3O2 Nanosheet Cathode with High

Research Article Cite This: ACS Appl. Mater. Interfaces 2017, 9, 39560-39568

www.acsami.org

Self-Assembled LiNi1/3Co1/3Mn1/3O2 Nanosheet Cathode with High Electrochemical Performance Hao Zheng,†,‡ Xiao Chen,† Yun Yang,† Lin Li,‡ Guohua Li,§ Zaiping Guo,†,∥ and Chuanqi Feng*,† †

Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University, Wuhan 430062, China Key Laboratory of Functional Materials and Chemistry for Performance and Resources of Guizhou Education Department, Anshun University, Anshun 561000, China § School of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032, China ∥ Institute for Superconducting & Electronic Materials, University of Wollongong, Wollongong, NSW 2522, Australia ‡

S Supporting Information *

ABSTRACT: We have fabricated self-assembled LiNi1/3Co1/3Mn1/3O2 nanosheets via a facile synthesis method combining coprecipitation with the hydrothermal method. Scanning electron microscopic images show that the selfassembly processes for the LiNi1/3Co1/3Mn1/3O2 nanosheets depend on the reaction time and temperature. The nanosheet structure is uniform, and the width and thickness of the nanosheets are in the ranges of 0.7−1.5 μm and 10−100 nm, respectively. As a cathode material, the as-synthesized LiNi1/3Co1/3Mn1/3O2 nanosheets have demonstrated outstanding electrochemical performance. The initial specific capacity was 193 mAh g−1, and the capacity was maintained at 189 mAh g−1 after 100 cycles at 0.2 C, and 155 mAh g−1 at 1 C (after 1000 cycles). The LiNi1/3Co1/3Mn1/3O2 nanosheets have efficient contact with the electrolyte and short Li+ diffusion paths, as well as sufficient void spaces to accommodate large volume variation. The nanosheets are thus beneficial to the diffusion of Li+ in the electrode. The enhanced electrical conductance and excellent capacity demonstrate the great potential of LiNi1/3Co1/3Mn1/3O2 nanosheets for energy storage applications. KEYWORDS: LiNi1/3Co1/3Mn1/3O2, nanosheets, self-assembled, cathode material, lithium-ion batteries

■

delivered a superior specific capacity, 1051 mAh g−1 at the rate of 0.5 A g−1 after 100 cycles. The hybrid nanoarchitecture possessed a large surface area, abundant electron/lithium pathways, and high porosity. Hu and co-workers16 reported that TiO2-B nanosheet arrays showed high capacity and good cycling stability and rate capability. Compared with anode materials, enormous work has been conducted on nanosheet structured cathode materials (such as LiMn 2 O 4 , V 2 O 5 , Li x V 3 O 8 , LiFePO 4 , Li 2 MSiO 4 , LiNi1/3Co1/3Mn1/3O2, etc.).17−25 Yuan et al.26 found that nanoporous LiMn 2O4 nanosheet electrodes exhibited higher durability compared to the corresponding bulk material, which is attributed to their two-dimensional (2D) structure, short diffusion lengths, high crystallinity, and exposed {111} facets. Wang et al.27 reported that Li1.5V3O8 nanosheets featured a high discharge specific capacity (204 mAh g−1 at current density of 175 mA g−1) and long cycling stability due to their nanosheet structure, which can provide a large surface area and full contact with the electrolyte. The as-synthesized LiMPO4 nanosheets

INTRODUCTION In modern times, rechargeable Li-ion batteries (LIBs) have been universally used in plug-in electric vehicles and portable electronics, owing to their advantages of high energy density and long life.1,2 Tremendous efforts have been committed to the development of nanostructured electrode materials (such as nanoplates, nanoarrays, nanobelts, nanorods, nanosheets, nanowires, and nanotubes) to improve the electrochemical performance of LIBs because they can offer excellent chemical and physical properties and have promising applications in energy storage owing to their large surface-to-volume ratio and fast lithium-ion diffusion.3−6 The nanoscale morphologies (e.g., nanoplates and nanosheets) have the advantages of shorter Li+ diffusion distances, larger active surface area, and stable structures.7−9 An abundance of anode materials with the nanosheet structure (such as MoS2, MnOx, MoOx, ZnCo2O4, etc.) have been reported that exhibit outstanding electrochemical performance10−12 because the unique nanosheet structure can offer a large contact surface, easy insertion/ extraction of ions, and short transfer distance of Li ions.13,14 Ni et al.15 synthesized ultrathin MoO2 nanosheets through interfacial self-assembly and a reduction reaction using glucose. The MoO2/C nanosheets © 2017 American Chemical Society

