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Graphene wrapped ordered LiNi0.5Mn1.5O4 nanorods as promising cathode material for lithium-ion batteries.

Tang X, Jan SS, Qian Y, Xia H, Ni J, Savilov SV, Aldoshin SM - Sci Rep (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China [2] Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing 210094, China.

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.

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Related in: MedlinePlus

(a) Charge/discharge curves of the bare LiNi0.5Mn1.5O4 nanorod electrode at various cycle numbers at 0.1 C rate. (b) Charge/discharge curves of the LiNi0.5Mn1.5O4-graphene composite electrode at various cycle numbers at 0.1 C rate. (c) Comparison of cycle performance between the bare LiNi0.5Mn1.5O4 nanorod electrode and the LiNi0.5Mn1.5O4-graphene composite electrode. (d) Comparison of rate capability between the bare LiNi0.5Mn1.5O4 nanorod electrode and the LiNi0.5Mn1.5O4-graphene composite electrode.
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f8: (a) Charge/discharge curves of the bare LiNi0.5Mn1.5O4 nanorod electrode at various cycle numbers at 0.1 C rate. (b) Charge/discharge curves of the LiNi0.5Mn1.5O4-graphene composite electrode at various cycle numbers at 0.1 C rate. (c) Comparison of cycle performance between the bare LiNi0.5Mn1.5O4 nanorod electrode and the LiNi0.5Mn1.5O4-graphene composite electrode. (d) Comparison of rate capability between the bare LiNi0.5Mn1.5O4 nanorod electrode and the LiNi0.5Mn1.5O4-graphene composite electrode.

Mentions: Figure 8a,b show the charge/discharge curves of the bare LiNi0.5Mn1.5O4 nanorod and the LiNi0.5Mn1.5O4-graphene composite electrodes, respectively, at the 1st, 2nd, 50th, 100th, and 200th cycles at a current rate of 0.1 C between 3.0 and 4.9 V (vs. Li/Li+). Agreeing well with the CV results, the charge/discharge curves of the two electrodes clearly show only one flat voltage plateau around 4.70 V (vs. Li/Li+) due to the Ni2+/Ni4+ redox couple, which is the characteristic electrochemical behavior of the ordered spinel8. In comparison, the charge/discharge curves of the LiNi0.5Mn1.5O4-graphene composite electrode show much smaller voltage difference between charge and discharge voltage plateaus, indicating smaller polarization and internal resistance of the spinel electrode with graphene incorporation. The first charge and discharge capacities of the LiNi0.5Mn1.5O4-graphene composite electrode are 127.6 and 122.4 mAh g−1, with a coulombic efficiency of about 96%. By contrast, the first charge and discharge capacities of the bare LiNi0.5Mn1.5O4 nanorod electrode are 127.3 and 119.7 mAh g−1, respectively, with a coulombic efficiency of about 94%. It is clear that the LiNi0.5Mn1.5O4-graphene composite electrode can deliver a larger reversible capacity and higher coulombic efficiency compared to the bare LiNi0.5Mn1.5O4 nanorod electrode. The larger reversible capacity of the LiNi0.5Mn1.5O4-graphene composite electrode can be attributed to the smaller polarization of the electrode, which favors fast charge transport and increases the utilization of the active material. The initial irreversible capacity loss is partially contributed by the solid electrolyte interface (SEI) layer formation due to the electrolyte decomposition at high voltage31. The wrapping with graphene could greatly suppress the SEI layer formation at high voltage, thus improving the initial coulombic efficiency of the composite electrode. Figure 8c compares the cycle performance of the two electrodes, revealing greatly improved cycling stability for the LiNi0.5Mn1.5O4-graphene composite electrode. After 200 cycles at 0.1 C rate, LiNi0.5Mn1.5O4-graphene composite electrode can still deliver a reversible capacity of about 115 mAh g−1, retaining 94% of its initial reversible capacity. In comparison, the bare LiNi0.5Mn1.5O4 nanorod electrode only retained 82% of its initial reversible capacity. The capacity fading of the high voltage spinel during cycling is mainly contributed by the structural deterioration induced by Mn3+ ion dissolution and internal resistance increase induced by the side reactions at the electrode surface at high voltage3233. For the ordered spinel, Mn3+ ion dissolution may not be the major reason that causes the capacity fading since there are negligible Mn3+ ions in ordered spinel due to its nearly perfect stoichiometry. The side reactions, including SEI layer formation, could be more detrimental to the cycle performance because the increased polarization induced by the increasing resistance will lead to less reversible capacity. As shown in Fig. 8a, the voltage difference between charge and discharge keeps increasing with the cycling test, revealing a obvious cell polarization growth for the bare LiNi0.5Mn1.5O4 nanorod electrode. By contrast, the polarization growth for the LiNi0.5Mn1.5O4-graphene composite electrode is greatly mitigated, which can be attributed to the graphene protection, suppressing the side reactions at the electrode surface. Figure 8d compares the rate capability of the two electrodes by plotting the specific capacity as a function of cycle number at different current rates. The typical charge/discharge curves of bare LiNi0.5Mn1.5O4 nanorod electrode and the LiNi0.5Mn1.5O4-graphene composite electrode at different current rates are shown in Fig. S3 (Supporting Information). It is obvious that the LiNi0.5Mn1.5O4-graphene composite electrode possesses much better rate capability as it can retain more reversible capacity as the discharge rate increases. Even at 10 C rate, the LiNi0.5Mn1.5O4-graphene composite electrode can still deliver a reversible capacity of about 80.8 mAh g−1, which is much larger than that of the bare LiNi0.5Mn1.5O4 nanorod electrode (49.2 mAh g−1). When the current rate was set back to 0.1 C, the charge and discharge capacities of LiNi0.5Mn1.5O4-graphene composite electrode recover to the original values, indicating that large current density and rapid lithiation/delithiation did not cause any permanent damage to the crystal structure. However, after the bare LiNi0.5Mn1.5O4 nanorod electrode experienced the high current rate like 10 C, its reversible capacity didn't fully recover to the initial value when the current rate was changed back to 0.1 C. The superior rate performance of the LiNi0.5Mn1.5O4-graphene composite electrode can be attributed to the improved electron transport provided by the graphene conductive matrix. As confirmed by the EIS measurements, the LiNi0.5Mn1.5O4-graphene composite electrode shows much smaller charge transfer resistance compared to the bare LiNi0.5Mn1.5O4 nanorod electrode, indicating the graphene wrapping is beneficial to fast electrode kinetics (Fig. S4, Supporting Information).


