Research Article www.acsami.org
Synthesis of MXene/Ag Composites for Extraordinary Long Cycle Lifetime Lithium Storage at High Rates Guodong Zou,† Zhiwei Zhang,† Jianxin Guo,† Baozhong Liu,†,‡ Qingrui Zhang,*,§ Carlos Fernandez,¶ and Qiuming Peng*,† †
State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, P.R. China School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, P.R. China § Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, P.R. China ¶ School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen AB107GJ, United Kingdom ‡
S Supporting Information *
ABSTRACT: A new MXene/Ag composite was synthesized by direct reduction of a AgNO3 aqueous solution in the presence of MXene (Ti3C2(OH)0.8F1.2). The as-received MXene/Ag composite can be deemed as an excellent anode material for lithium-ion batteries, exhibiting an extraordinary long cycle lifetime with a large capacity at high charge−discharge rates. The results show that Ag self-reduction in MXene solution is related to the existence of lowvalence Ti. Reversible capacities of 310 mAh·g−1 at 1 C (theoretical value being ∼320 mAh·g−1), 260 mAh·g−1 at 10 C, and 150 mAh· g−1 at 50 C were achieved. Remarkably, the composite withstands more than 5000 cycles without capacity decay at 1−50 C. The main reasons for the long cycle life with high capacity are relevant to the reduced interface resistance and the occurrence of Ti(II) to Ti(III) during the cycle process. KEYWORDS: MXene, self-reduction, lithium batteries, composite layer is 320 mAh·g−1,10 it decreases to 67 and 130 mAh·g−1 for Ti3C2(OH)2 and Ti3C2F2 semiconductors, respectively.11,12 Therefore, significant effort has been put into improving the gravimetric capacity of the Ti3C2 conductor by modifying the surface termination/state of MXene or by forming MXenebased composites with other high lithium storage capacity materials. For example, the capacity and cyclability of MXene composites can be significantly improved by adding other materials with large capacities and high conductivity such as carbon additives,5 carbon-nanotube doping,13 and Sn4+ ion intercalation.14 However, owing to the volume swelling and weak conductivity, long cycle time and high-rate capacity in MXene materials have not been achieved. Notably, the exterior groups of MXene, which were prepared by removing the Al layer from Ti3AlC2 in HF solution, not only provide direct ion exchange sites15 but also act as an effective reductant to some oxides such as Mn(VII), Cr(VI), and Fe(III).16 This special reductive role offers a prerequisite to tailor the chemical properties of MXene. Namely, some new MXene-metal composites are expected to be synthesized in a
1. INTRODUCTION The performance of anode materials plays a crucial role in lithium-ion batteries (LIBs);1 thus, extensive research efforts have been devoted to exploring new anode materials with better performance. Although Sn and Si possess very high specific capacities, both of them experience large volume changes during the cycle process, which causes powdering of active materials and results in a sharp decrease in capacity.2,3 Therefore, developing new electrode materials with high capacities at long cycles remains a challenge in LIBs. Two-dimensional (2D) materials such as graphene,4 carbides,5 nitrides,6 oxides, and chalcogenides7 have recently attracted broad interest because of their unique structural and chemical properties, which make them promising electrode materials for new-generation LIBs. Among these 2D materials, the group of transition-metal carbides labeled as MXene (Ti3C2(OHxF1−x)2), recently reported by Gogotsi and Barsoum et. al.,8,9 are potential electrode materials for LIBs because of their layered structure similar to that of graphite, providing effective lithium storage space. However, the metallic Ti3AlC2 precursor is prone to form Ti 3 C 2 (OH) 2 and Ti 3 C 2 F 2 semiconductors when its surface is terminated with OH and F groups, respectively. Therefore, though the theoretical specific capacity of the metallic Ti3C2 conductor with one Li © 2016 American Chemical Society
Received: July 5, 2016 Accepted: August 11, 2016 Published: August 12, 2016 22280