Received: July 20, 2017 Accepted: October 16, 2017 Published: October 16, 2017 39560

DOI: 10.1021/acsami.7b10264 ACS Appl. Mater. Interfaces 2017, 9, 39560−39568

Research Article

ACS Applied Materials & Interfaces have demonstrated the features of good electronic conductivity, lithium diffusion in the [010] direction, miniscule atomic-scale thicknesses, and high contact area.28 Nanostructured LiNi1/3Co1/3Mn1/3O2 materials have enormous application potential because they can overcome low packing density and poor consistency.29 Yu et al.30 reported LiNi1/3Co1/3Mn1/3O2 nanosheets synthesized by a facile hydrothermal method and calcination process. The exposed {010} facets had a major influence on their cycling stability and rate capability. LiNi1/3Co1/3Mn1/3O2 hexagonal nanobricks were prepared by a precursor−template method.31 The LiNi1/3Co1/3Mn1/3O2 hexagonal nanobricks showed excellent cycling stability with fast Li+ intercalation and deintercalation. Hua and co-workers32 developed a large-scale synthesis method for LiNi1/3Co1/3Mn1/3O2 nanoflowers. Their LiNi1/3Co1/3Mn1/3O2 nanoflowers provide fast transport of Li+ and electrons due to the flower-like nanoarchitecture. Li et al.33 reported 2D hierarchical LiNi1/3Co1/3Mn1/3O2 nanosheets that were synthesized by a simple sol−gel method. The product showed excellent electrochemical performance, which might be improved by adjusting the thickness of the nanosheets. Pi et al.34 reported that their disk-like LiNi1/3Co1/3Mn1/3O2 nanoplates displayed excellent capacity. Herein, self-assembled LiNi1/3Co1/3Mn1/3O2 nanosheets were synthesized via a facile coprecipitation method combined with a hydrothermal approach. The morphology of the products can be easily tuned by adjusting the reaction temperature and time. Benefitting from the combined advantages of LiNi1/3Co1/3Mn1/3O2 nanosheets (fast pseudocapacitive behavior, large surface area, reduced ion-diffusion length, high electrical conductivity, and excellent stability) as the cathode material, the LiNi1/3Co1/3Mn1/3O2 nanosheet electrode displays excellent electrochemical performance.

■

EXPERIMENTAL SECTION

Synthesis of LiNi1/3Co1/3Mn1/3O2 Nanosheets. Typically, 1.0 g of cetyltrimethylammonium bromide (CTAB) and 10 mmol each of MnCl2·4H2O, NiCl4·4H2O, and CoCl4·4H2O were added into a 20 mL mixed solution of water and ethanol (1:1 by volume) (designated as the A solution). CTAB (2.0 g), NaHCO3 (20 mmol), and NH4HCO3 (2.0 mmol) were added into a 200 mL mixed solution of water and ethanol (1:1 by volume) (designated as the B solution). After magnetic stirring at room temperature for 1 h, two water-in-oil microemulsions were formed. The feedstock in container A was then introduced into container B under continuous stirring. After reaction for 2 h, the asprepared products were cleaned with H2O and ethanol and dried at 60 °C for 5 h. LiOH·H2O (0.10 g) and the as-prepared precursor (0.15 g) were added into a Teflon container with 10 mL of 12 mol·L−1 KOH solution. After heating the above solution at 180 °C for 12 h, the black precipitates were washed with H2O and ethanol and dried at 60 °C to obtain the final products (designated as NCM-180). Detailed information on the characterization of materials and electrochemical measurements can be found in the Supporting Information.