Graphene wrapped ordered LiNi0.5Mn1.5O4 nanorods as promising cathode material for lithium-ion batteries.

Tang X, Jan SS, Qian Y, Xia H, Ni J, Savilov SV, Aldoshin SM - Sci Rep (2015)

(a) Charge/discharge curves of the bare LiNi0.5Mn1.5O4 nanorod electrode at various cycle numbers at 0.1 C rate. (b) Charge/discharge curves of the LiNi0.5Mn1.5O4-graphene composite electrode at various cycle numbers at 0.1 C rate. (c) Comparison of cycle performance between the bare LiNi0.5Mn1.5O4 nanorod electrode and the LiNi0.5Mn1.5O4-graphene composite electrode. (d) Comparison of rate capability between the bare LiNi0.5Mn1.5O4 nanorod electrode and the LiNi0.5Mn1.5O4-graphene composite electrode.
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f8: (a) Charge/discharge curves of the bare LiNi0.5Mn1.5O4 nanorod electrode at various cycle numbers at 0.1 C rate. (b) Charge/discharge curves of the LiNi0.5Mn1.5O4-graphene composite electrode at various cycle numbers at 0.1 C rate. (c) Comparison of cycle performance between the bare LiNi0.5Mn1.5O4 nanorod electrode and the LiNi0.5Mn1.5O4-graphene composite electrode. (d) Comparison of rate capability between the bare LiNi0.5Mn1.5O4 nanorod electrode and the LiNi0.5Mn1.5O4-graphene composite electrode.
Mentions: Figure 8a,b show the charge/discharge curves of the bare LiNi0.5Mn1.5O4 nanorod and the LiNi0.5Mn1.5O4-graphene composite electrodes, respectively, at the 1st, 2nd, 50th, 100th, and 200th cycles at a current rate of 0.1 C between 3.0 and 4.9 V (vs. Li/Li+). Agreeing well with the CV results, the charge/discharge curves of the two electrodes clearly show only one flat voltage plateau around 4.70 V (vs. Li/Li+) due to the Ni2+/Ni4+ redox couple, which is the characteristic electrochemical behavior of the ordered spinel8. In comparison, the charge/discharge curves of the LiNi0.5Mn1.5O4-graphene composite electrode show much smaller voltage difference between charge and discharge voltage plateaus, indicating smaller polarization and internal resistance of the spinel electrode with graphene incorporation. The first charge and discharge capacities of the LiNi0.5Mn1.5O4-graphene composite electrode are 127.6 and 122.4 mAh g−1, with a coulombic efficiency of about 96%. By contrast, the first charge and discharge capacities of the bare LiNi0.5Mn1.5O4 nanorod electrode are 127.3 and 119.7 mAh g−1, respectively, with a coulombic efficiency of about 94%. It is clear that the LiNi0.5Mn1.5O4-graphene composite electrode can deliver a larger reversible capacity and higher coulombic efficiency compared to the bare LiNi0.5Mn1.5O4 nanorod electrode. The larger reversible capacity of the LiNi0.5Mn1.5O4-graphene composite electrode can be attributed to the smaller polarization of the electrode, which favors fast charge transport and increases the utilization of the active material. The initial irreversible capacity loss is partially contributed by the solid electrolyte interface (SEI) layer formation due to the electrolyte decomposition at high voltage31. The wrapping with graphene could greatly suppress the SEI layer formation at high voltage, thus improving the initial coulombic efficiency of the composite electrode. Figure 8c compares the cycle performance of the two electrodes, revealing greatly improved cycling stability for the LiNi0.5Mn1.5O4-graphene composite electrode. After 