DOI: 10.1021/acsami.6b08089 ACS Appl. Mater. Interfaces 2016, 8, 22280−22286
Research Article
ACS Applied Materials & Interfaces
Figure 1. (a) Representative SEM image of the layered MXene/10Ag sample. (b) High-magnification image of a local area in panel a. (c) XRD patterns of samples with different amounts of Ag. (d) Typical TEM image of the MXene/10Ag sample. The inset corresponds to the SAED along the [1−10] direction. (e) High-resolution TEM image of a Ag particle. (f) Particle size distribution. 2.3. Preparation of MXene/Ag Composites. MXene (100 mg) was dispersed in 80 mL of deionized water and ultrasonically treated for 30 min. After that, it was further stirred for another 10 min to obtain a uniform suspension. In addition, 50 mg of AgNO3 (99.8 wt %, Aladdin Reagent) was dissolved in 20 mL of deionized water. Taking into account its low cost and easy storage, we used AgNO3 as our silver salt instead of other silver salts. Then, the AgNO3 aqueous solution was slowly injected into the uniform suspension. After reacting for 10 min, the MXene/10Ag suspension was centrifuged and rinsed three times using absolute ethyl alcohol. Finally, the MXene/ 10Ag composite was dried in vacuum at 80 °C for 24 h. For comparison, MXene/5Ag and MXene/15Ag composites were synthesized under the same conditions as described above, except the mass of AgNO3 was changed. 2.4. Cell Measurements. Cell measurements were performed using coin-type 2016 cells with pure lithium metal as both the counter electrode and reference electrode at room temperature. The working electrodes, consisting of 80 wt % active materials (MXene or MXene/ Ag), 10 wt % acetylene black, and 10 wt % polyvinylidene fluoride (PVDF), were prepared with the aid of N-methyl-2-pyrrolidinone (NMP). The electrolyte was 1 M LiPF6 in the mixture of ethylene carbonate (EC):dimethyl carbonate (DMC):ethylmethyl carbonate (EMC) in a 1:1:1 volume ratio. The separator was a polypropylene membrane (Celgard 2400). The cells were assembled in an argon-filled glovebox with concentrations of H2O and O2 below 1.0 ppm. The galvanostatic charge−discharge measurements were carried out using a LAND-CT2001C test system at different current rates (1 C = 320 mAh·g−1) under the voltage between 0.01 and 3 V versus Li+/Li. The cyclic voltammogram (CV) was obtained using an electrochemical workstation (Biologic, VSP) at a scan rate of 0.2 mV/s from 0.01 to 3 V. Electrochemical impedance spectroscopy (EIS) was conducted on an electrochemical workstation (Biologic, VSP) in the frequency ranging from 100 to 0.01 kHz with an alternating current amplitude of 5 mV. 2.5. Analysis and Characterization. X-ray diffraction (XRD) patterns were obtained with a powder diffractometer (Rigaku D/ MAX-2005/PC) using Cu Kα radiation (λ = 1.5406 Å) at a voltage of 40 kV and a current of 200 mA with a step scan of 0.02° per step and a scanning speed of 2°/min. A typical scanning electron microscope (SEM, Hitachi S4800, Japan) was used to observe the microstructures of the samples. Transmission electron microscopy (TEM) characterizations were conducted on a JEOL JEM2010 transmission electron microscope
way in which the surfaces are covered by metal nanoparticles. These materials have at least two-fold merits. The layered body structure improves chemical properties of nanosized particles by inhibiting aggregation and increasing electron transfer efficiency. Conversely, the formation of nanoscale metallic particles on the surface of MXene provides a great opportunity to improve electrical conductivity of MXene, increasing performance in both batteries and supercapacitors. Herein, we report the synthesis of a new MXene/Ag composite comprised of layered MXene templates and nanosized Ag particles by direct reduction of a AgNO3 aqueous solution in the presence of MXene. The layered MXene acts as both a supporter and a reductant during the reaction process. Attributed to the improved electronic conductivity and the formation of Ti(III), this new MXene/Ag composite shows a large capability at high charge−discharge rates and an outstanding long cycle life when being used as an anode material for LIBs.