Figure 1. (a) XRD pattern and (b) Raman spectrum of NCM-180 nanosheets.

indicates the presence of Ni2+ ions migrating in to the Li layers. The exact ratio of Mn/Co/Ni (0.98:0.96:0.95) was measured by inductively coupled plasma-atomic emission spectroscopy (ICPAES) for the sample (Table S1 in the Supporting Information). The structural features of the LiNi1/3Co1/3Mn1/3O2 nanosheets were further confirmed by Raman measurements. As shown in Figure 1b, we can clearly see that there are strong peaks in the spectral range from 300 to 650 cm−1 for the NCM-180 sample. Figure 1b shows bands at 478 and 556 cm−1 (Ni−O) and at 485 and 598 cm−1 (Co−O) that represent the vibrations within the hexagonal MO2 (M = metal) lattice. The sample shows a strong wide peak at approximately 609 cm−1, which is assigned to the Mn−O stretching vibration of MnO6 octahedra.35,36 In addition, X-ray photoelectron spectroscopy (XPS) measurements were used to confirm the oxidation states of Ni, Co, Mn, and O in NCM-180, as shown in Figure 2. The Ni 2p XPS spectrum in Figure 2b consists of Ni 2p3/2 (852.16 eV), Ni 2p1/2 (871.96 eV), and two characteristic broad satellite peaks with the binding energies at 861.09 and 879.71 eV, indicating that there is a slight amount of Ni2+ in the samples.30,32 The binding energy values of the Mn 2p3/2 peak at 641.12 and 654.10 eV are typical for the Mn4+ oxidation state. The Co 2p3/2 energy at 779.94 eV confirms the Co3+ oxidation states in the material.

■

RESULTS AND DISCUSSION The crystallinity and phase purity were examined from the X-ray diffraction (XRD) patterns. Figure 1a shows the XRD pattern of the NCM-180 sample. The characteristic peaks (006)/(102) and (108)/(110) of the NCM-180 sample suggested the formation of the hexagonal α-NaFeO2 structure30 without any impurity phase. The peak intensity ratio of I(003)/I(104) is 1.42, so low cation mixing is manifested in this sample.29,31 In addition, it 39561


Research Article

ACS Applied Materials & Interfaces

Figure 2. (a) XPS survey spectrum of NCM-180 and high-resolution XPS spectra of (b) Ni 2p, (c) Co 2p, and (d) Mn 2p.

nanoflakes and mainly nanoparticles due to the lower interfacial nucleation energy on the surface of LiNi1/3Co1/3Mn1/3O2 (as shown in Figure 4a). Figure 4b shows the morphology of the LiNi1/3Co1/3Mn1/3O2 nanostructures grown at 140 °C. The SEM image demonstrates that the as-obtained products are mainly nanoflakes. When the synthesis process was implemented at a higher temperature (160 °C), large and uniform LiNi1/3Co1/3Mn1/3O2 nanosheets were obtained (Figure 4c). Figure 4d shows the XRD patterns of the samples synthesized at different temperatures (120, 140, and 160 °C). For all kinds of self-assembled NCM structures, all of the peaks suggest the formation of the hexagonal α-NaFeO2 structure30 without any impurity phase. For the XRD patterns of the 140 and 160 °C samples, the (003) to (104) peak ratios were 1.28 and 1.35, respectively (larger than 1.2), but the intensity ratio of the (003) to the (104) peak of the 120 °C sample (1.18) was below 1.2. The evolution of the morphology of the NCM-180 nanosheets was examined in terms of the reaction time using SEM images (Figure 5). It can be seen that after a reaction time for 1 h, the microparticles began to be pulverized, forming a number of submicron particles with sizes of about 200 nm. Careful observation of the image (Figure 5a) shows that tiny nanosheets coexist with the nanoparticles for hydrothermal treatment for 1 h in 12 mol·L−1 KOH solution. After hydrothermal treatment for 3 h, more nanosheets start to form and coexist with the nanoparticles (Figure 5b). After 6 h of reaction, the SEM

Analysis of the metal ion contents from XPS also suggests that the molar ratios of the metal elements in the prepared samples are in good agreement with their stoichiometric proportions. (The exact ratio of Mn/Co/Ni is 0.98:0.96:0.95.) The morphology and structure of the NCM-180 sample was characterized by scanning electron microscopy (SEM). As shown in Figure 3a,b, the sample has a uniform nanosheet structure, and the width and thickness of the nanosheets are in the ranges of 0.7−1.5 μm and 10−100 nm, respectively. It is clear that even the relatively thicker nanosheets are thin structures (in the range of tens of nanometers). Energy-dispersive spectroscopy (EDS) mapping analysis was carried out as shown in Figure 3c. The Ni, Co, Mn, and O elements were uniformly dispersed throughout the whole region of the particle. The transmission electron microscopic (TEM) images (Figure 3d,e) show that the NCM180 nanosheet sample is composed of layered structures. The high-resolution TEM (HRTEM) image (Figure 3e) taken from the edge of the nanosheet shows the lattice fringe spacing of 0.247 nm (conforming to the interplanar spacing of (010) lattice planes). To further investigate the effects of the molar ratio of Ni/Co/Mn, the EDS spectrum was collected. The molar ratio of Ni/Co/Mn is around 1:1:1, as shown in Figure S1 and Table S2. The evolution process for LiNi1/3Co1/3Mn1/3O2 nanostructures with different hydrothermal synthesis temperatures was investigated, as shown in Figure 4. With a lower reaction temperature of 120 °C, the as-obtained products were disordered 39562


Research Article


Figure 3. (a, b) Typical field emission SEM images, (c) EDS mapping analysis, and (d, e) HRTEM images of NCM-180.

