Abstract
LiNi0.5Mn1.5O4 nanorods wrapped with graphene nanosheets have been prepared and investigated as high energy and high power cathode material for lithium-ion batteries. The structural characterization by X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy indicates the LiNi0.5Mn1.5O4 nanorods prepared from β-MnO2 nanowires have ordered spinel structure with P4332 space group. The morphological characterization by scanning electron microscopy and transmission electron microscopy reveals that the LiNi0.5Mn1.5O4 nanorods of 100–200 nm in diameter are well dispersed and wrapped in the graphene nanosheets for the composite. Benefiting from the highly conductive matrix provided by graphene nanosheets and one-dimensional nanostructure of the ordered spinel, the composite electrode exhibits superior rate capability and cycling stability. As a result, the LiNi0.5Mn1.5O4-graphene composite electrode delivers reversible capacities of 127.6 and 80.8 mAh g−1 at 0.1 and 10 C, respectively, and shows 94% capacity retention after 200 cycles at 1 C, greatly outperforming the bare LiNi0.5Mn1.5O4 nanorod cathode. The outstanding performance of the LiNi0.5Mn1.5O4-graphene composite makes it promising as cathode material for developing high energy and high power lithium-ion batteries.
Highlights
LiNi0.5Mn1.5O4 nanorods wrapped with graphene nanosheets have been prepared and investigated as high energy and high power cathode material for lithium-ion batteries
The hydrothermally prepared β -MnO2 nanowires were used as the template and the X-ray diffraction (XRD) pattern shows no trace of impurity (Fig. S1, Supporting Information)
The as-synthesized LiNi0.5Mn1.5O4 nanorods and the LiNi0.5Mn1.5O4-graphene composite show similar XRD patterns, which can be indexed to the cubic spinel structure with space group P4332 (JCPDS No 80-2184)
Summary
LiNi0.5Mn1.5O4 nanorods wrapped with graphene nanosheets have been prepared and investigated as high energy and high power cathode material for lithium-ion batteries. The outstanding performance of the LiNi0.5Mn1.5O4-graphene composite makes it promising as cathode material for developing high energy and high power lithium-ion batteries. To further increase the energy density for lithium-ion batteries, various positive electrode materials have been widely investigated to obtain either high working voltage or large capacity. The increased surface area associated with nanostructuring will aggravate the side reactions at high voltage and deteriorate the capacity fading during cycling Another approach people often used is to modify the spinel surface by coating a thin protective layer, which can greatly improve the interface stability with enhanced cycling performance[16,17,18,19,20]. New strategies that can combine the advantages of the above mentioned two approaches need to be developed to further improve the electrochemical performance of the high voltage spinels
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