2. EXPERIMENTAL SECTION 2.1. Preparation of MAX (Ti3AlC2). The powder mixtures of Ti (99.5% purity, 325 mesh, Aladdin Reagent), C (99.5% purity, 2−4 μm, Aladdin Reagent), and Al (99.95% purity, 200 mesh, Aladdin Reagent) in a 1:1:1.8 molar ratio were sealed in a steel jar under an argon protective atmosphere. Then, the mixtures were milled at 300 rpm for 4 h. After being milled, the mixtures were filled into a graphite die with a diameter of 20.5 mm and sintered by a spark plasma sintering device (SPS 3.20MK-IV, Sumitomo Coal Mining Co., Ltd., Japan) at 1350− 1400 °C under a pressure of 30 MPa. The soaking time was 10 min, and the heating rate was 80 °C/min. After being sintered, the surfaces of the samples were ground with SiC to remove the graphite layer. Finally, the Ti3AlC2 bulk was milled at 400 rpm for 6 h to obtain the Ti3AlC2 powder. 2.2. Preparation of MXene. MXene was prepared through a conventional method. Briefly, MXene was synthesized by selectively etching the aluminum layer out of the prepared Ti3AlC2 powder in 40% HF (Aladdin Reagent) for 10 h at room temperature. After HF treatment, the solution was centrifuged and rinsed three times using deionized water until the pH of the solution reached ∼5. Then, the sample was dried in vacuum at 80 °C for 24 h. 22281
DOI: 10.1021/acsami.6b08089 ACS Appl. Mater. Interfaces 2016, 8, 22280−22286
Research Article
ACS Applied Materials & Interfaces equipped with a Gatan CCD camera working at an accelerating voltage of 200 kV. Elemental compositions were detected by an energy dispersive X-ray (EDX) analyzer with an AMETEK/EDAX Genesis attachment (EDAX Inc., Mahwah, NJ, United States) mounted on the TEM. Nine random spots were performed to calculate the elemental composition. All TEM samples were made by depositing a drop of diluted suspension in ethanol on a carbon film-coated copper grid. The elemental contents (Ti and Ag) of the MXene/Ag composites were measured using inductively coupled plasma (ICP) (ICAP 6300 Thermo Scientific, United States). XPS analysis of given samples was performed with a spectrometer (ESCALAB-2, U.K.) equipped with a Mg Kα X-ray source (1253.6 eV proton).
account the low theoretical specific capacity of OH groups, we used the as-obtained MXene powder (Ti3C2(OH)0.8F1.2)17 for Ag reduction directly. The SEM image (Figure 1a) reveals that the layered structure of MXene remains. In addition, some particles were observed on the surfaces of MXene (Figure 1b). From the XRD pattern (Figure 1c), there are four major diffraction peaks which can be indexed to the (111), (200), (220), and (311) planes of the face-centered-cubic Ag single crystal. The calculated lattice constant is 4.01 Å, which is close to the reported value.18 With increasing Ag concentration, the Ag peaks become sharper and the intensities increase, indicating that the crystallinity of Ag is improved. In addition, the (002) peak intensity of MXene at ∼9° becomes weak, suggesting less order along c direction. The (002) peak position of MXene remains unchanged, implying that no Ag intercalation occurs. The TEM images (Figure 1d and e) reveal that the Ag particles mainly distribute on the surfaces of MXene/10Ag (containing ∼10 wt % Ag, Table 1). Ag nanoparticles are single crystalline, as evidenced by the sharp selected area electron diffraction pattern (SAED) of a nanoparticle along the [1−10] zone axis. Examination of an individual nanoparticle with highresolution TEM shows that it is a single crystal. The average particle size of Ag is ∼35.2 ± 5 nm (Figure 1f). Lattice figures with an interplanar spacing of d111 = 0.238 ± 0.02 nm are clearly visible. As the concentration of AgNO3 increases, both the size and amount of Ag particles increase correspondingly, according to TEM observations as well as the average size calculated by the Scherrer formula (Figure S1 and Table 1). They show the similar trends except that the particle size calculated by the Scherrer formula is smaller than that measured by TEM observation. The reason for the discrepancy is that XRD patterns reflect an average bulk value, while TEM results generally reflect a local area. With increasing Ag concentration from 5 to 15%, the size of Ag particles increases from ∼10 nm to more than 100 nm, respectively.