LiNi1/3Co1/3Mn1/3O2 nanosheets involves a coprecipitation combined hydrothermal process. First, the precursor is synthesized by a facile coprecipitation method. Herein, the cetyltrimethylammonium bromide (CTAB) has an important function in controlling the morphology of the precursor. With a higher degree of OH− anions and the hydrothermal process, we presume that the LiNi1/3Co1/3Mn1/3O2 nanosheets were initially obtained during the reaction process, and then the well-defined nanosheets could be formed by extension of the reaction time. At

image in Figure 5c shows that the as-synthesized NCM contains uniform nanosheets with lateral sizes of about 0.2−1 μm. As the reaction proceeds, the proportion of nanosheet structures is increased. If the reaction time is prolonged to 9 h (Figure 5d), the growth process becomes more dramatic, so that the morphology of the samples shows uniform nanosheet structures. On the basis of the above results, it is necessary to understand the formation mechanism of the LiNi1/3Co1/3Mn1/3O2 nanosheets shown in Figure S2. We propose that the formation of the 39563


Research Article


Figure 4. SEM images of the products for different hydrothermal temperatures: (a) NCM-120, (b) NCM-140, and (c) NCM-160; (d) XRD patterns of the products created at different hydrothermal temperatures: NCM-120, NCM-140, and NCM-160.

fast lithium-ion diffusion. Downsizing the nanoscale active materials has the advantages of shorter Li+ diffusion distances, larger active surface area, and stable structure.37 As illustrated in Figure S2, much more exposed interfaces of the nanosheets can greatly increase the lithium-ion diffusion and electronic conduction, thus leading to better rate stability.38 More convincing evidence for the enlarged interfaces was produced when the samples were characterized by nitrogen adsorption/ desorption analysis. The specific surface area of LiNi1/3Co1/3Mn1/3O2 (obtained at 140, 160, and 180 °C) based on the Brunauer−Emmett−Teller (BET) model was 64.2, 95.6, and 121.9 m2·g−1, respectively (Figure S3). The large surface area of the NCM-180 was due in large part to the big size particle size, which led to an increased contact area at the electrode/ electrolyte interface, promoting the transfer of ions and electrons, and most likely, higher initial capacity and stable cyclability.39 Figure 6e presents the cyclic voltammetry (CV) curves of the NCM-180 samples. The CV curves were collected in the potential range of 2.5−4.5 V at a sweep rate of 0.3 mV s−1. Redox peaks in the potential range of 3.6−3.9 V were found in both electrodes, which correspond well with the features of the cyclic voltammetry tests reported in the literature.40 The main peaks are consistent with the redox couples of Ni2+ and Co3+,

the initial stage of the reaction, the nanosheet structures appear, but they are not yet fully formed. As the reaction continues, the nanosheets are obtained in large quantities. The growth mechanism is similar to that in a report by Qian’s group.25 The electrochemical performances of the three samples (hydrothermal synthesis temperatures at 140−180 °C) were evaluated in coin-type cells, respectively. The cycling performance of the NCM-140, NCM-160, and NCM-180 electrodes for 100 cycles at 0.2 C in the range from 2.5 to 4.5 V (vs Li/Li+) is shown in Figure 6. It can be seen that the NCM-140 and NCM160 electrodes delivered a first discharge capacity of 176.4 and 189.7 mAh g−1, respectively. At the 100th cycle, the cells delivered approximately 90.7 and 92.1% of their initial discharge capacity, whereas the NCM-180 electrode (prepared at higher temperature) exhibited an initial discharge capacity of 193.6 mAh g−1. Moreover, after 100 cycles, the NCM-180 electrode still showed a very stable capacity delivery (189 mAh g−1) with a capacity retention of 97.5% (compared with the first discharge capacity). From Figure 6, the irregular morphology and low surface area of LiNi1/3Co1/3Mn1/3O2 obtained at 140 °C might be responsible for its poorer cycling stability. As is well known, nanostructured electrode materials can offer excellent chemical and physical properties, and they have promising applications in energy storage owing to their large surface-to-volume ratio and 39564