200 cycles at 0.1 C rate, LiNi0.5Mn1.5O4-graphene composite electrode can still deliver a reversible capacity of about 115 mAh g−1, retaining 94% of its initial reversible capacity. In comparison, the bare LiNi0.5Mn1.5O4 nanorod electrode only retained 82% of its initial reversible capacity. The capacity fading of the high voltage spinel during cycling is mainly contributed by the structural deterioration induced by Mn3+ ion dissolution and internal resistance increase induced by the side reactions at the electrode surface at high voltage3233. For the ordered spinel, Mn3+ ion dissolution may not be the major reason that causes the capacity fading since there are negligible Mn3+ ions in ordered spinel due to its nearly perfect stoichiometry. The side reactions, including SEI layer formation, could be more detrimental to the cycle performance because the increased polarization induced by the increasing resistance will lead to less reversible capacity. As shown in Fig. 8a, the voltage difference between charge and discharge keeps increasing with the cycling test, revealing a obvious cell polarization growth for the bare LiNi0.5Mn1.5O4 nanorod electrode. By contrast, the polarization growth for the LiNi0.5Mn1.5O4-graphene composite electrode is greatly mitigated, which can be attributed to the graphene protection, suppressing the side reactions at the electrode surface. Figure 8d compares the rate capability of the two electrodes by plotting the specific capacity as a function of cycle number at different current rates. The typical charge/discharge curves of bare LiNi0.5Mn1.5O4 nanorod electrode and the LiNi0.5Mn1.5O4-graphene composite electrode at different current rates are shown in Fig. S3 (Supporting Information). It is obvious that the LiNi0.5Mn1.5O4-graphene composite electrode possesses much better rate capability as it can retain more reversible capacity as the discharge rate increases. Even at 10 C rate, the LiNi0.5Mn1.5O4-graphene composite electrode can still deliver a reversible capacity of about 80.8 mAh g−1, which is much larger than that of the bare LiNi0.5Mn1.5O4 nanorod electrode (49.2 mAh g−1). When the current rate was set back to 0.1 C, the charge and discharge capacities of LiNi0.5Mn1.5O4-graphene composite electrode recover to the original values, indicating that large current density and rapid lithiation/delithiation did not cause any permanent damage to the crystal structure. However, after the bare LiNi0.5Mn1.5O4 nanorod electrode experienced the high current rate like 10 C, its reversible capacity didn't fully recover to the initial value when the current rate was changed back to 0.1 C. The superior rate performance of the LiNi0.5Mn1.5O4-graphene composite electrode can be attributed to the improved electron transport provided by the graphene conductive matrix. As confirmed by the EIS measurements, the LiNi0.5Mn1.5O4-graphene composite electrode shows much smaller charge transfer resistance compared to the bare LiNi0.5Mn1.5O4 nanorod electrode, indicating the graphene wrapping is beneficial to fast electrode kinetics (Fig. S4, Supporting Information).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China [2] Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing 210094, China.

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.

No MeSH data available.


Related in: MedlinePlus