3. RESULTS AND DISCUSSION A typical exfoliation process of layered Ti3AlC2 powders was performed by immersing them in 40% HF solution at room Table 1. Average Ag Particle Sizes Determined by Both XRD and TEMa average Ag sizes (nm)
elemental compositions (mg/L)
sample
XRD
TEM
Ti
Ag
Ag concentration (wt %)
MXene/5Ag MXene/10Ag MXene/15Ag
9 28 157
11 34 180
23.4 13.2 8.5
1.6 2.0 2.1
4.5 10.2 15.6
In the XRD method, we used the Scherrer formula D = kλ/β cos θ, where k = 0.9, λ = 0.154 nm, β = the broadening peak width at the half peak height in radians, and θ = Bragg angle to calculate the grain size. In the TEM method, the particle size was obtained by taking the average value of 20 particles). The elemental compositions were confirmed by ICP testing. a
temperature.17 The average particle size of the starting Ti3AlC2 is ∼3 μm. After being immersed in 40% HF solution at room temperature for 10 h, open arch-shaped edges at the ends of the MXene layers resembling graphene were observed. Taking into
Figure 2. (a) XPS profiles of the MXene and MXene/10Ag samples. (b) Ti 2p3/2 in the MXene. (c) Ti 2p3/2 in the MXene/10Ag. (d) Ag 3d3/2 in the MXene/10Ag. 22282
DOI: 10.1021/acsami.6b08089 ACS Appl. Mater. Interfaces 2016, 8, 22280−22286
Research Article
ACS Applied Materials & Interfaces
Figure 3. Cyclic voltammetry curves of the MXene (a) and MXene/10Ag (b) samples at the initial 5 cycles. (c) Charge−discharge curves of the MXene/10Ag sample at 1 C. (d) Comparative reversible delithiation capacity of the MXene and MXene/10Ag samples for 3000−5000 cycles. Coulombic efficiency is plotted for the MXene/10Ag only. (e) Rate capabilities of the MXene and MXene/10Ag samples at different current rates from 1 to 50 C. Coulombic efficiency is plotted for the MXene/10Ag sample with 1C only.
neously, the representative Ag 3d5/2 and Ag 3d3/2 peaks (Figure 2d) are located at ∼367.8 and ∼373.8 eV with the slitting of the 3d doublet of ∼6.0 eV, suggesting the successful reduction for Ag(0) formation. Additionally, considering the possible presence of different Ag species, the Ag 3d peaks have been fitted using the software XPS peak fit after a Shirley background subtraction. Amazingly, nearly all silvers are in the Ag(0) (metallic) state and the Ag+ and Ag2+ species are negligible, which further proves the strong reductive activity on the lowvalence Ti(II) and Ti(III) species. Therefore, Ag self-reduction is ascribed to the activated low-valence Ti species. The electrochemical performance of the MXene and MXene/10Ag composite as anode materials for LIBs was investigated, and the typical CV curves at the initial 5 cycles are shown in Figures 3a and b. Two broad irreversible reduction peaks around 1.66 and 0.62 V were observed in the first lithiation process. It is mainly attributed to the formation of a solid electrolyte interphase in combination with the intercalation of Li+ between the sheets of MXene and MXene/Ag electrode materials.20 During the first delithiation process, two wide anodic peaks were detected at ∼1.96 and ∼2.44 V. In addition, a new peak at ∼0.37 V was detected in the MXene/ 10Ag, which is attributed to the extraction of lithium ions from the MXene/Ag electrodes.21−23 One possible reason for the presence of peak at ∼0.37 V was related to the formation of transition-state Ti during the reduction processing,14 which changes to some stable Ti compound after cycling. No significant peak shift in the subsequent cycles was found, indicating that the charge storage in both MXene and MXene/ Ag electrode materials is the intercalation of Li+ rather than a conversion reaction.21 The representative galvanostatic charge−discharge potential curves of MXene/Ag composites and MXene at a current density of 1 C (320 mA·g−1) are shown in Figures 3c and S2a−
Table 2. Summary of the Electrochemical Performance of Different MXene-Based Anode Materials at High Current Densities current density (C)
cycle number
specific capacity (mAh·g−1)
delaminated Ti3C2“paper” In−Ti3C2 exfoliated Ti2C Ti2C-based negative electrodes Nb2CTx electrodes V2CTx electrodes Ti3C2−CNF Ti3C2−CNF MXene/10Ag
36
720
110
12
10 10 10
100 100 1000
69 70 60
13 13 14
10
150
110
23
10
150
125
23
1 100 1
300 2900 5000
320 97 310
MXene/10Ag
10
5000
260
MXene/10Ag
50
5000
150
24 25 this work this work this work
component
refs
To elucidate the possible self-reduction mechanism, XPS investigation was conducted for MXene and MXene/10Ag (Figure 2a). The distinct peak at ∼458.8 eV from primitive MXene samples is assigned to Ti(IV) 2p3/2 (Figure 2b). The broad peak ranging from 453−457 eV suggests the possible presence of low-valence Ti species, i.e., Ti(II) (∼454.7 eV) and Ti(III) (∼455.8 eV)19 (Figure 2c). The self-reduction process onto MXene/Ag (10 wt %) can lead to the initial transformation from Ti(III) to the terminated Ti(IV) species with the area fractions of 16.5 and 9.6%, respectively. Simulta22283
DOI: 10.1021/acsami.6b08089 ACS Appl. Mater. Interfaces 2016, 8, 22280−22286
Research Article
ACS Applied Materials & Interfaces
Figure 4. (a) Nyquist plots of impedances for the MXene and MXene/10Ag samples after five cycles. The inset corresponds to the equivalent circuit diagram. (b) Typical TEM image of the MXene/10Ag electrode after 2000 cycles. The inset shows the particle distribution (randomly measured 50 particles). High-resolution TEM images of the MXene/10Ag electrode after 5 cycles (c) and 2000 cycles (d) at 1 C. (e) Ti 2p3/2 in the MXene/10Ag sample after 2000 cycles. (f) Ti 2d3/2 in the MXene/30Ag after 2000 cycles.