Research Article


Figure 5. SEM images of the products created after different hydrothermal reaction times at 180 °C: (a) 1 h, (b) 3 h, (c) 6 h, and (d) 9 h.

respectively, and there is no peak of Mn3+ at around 3.0 V, which makes it manifest that Mn3+ ions were not present, whereas manganese with the oxidation state of 4+ is inactive. This is believed to be beneficial for the stability of the structure. In addition to the first cycle, the following cycles overlap well, indicating the good reversibility of lithium-ion intercalation/ deintercalation in the NCM-180. Because NCM-180 is a cathode material, we wish to know its cycling performance at different discharge rates from 2.5 to 4.5 V. The discharge capacities for the NCM-180 electrode at different C-rates from 0.2 C (1 C = 220 mA g−1) to 7 C are presented in Figure 6f. The discharge capacities are obtained as 191.5, 180.4, 157.7, 132.9, 111.3, and 70.7 mA g−1, respectively, for discharge rates of 0.2, 0.5, 1, 2, 5, and 7 C, respectively. With increased discharge rates, the discharge capacities decrease regularly. When the rate was returned to 0.2 C, the cells delivered approximately 98.3% (188.4 mAh g−1) of their initial discharge capacity. Furthermore, the cycling performance of the NCM-180 nanosheet electrode at the rate of 1 C is shown in Figure 7. The initial capacities are 167.6 and 161.8 mAh g−1, respectively. It is demonstrated that there is a discharge capacity of 149 mAh g−1 even after 1000 cycles, corresponding to 92.1% of the initial capacity. A Coulombic efficiency of 96% can be obtained throughout the overall process. These results show that the

NCM-180 nanosheet electrode offers a stable long-term cycling and a very good rate capability, which should be attributed to the nanosheet structure (short Li+ transport distances and plentiful contact area with the electrolyte).41 For a better understanding of the superior electrochemical performance of the LiNi1/3Co1/3Mn1/3O2 nanosheets for lithium energy storage, the charge-transfer resistance was revealed by electrochemical impedance spectroscopy (EIS) over the frequency domain from 0.01 Hz to 100 kHz (Figure 8). Each Nyquist plot consists of a semicircle in the high-frequency range and a steeper line in the low-frequency range. The results show that the NCM-180 electrode features even steeper lines and smaller semicircles than NCM-140 and NCM-160 electrodes, and the charge transfer resistance for NCM-180 was 107 Ω, whereas that for NCM-140 and NCM-160 was 224 and 149 Ω, respectively. This suggests that the NCM-180 electrode shows a better conductivity than the NCM-140 and NCM-160, so the NCM-180 electrode could accommodate a high current density during the charge/discharge cycling and offer increased cycling stability.

■

CONCLUSIONS In summary, we have fabricated self-assembled LiNi1/3Co1/3Mn1/3O2 nanosheets via a facile synthesis method 39565


Research Article


Figure 6. Discharge−charge curves for selected cycles of (a) NCM-140, (b) NCM-160, and (c) NCM-180; cycling performance (d) of NCM-140, NCM-160, and NCM-180 at the current density of 0.2 C; cyclic voltammograms (e) for the first five cycles of NCM-180 electrode at the rate of 0.3 mV s−1; (f) charge−discharge rate performance of NCM-180 electrode at different current densities. All of the measurements are in the voltage window of 2.5−4.5 V (vs Li/Li+).

mAh g−1 at 1 C (after 1000 cycles). The LiNi1/3Co1/3Mn1/3O2 nanosheets feature efficient contact with the electrolyte and short Li+ diffusion paths, as well as sufficient void space to accommodate large volume variation. The nanosheets are very beneficial for the diffusion of Li + and high electronic conductivity. The enhanced electrical conductance and excellent

combining coprecipitation with the hydrothermal method. The test results showed that there was a very obvious influence of the reaction time and temperature on the electrochemical properties of the samples. As a cathode material, the as-synthesized LiNi1/3Co1/3Mn1/3O2 nanosheets demonstrated an outstanding electrochemical performance. The discharge capacity was 155 39566



Research Article

■

ACKNOWLEDGMENTS Financial support provided by both the National Natural Science Foundation of China (No. 21476063) and Key Projects of the Guizhou Province Department of Education (No. KY2013176) is gratefully acknowledged.

