Abstract
A carbon nanotubes/graphene composite is grown on nickel foil without additional catalysts by one-step ambient pressure chemical vapor deposition (CVD). Next, the carbon nanotubes/graphene composite is modified by radio frequency (RF) nitrogen plasma. Finally, to improve its initial coulombic efficiency/electrochemical stability, lower potential during the charge process (coin cell), and boost potential during the discharge process (lithium-ion battery), alumina is deposited onto the N-doped carbon nanotubes/graphene composite by RF magnetron sputtering at different power levels and periods of time. The charge specific capacity (597 mAh/g) and initial coulombic efficiency (81.44% > 75.02% for N-doped carbon nanotubes/graphene) of Al2O3/N-doped CNTs/graphene for the coin cell reached a maximum at the best sputtering condition ( power = 65 W and time = 30 min ). Al2O3/N-doped CNTs/graphene (the best sputtering condition) exhibits higher initial coulombic efficiency (79.8%) compared with N-doped CNTs/graphene (initial coulombic efficiency: 74.3%) for the lithium-ion battery. Furthermore, the achievement fraction (about 70%) of full charge capacity (coin cell) for Al2O3/N-doped carbon nanotubes/graphene (the best sputtering condition) is higher than that (about 30%) for N-doped carbon nanotubes/graphene at a voltage lower than about 0.25 V. Moreover, it also shows a little higher electrochemical stability (coin cell) of charge capacity for Al2O3/N-doped carbon nanotubes/graphene (the best sputtering condition) in comparison with N-doped carbon nanotubes/graphene and Al2O3/N-doped CNTs/graphene (the best sputtering condition) exhibits better cyclic stability (lithium-ion battery) of discharge capacity compared with N-doped CNTs/graphene.
Highlights
The applications of lithium-ion batteries include portable electronic devices, electric vehicles, and hybrid electric vehicles
chemical vapor deposition (CVD) was used to simultaneously synthesize carbon nanotubes (CNTs) as well as graphene on nickel foam without additional catalysts at 800°C and the carbon nanotubes/graphene composite was modified by radio frequency (RF) nitrogen plasma treatment
Alumina was deposited onto the N-doped carbon nanotubes/graphene composite by RF magnetron sputtering at different power levels and periods of time in this study
Summary
The applications of lithium-ion batteries include portable electronic devices, electric vehicles, and hybrid electric vehicles. CVD was used to simultaneously synthesize carbon nanotubes (CNTs) as well as graphene on nickel foam without additional catalysts at 800°C and the carbon nanotubes/graphene composite was modified by RF nitrogen plasma treatment. It still possessed lower initial coulombic efficiency/electrochemical stability and mainly occurred higher potential during the charge process of the coin cell as well as lower potential during the discharge process of the lithium-ion battery for the N-doped carbon nanotubes/graphene composite. To improve its initial coulombic efficiency/electrochemical stability, lower potential during the charge process of the coin cell, and enhance potential during the discharge process of the lithium-ion
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