the grain size is smaller than the width of space-charge zones,23 resembling ionic charge carriers.19 Hence, the formation of Ag particles on the surface of MXene changes the electrical properties of MXene substrate, accelerating Li+ ion diffusion along MXene layers. Figure 3d shows the rate capability of the MXene and MXene/10Ag samples at different current rates. Remarkably, compared with MXene and other MXene/Ag composites (Figure S3), the MXene/10Ag reveals better cyclic capacity retention at various current rates of 1−50 C. For the MXene, it exhibits a specific charge capacity of 220.0 mAh·g−1 at 1 C, and the capacity drops quickly to 131.5, 100.7, 86.6, and 47.4 mAh· g−1 at 5, 10, 20, and 50 C, respectively. In the case of the MXene/10Ag sample, a high capacity of 150.0 mAh·g−1 remains even at 50 C. Moreover, when the current density of charge rate returns to 1 C, the MXene/10Ag electrode recovers its previous reversible capacity value, implying its excellent rate reversibility. Figure 3e compares the cycling stability of the MXene and MXene/10Ag electrodes. The MXene/10Ag shows a capacity of 310.0 mAh·g−1 at 1 C after 800 cycles, which is close to the theoretical capacity of the MXene/10Ag (320.0 mAh·g−1, the addition of Ag does not provide the capacity). A constant value of 260.0 mAh·g−1 at 10 C after 1000 cycles is also observed. More attractively, the MXene/10Ag sample is still able to provide a steady-state capacity of 150.0 mAh·g−1 at 50 C even after 5000 cycles. In contrast, the capacity of MXene decreases with increasing cycles, and it finally reaches a steady value of 34 mAh·g−1 at 10 C after 500 cycles. The capacity of 150.0 mAh·g−1 at 50 C after 5000 cycles for the MXene/10Ag is much higher than that of the broadly used graphite anode in commercial LIBs. The latter loses more than 80% of its theoretical capacity to about 75 mAh·g−1 after ∼1000 cycles at 10 C.23 It is also much higher than those of other MXene composites at high current rates reported so far (Table 2).12−14,23−25 Figure 4a compares the Nyquist plots of the MXene and MXene/Ag electrodes after five cycles. The inset is an equivalent circuit model. The depressed semicircle in the
Table 3. Fitting EIS Results of Samples at Different States samples
Rs (Ω)
error (%)
Rct (Ω)
error (%)
MXene MXene/5Ag (after 5 cycles) MXene/10Ag (after 5 cycles) MXene/15Ag (after 5 cycles) MXene/10Ag (after 100 cycles) MXene/10Ag (after 800 cycles) MXene/10Ag (after 1000 cycles) MXene/10Ag (after 2000 cycles) MXene/10Ag (after 3000 cycles)
2.773 1.806 1.237 1.534 2.123 1.569 1.413 1.353 1.291
0.8711 1.212 1.067 0.6372 1.2321 0.5126 0.8242 0.6436 0.6197
121.4 85.21 59.28 70.06 92.61 71.61 65.16 63.27 60.45
0.3626 0.4914 1.128 0.3461 0.3241 0.3461 0.6124 0.4388 0.7645
c. In the first discharge curves, the initial discharge capacities of MXene and MXene/10Ag are ∼420 and ∼550 mAh·g−1, respectively. However, their values decrease to ∼250 and ∼330 mAh·g−1 in the second cycle, respectively. In the subsequent cycles, the charge−discharge capacity of MXene decreases continuously. Nevertheless, the overlap of the charge− discharge curves after 800 cycles indicates good stability of the MXene/Ag electrodes. An obvious activation process that was observed in the initial several hundred cycles was also observed in the MXene/Ag samples (Figure 3d). Further, the capacity below 1 V is about half of the reversible capacity for the MXene sample, which is consistent with both Ti3C2 and Ti2C electrodes.11 On the other hand, the capacity fraction below 1 V is about two-thirds of that of the MXene/10Ag sample, which is similar to V2C-based MXene.22 Note that the narrow charge plateau at 0.37 V is more apparent