■

(1) Dunn, B.; Kamath, H.; Tarascon, J. M. Electrical energy storage for the grid: A battery of choices. Science 2011, 334, 928−935. (2) Goodenough, J. B.; Park, K. S. The Li-ion rechargeable battery: a perspective. J. Am. Chem. Soc. 2013, 135, 1167−1176. (3) Zhang, Q. F.; Uchaker, E.; Candelaria, S. L.; Cao, G. Z. Nanomaterials for energy conversion and storage. Chem. Soc. Rev. 2013, 42, 3127−3171. (4) Bruce, P. G.; Scrosati, B.; Tarascon, J. M. Nanomaterials for rechargeable lithium batteries. Angew. Chem., Int. Ed. 2008, 47, 2930− 2946. (5) Wang, K. X.; Li, X. H.; Chen, J. S. Surface and interface engineering of electrode materials for lithium-ion batteries. Adv. Mater. 2015, 27, 527−545. (6) Liu, J.; Liu, X. W. Two-Dimensional Nanoarchitectures for Lithium Storage. Adv. Mater. 2012, 24, 4097−4111. (7) Kim, T. W.; Oh, E. J.; Jee, A. Y.; Lim, S. T.; Park, D. H.; Lee, M. Y.; Hyun, S. H.; Choy, J. H.; Hwang, S. J. Soft-Chemical Exfoliation Route to Layered Cobalt Oxide Monolayers and Its Application for Film Deposition and Nanoparticle Synthesis. Chem. − Eur. J. 2009, 15, 10752−10761. (8) Goodenough, J. B.; Kim, Y. Challenges for Rechargeable Li Batteries. Chem. Mater. 2010, 22, 587−603. (9) Cheng, F.; Liang, J.; Tao, Z. L.; Chen, J. Functional materials for rechargeable batteries. Adv. Mater. 2011, 23, 1695−1715. (10) Wu, Z. C.; Li, B.; Xue, Y. J.; Li, J. J.; Zhang, Y. L.; Gao, F. Fabrication of defect-rich MoS2 ultrathin nanosheets for application in lithium-ion batteries and supercapacitors. J. Mater. Chem. A 2015, 3, 19445−19454. (11) Zhu, Y. Q.; Guo, H. Z.; Wu, Y.; Cao, C. B.; Tao, S.; Wu, Z. Y. Surface-enabled superior lithium storage of high-quality ultrathin NiO nanosheets. J. Mater. Chem. A 2014, 2, 7904−7911. (12) Zhu, Y. Q.; Cao, C. B.; Zhang, J. T.; Xu, X. Y. Two-dimensional ultrathin ZnCo2O4 nanosheets: General formation and lithium storage application. J. Mater. Chem. A 2015, 3, 9556−9564. (13) Jin, S.; Yang, G. Z.; Song, H. W.; Cui, H.; Wang, C. X. Ultrathin Hexagonal 2D Co2GeO4 Nanosheets: Excellent Li-Storage Performance and Ex-Situ Investigation of Electrochemical Mechanism. ACS Appl. Mater. Interfaces 2015, 7, 24932−24943. (14) Ge, H.; Chen, L.; Yuan, W.; Zhang, Y.; Fan, Q. Z.; Osgood, H.; Matera, D.; Song, X. M.; Wu, G. Unique mesoporous spinel Li4Ti5O12 nanosheets as anode materials for lithium-ion batteries. J. Power Sources 2015, 297, 436−441. (15) Ni, J. F.; Zhao, Y.; Li, L.; Mai, L. Q. Ultrathin MoO2 nanosheets for superior lithium storage. Nano Energy 2015, 11, 129−135. (16) Chen, C. J.; Hu, X. L.; Wang, Z. H.; Xiong, X. Q.; Hu, P.; Liu, Y.; Huang, Y. H. Controllable growth of TiO2-B nanosheet arrays on carbon nanotubes as a high-rate anode material for lithium-ion batteries. Carbon 2014, 69, 302−310. (17) Tian, X. C.; Xua, X.; He, L.; Wei, Q. L.; Yan, M. Y.; Xu, L.; Zhao, Y. L.; Yang, C. C.; Mai, L. Q. Ultrathin pre-lithiated V6O13 nanosheet cathodes with enhanced electrical transport and cyclability. J. Power Sources 2014, 255, 235−241. (18) Mei, T.; Tang, K. B.; Zhu, Y. C.; Qian, Y. T. Preparation of LiCoO2 concaved cuboctahedra and their electrochemical behavior in lithium-ion battery. Dalton Trans. 2011, 40, 7645−7650. (19) Doğangün, M.; Hang, M. N.; Troiano, J. M.; McGeachy, A. C.; Melby, E. S.; Pedersen, J. A.; Hamers, R. J.; Geiger, F. M. Alteration of Membrane Compositional Asymmetry by LiCoO2 Nanosheets. ACS Nano 2015, 9, 8755−8765. (20) Zhu, J. B.; Li, Q. Y.; Bi, W. T.; Bai, L. F.; Zhang, X. D.; Zhou, J. F.; Xie, Y. Ultra-rapid microwave-assisted synthesis of layered ultrathin

