92%,91%and 94%,respectively.?3?GO is synthesized by Hummers method,and PPy and PANI are synthesized by chemical oxidation method.AC,GO,PPy and PANI are characterized by SEM,TEM,XRD and FT-IR.LiNi_1/3Co_1/3Mn_1/3O₂ is used as positive electrode material to assemble the button cell to measure their electrochemical properties.As can be seen from the fitting results of impedance diagram,the impedance of AC is the largest,and the impedance of GO is the smallest.The impedance of PPy and PANI is smaller than that of AC.So LiNi_1/3Co_1/3Mn_1/3O₂//GO has the largest ion diffusion coefficient,and LiNi_1/3Co_1/3Mn_1/3O₂//AC has the smallest ion diffusion coefficient.Among the first charge and discharge curves under 0.1 A/g current density,the discharge specific capacities of AC,GO,PPy and PANI are 124.10 mAh/g,219.08 mAh/g,65.35 mAh/g and 71.01 mAh/g,respectively.Under the current density of 0.8 A/g,LiNi_1/3Co_1/3Mn_1/3O₂//GO,LiNi_1/3Co_1/3Mn_1/3O₂//PPy and LiNi_1/3Co_1/3Mn_1/3O₂//PANI have similar cycle performance after 1000 cycles of charging and discharging,and their discharge specific capacity are maintained at 83%,80%and 82%,respectively.The discharge capacity of LiNi_1/3Co_1/3Mn_1/3O₂//AC can only be maintained at 68%.The positive electrode materials are coated with GO,PPy and PANI,the specific capacity and energy density of ARLB can be improved,and the cycling performance of ARLB can also be improved.In contrast to AC,PPy and PANI,GO is excellent in both specific capacity and cycling performance,and can be used as a negative electrode material of ARLB with high energy density.