at a low rate of 0.3 C (Figure S2d). It is believed that the formation of unstable transition-state Ti is easier to change to a stable Ti compound at high-rate charge−discharge cycles. Thus, it is hardly detected at high rates. It is interesting that the voltage of MXene/Ag dropped much more slowly than that of MXene in region A of Figure 3c. The discharge process of region A is mainly due to the homogeneous insertion of Li+ ions into the interface of the matrix, which is associated with the size effects that the potential profiles tend to become flatter initially when 22284
DOI: 10.1021/acsami.6b08089 ACS Appl. Mater. Interfaces 2016, 8, 22280−22286
Research Article
ACS Applied Materials & Interfaces high-to-medium frequency region and the inclined line in the low-frequency range correspond to the charge transfer resistance (Rct) and Warburg impedance (Ws) related to Li+ ion diffusion in the active materials, respectively.8,26 Apparently, the fitting results (Table 3) indicate that the MXene/Ag composites show lower values of charge transfer resistance than that of the MXene. With suitable Ag concentration as well as fine and homogeneous Ag nanoparticles, the smallest value of 59.28 Ω is achieved for the MXene/10Ag. Moreover, as the cycle number increases, the particle size of Ag reduces (Figure 4b), and its distribution becomes more homogeneous (Figure S4). Then, the interface fraction between MXene and Ag increases, resulting in a decrease in both Rct and Ws (Figure S5 and Table 3). Thus, the electrolyte easily penetrates the surfaces of MXene/10Ag layers and contributes to ion diffusion, accelerating the intercalation of Li+ ions. For example, the layer distance increases from 0.986 to 1.061−1.278 nm when the cycles are increased to 2000 (Figures 4c and d and S6). Therefore, as the cycles increase, the intercalation of Li+ occurs continuously, and the capacity is improved to close to its theoretical value. To further probe the presumable mechanism on activation process-increased capacity during the cycle process, the amount of variation of different valence Ti species was confirmed by XPS. Interestingly, 2000 cycles of battery circulation can result in an apparent fraction increase on Ti(III) (9.6 to 23.4%) and weakened Ti(II) species (Figure 4e), indicating possible Ti transformation from Ti(II) to Ti(III). It is well-known that Ti(III) species can provide strong conductivity, which significantly favors the excellent circulation property.27,28 Comparatively, the primitive MXene displays the negligible Ti species variations after battery circulation, further proving the important catalytic roles on Ag species (Figure S7a). In addition, the high Ag loadings (30 wt %) can lead to a complete oxidation of low-valence Ti(II) and Ti(III) species during the self-reduction process, and no obvious Ti(III) species are generated after 2000 cycles with the declining circulation property (Figures 4f and S7b). It further demonstrates that the efficient Ti (III) species originate from Ti(II) rather than Ti(IV) reduction, revealing that the high loaded amount fabrication is not always a smart choice.
■
AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS We greatly acknowledge financial support from NSFC (Grants 51422105, 51578476, and 51471065), The Science Foundation for the Excellent Youth Scholars from Universities of Hebei Province (Grant GCC2014058), NSF of Hebei Province (Grant No. B2016203056) and the Natural Science Foundation for Distinguished Young Scholars of Hebei Province of China (Grant E2015203404), Heibei Province Youth Top-Notch Talent Program. We also thank Dr. Yue Qi and Dr. Jianyu Huang for their language check and beneficial discussion.