Figure 7. Cycling performance of NCM-180 electrode at current density of 1 C.

Figure 8. Electrochemical impedance spectra (EIS) of the NCM-140, NCM-160, and NCM-180 electrodes. The inset is an enlargement of the high-frequency range.

capacity demonstrate that the LiNi1/3Co1/3Mn1/3O2 nanosheets have a great potential for lithium-ion battery application.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.7b10264. Characterization, electrochemical measurements, ICPAES spectrum, EDS spectrum, and BET profiles; schematic illustration of the synthetic route, and lithiation−delithiation processes (PDF)

■

REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Zaiping Guo: 0000-0003-3464-5301 Chuanqi Feng: 0000-0002-5292-9319 Notes

The authors declare no competing financial interest. 39567


Research Article

ACS Applied Materials & Interfaces birnessite K0.17MnO2 nanosheets for efficient energy storage. J. Mater. Chem. A 2013, 1, 8154−8159. (21) Cheng, J. L.; Wang, B.; Xin, H. L.; Yang, G. C.; Cai, H. Q.; Nie, F. D.; Huang, H. Self-assembled V2O5 nanosheets/reduced graphene oxide hierarchical nanocomposite as a high-performance cathode material for lithium ion batteries. J. Mater. Chem. A 2013, 1, 10814−10820. (22) Song, H. Q.; Zhang, C. P.; Liu, Y. G.; Liu, C. F.; Nan, X. H.; Cao, G. Z. Facile synthesis of mesoporous V2O5 nanosheets with superior rate capability and excellent cycling stability for lithium ion batteries. J. Power Sources 2015, 294, 1−7. (23) Guo, S. H.; Yu, H. J.; Liu, P.; Liu, X. Z.; Li, D.; Chen, M. W.; Ishida, M.; Zhou, H. S. Surface coating of lithium−manganese-rich layered oxides with delaminated MnO2 nanosheets as cathode materials for Li-ion batteries. J. Mater. Chem. A 2014, 2, 4422−4428. (24) Zheng, J. C.; Han, Y. D.; Zhang, B.; Shen, C.; Ming, L.; Zhang, J. F. Comparative investigation of microporous and nanosheet LiVOPO4 as cathode materials for lithium-ion batteries. RSC Adv. 2014, 4, 41076− 41080. (25) Feng, Y. Y.; Zhang, H. J.; Fang, L.; Ouyang, Y.; Wang, Y. Designed synthesis of a unique single-crystal Fe-doped LiNiPO4 nanomesh as an enhanced cathode for lithium ion batteries. J. Mater. Chem. A 2015, 3, 15969−15976. (26) Sun, W. W.; Cao, F.; Liu, Y. M.; Zhao, X. Z.; Liu, X. G.; Yuan, J. K. Nanoporous LiMn2O4 nanosheets with exposed {111} facets as cathodes for highly reversible lithium-ion batteries. J. Mater. Chem. 2012, 22, 20952−20957. (27) Wang, Y. L.; Xu, X. Y.; Cao, C. B.; Shi, C.; Mo, W.; Zhu, H. S. Synthesis and performance of Li1.5V3O8 nanosheets as a cathode material for high-rate lithium-ion batteries. J. Power Sources 2013, 242, 230−235. (28) Rui, X.; Zhao, X. X.; Lu, Z. Y.; Tan, H. T.; Sim, D. H.; Hng, H. H.; Yazami, R.; Lim, T. M.; Yan, Q. Y. Olivine-type nanosheets for lithium ion battery cathodes. ACS Nano 2013, 7, 5637−5646. (29) Garcia, J. C.; Bareno, J. G.; Yan, J. H.; Chen, G. Y.; Hauser, A.; Croy, J. R.; Iddir, H. Surface