■
REFERENCES
(1) Armand, M.; Tarascon, J. M. Building Better Batteries. Nature 2008, 451, 652−657. (2) Ji, L.; Tan, Z.; Kuykendall, T.; An, E. J.; Fu, Y.; Battaglia, V.; Zhang, Y. Multilayer Nanoassembly of Sn-Nanopillar Arrays Sandwiched between Graphene Layers for High-Capacity Lithium Storage. Energy Environ. Sci. 2011, 4, 3611−3616. (3) Yu, Y.; Gu, L.; Zhu, C.; Tsukimoto, S.; van Aken, P. A.; Maier, J. Reversible Storage of Lithium in Silver-Coated Three-Dimensional Macroporous Silicon. Adv. Mater. 2010, 22, 2247−2250. (4) Geim, A. K.; Novoselov, K. S. The Rise of Graphene. Nat. Mater. 2007, 6, 183−191. (5) Zeng, Z.; Yin, Z.; Huang, X.; Li, H.; He, Q.; Lu, G.; Boey, F.; Zhang, H. Single-Layer Semiconducting Nanosheets: High-Yield Preparation and Device Fabrication. Angew. Chem., Int. Ed. 2011, 50, 11093−11097. (6) Cao, L.; Fan, P.; Vasudev, A. P.; White, J. S.; Yu, Z.; Cai, W.; Schuller, J. A.; Fan, S.; Brongersma, M. L. Semiconductor Nanowire Optical Antenna Solar Absorbers. Nano Lett. 2010, 10, 439−445. (7) Zhou, K. G.; Mao, N. N.; Wang, H. X.; Peng, Y.; Zhang, H. L. A Mixed-Solvent Strategy for Efficient Exfoliation of Inorganic Graphene Analogues. Angew. Chem., Int. Ed. 2011, 50, 10839−10842. (8) Ghidiu, M.; Lukatskaya, M. R.; Zhao, M. Q.; Gogotsi, Y.; Barsoum, M. W. Conductive Two-Dimensional Titanium Carbide /Clay/ with High Volumetric Capacitance. Nature 2014, 516, 78−81. (9) Lukatskaya, M. R.; Mashtalir, O.; Ren, C. E.; Dall’Agnese, Y.; Rozier, P.; Taberna, P. L.; Naguib, M.; Simon, P.; Barsoum, M. W.; Gogotsi, Y. Cation Intercalation and High Volumetric Capacitance of Two-Dimensional Titanium Carbide. Science 2013, 341, 1502−1505. (10) Tang, Q.; Zhou, Z.; Shen, P. Are MXenes Promising Anode Materials for Li Ion Batteries? Computational Studies on Electronic Properties and Li Storage Capability of Ti3C2 and Ti3C2X2 (X= F, OH). J. Am. Chem. Soc. 2012, 134, 16909−16916. (11) Naguib, M.; Come, J.; Dyatkin, B.; Presser, V.; Taberna, P. L.; Simon, P.; Barsoum, M. W.; Gogotsi, Y. MXene: a Promising Transition Metal Carbide Anode for Lithium-Ion Batteries. Electrochem. Commun. 2012, 16, 61−64. (12) Andrey, N. E.; Alexander, L. I. Structural and Electronic Properties and Stability of MXenes Ti2C and Ti3C2 Functionalized by Methoxy Groups. J. Phys. Chem. C 2013, 117, 13637−13643. (13) Yan, P.; Zhang, R.; Jia, J.; Wu, C.; Zhou, A.; Xu, J.; Zhang, X. Enhanced Supercapacitive Performance of Delaminated Two-Dimensional Titanium Carbide/Carbon Nanotube Composites in Alkaline Wlectrolyte. J. Power Sources 2015, 284, 38−43.
4. CONCLUSIONS In summary, this investigation offers a new method to fabricate some novel MXene-metal composites with unique chemical properties by means of direct reduction role of as-obtained MXene materials. Taking Ag metal as an example, we prepared a new MXene/Ag composite by directly reducing a AgNO3 aqueous solution with the addition of the as-obtained MXene (Ti3C2(OH)0.8F1.2). The new MXene/10Ag composite is deemed as a potential electrode material for Li-ion batteries in terms of superior rate capability and excellent long-term cyclability. It withstands more than 5000 cycles without capacity decay at 1−50 C. We foresee an enormous potential impact of this methodology in exploiting new physical and chemical properties of different MXene-metal composites.
■
SEM and TEM images, charge−discharge curves, cycling performance graphs, EDS elemental distribution maps, EIS curves, XRD patterns, and XPS profiles (PDF)
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.6b08089. 22285
DOI: 10.1021/acsami.6b08089 ACS Appl. Mater. Interfaces 2016, 8, 22280−22286
Research Article
ACS Applied Materials & Interfaces (14) Luo, J.; Tao, X.; Zhang, J.; Xia, Y.; Huang, H.; Zhang, L.; Gan, Y.; Liang, C.; Zhang, W. Sn4+ Ion Decorated Highly Conductive Ti3C2 MXene: Promising Lithium-Ion Anodes with Enhanced Volumetric Capacity and Cyclic Performance. ACS Nano 2016, 10, 2491−2499. (15) Peng, Q.; Guo, J.; Zhang, Q.; Xiang, J.; Liu, B.; Zhou, A.; Liu, R.; Tian, Y. Unique Lead Adsorption Behavior of Activated Hydroxyl Group in Two-Dimensional Titanium Carbide. J. Am. Chem. Soc. 2014, 136, 4113−4116. (16) Ying, Y.; Liu, Y.; Wang, X.; Mao, Y.; Cao, W.; Hu, P.; Peng, X. Two-Dimensional Titanium Carbide for Efficiently Reductive Removal of Highly Toxic Chromium(VI) from Water. ACS Appl. Mater. Interfaces 2015, 7, 1795−1803. (17) Zou, G.; Guo, J.; Peng, Q.; Zhou, A.; Zhang, Q.; Liu, B. Synthesis of Urchin-Like Rutile Titania Carbon Nanocomposites by Iron-Facilitated Phase Transformation of MXene for Environmental Remediation. J. Mater. Chem. A 2016, 4, 489−499. (18) Sun, X. M.; Li, Y. D. Cylindrical Silver Nanowires: Preparation, Structure, and Optical Properties. Adv. Mater. 2005, 17, 2626−2630. (19) Chen, J. S.; Liu, H.; Qiao, S. Z.; Lou, X. W. Carbon-Supported Ultra-Thin Anatase TiO2 Nanosheets for Fast Reversible Lithium Storage. J. Mater. Chem. 2011, 21, 5687−5692. (20) Ni, K.; Chen, L.; Lu, G. Synthesis of Silver Nanowires with Different Aspect Ratios as Alcohol-Tolerant Catalysts for Oxygen Electroreduction. Electrochem. Commun. 2008, 10, 1027−1030. (21) Yao, H.; Zheng, G.; Li, W.; McDowell, M. T.; Seh, Z.; Liu, N.; Lu, Z.; Cui, Y. Crab Shells as Sustainable Templates from Nature for Nanostructured Battery Electrodes. Nano Lett. 2013, 13, 3385−3390. (22) Liu, Y.; Wang, W.; Ying, Y.; Wang, Y.; Peng, X. Binder-Free Layered Ti3C2/CNTs Nanocomposite Anodes with Enhanced Capacity and Long-Cycle Life for Lithium-Ion Batteries. Dalton Trans. 2015, 44, 7123−7126. (23) Naguib, M.; Halim, J.; Lu, J.; Cook, K. M.; Hultman, L.; Gogotsi, Y.; Barsoum, M. W. New Two-Dimensional Niobium and Vanadium Carbides as Promising Materials for Li-Ion Batteries. J. Am. Chem. Soc. 2013, 135, 15966−15970. (24) Come, J.; Naguib, M.; Rozier, P.; Barsoum, M. W.; Gogotsi, Y.; Taberna, P. L. A Non-Aqueous Asymmetric Cell with a Ti2C-based Two-Dimensional Negative Electrode. J. Electrochem. Soc. 2012, 159, A1368−A1372. (25) Lin, Z.; Sun, D.; Huang, Q.; Yang, J.; Barsoum, M. W.; Yan, X. Carbon Nanofiber Bridged Two-Dimensional Titanium Carbide as a Superior Anode for Lithium-Ion Batteries. J. Mater. Chem. A 2015, 3, 14096−14102. (26) Mashtalir, O.; Naguib, M.; Mochalin, V. N.; Dall’Agnese, Y.; Heon, M.; Barsoum, M. W. Intercalation and Delamination of Layered Carbides and Carbonitrides. Nat. Commun. 2013, 4, 1716−1722. (27) Sivakkumar, S. R.; Nerkar, J. Y.; Pandolfo, A. G. Rate Capability of Graphite Materials as Negative Electrodes in Lithium-Ion Capacitors. Electrochim. Acta 2010, 55, 3330−3335. (28) Chen, X.; Liu, L.; Yu, P. Y.; Mao, S. S. Increasing Solar Absorption for Photocatalysis with Black Hydrogenated Titanium Dioxide Nanocrystals. Science 2011, 331, 746−750.
22286
DOI: 10.1021/acsami.6b08089 ACS Appl. Mater. Interfaces 2016, 8, 22280−22286