Structure, Morphology, and Stability of LiNi1/3Co1/3Mn1/3O2 Cathode Material. J. Phys. Chem. C 2017, 121, 8290−8299. (30) Peng, L. L.; Zhu, Y.; Khakoo, U.; Chen, D. H.; Yu, G. H. Selfassembled LiNi1/3Co1/3Mn1/3O2 nanosheet cathodes with tunable rate capability. Nano Energy 2015, 17, 36−42. (31) Fu, F.; Xu, G. L.; Wang, Q.; Deng, Y. P.; Li, X.; Li, J. T.; Huang, L.; Sun, S. G. Synthesis of single crystalline hexagonal nanobricks of LiNi1/3Co1/3Mn1/3O2 with high percentage of exposed {010} active facets as high rate performance cathode material for lithium-ion battery. J. Mater. Chem. A 2013, 1, 3860−3864. (32) Hua, W. B.; Guo, X. D.; Zheng, Z.; Wang, Y. J.; Zhong, B. H.; Fang, B. Z.; Wang, J. Z.; Chou, S. L.; Liu, H. Uncovering a facile largescale synthesis of LiNi1/3Co1/3Mn1/3O2 nanoflowers for high power lithium-ion batteries. J. Power Sources 2015, 275, 200−206. (33) Li, J. L.; Wang, X. F.; Zhao, J. W.; Chen, J.; Jia, T. K.; Cao, C. B. Porous lithium nickel cobalt manganese oxide hierarchical nanosheets as high rate capability cathodes for lithium ion batteries. J. Power Sources 2016, 307, 731−737. (34) Pi, W. B.; Mei, T.; Zhang, Z. X.; Li, X.; Wang, J. Y.; Li, J. H.; Wang, X. B. Synthesis of disk-like LiNi1/3Co1/3Mn1/3O2 nanoplates with exposed (001) planes and their enhanced rate performance in a lithium ion battery. CrystEngComm 2017, 19, 442−446. (35) Hashem, A. M. A.; Abdel-Ghany, A. E.; Eid, A. E.; Trottier, J.; Zaghib, K.; Mauger, A.; Julien, C. M. Study of the surface modification of LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion battery. J. Power Sources 2011, 196, 8632−8637. (36) Marcinek, M. L.; Wilcox, J. W.; Doeff, M. M.; Kostecki, R. M. Microwave Plasma Chemical Vapor Deposition of Carbon Coatings on LiNi1/3Co1/3Mn1/3O2 for Li-Ion Battery Composite Cathodes. J. Electrochem. Soc. 2009, 156, A48−A51. (37) Wang, F. X.; Xiao, S. Y.; Chang, Z.; Yang, Y. Q.; Wu, Y. P. Aqueous Rechargeable Battery Based on Zinc and a Composite of LiNi1/3Co1/3Mn1/3O2. Chem. Commun. 2013, 49, 9209−9211.

(38) Zhang, X. D.; Bi, Z. Y.; He, W.; Yang, G.; Liu, H.; Yue, Y. Z. Fabricating high-energy quantum dots in ultra-thin LiFePO4 nanosheets using a multifunctional high-energy biomolecule−ATP. Energy Environ. Sci. 2014, 7, 2285−2294. (39) Zhao, Y.; Peng, L. L.; Liu, B.; Yu, G. H. Single-crystalline LiFePO4 nanosheets for high-rate Li-ion batteries. Nano Lett. 2014, 14, 2849− 2853. (40) Yang, C.; Zhang, X. S.; Huang, M. Y.; Huang, J. J.; Fang, Z. B. Preparation and Rate Capability of Carbon Coated LiNi1/3Co1/3Mn1/3O2 as Cathode Material in Lithium Ion Batteries. ACS Appl. Mater. Interfaces 2017, 9, 12408−12415. (41) Cheng, Q.; Yang, T.; Li, M.; Chan, C. K. Exfoliation of LiNi1/3Co1/3Mn1/3O2 into Nanosheets using Electrochemical Oxidation and Reassembly with Dialysis or Flocculation. Langmuir 2017, 33, 9271.

39568


3O2 Nanosheet Cathode with High

Recommend Documents