Self-Supported Fe-Doped CoP Nanowire Arrays Grown on Carbon

Subscriber access provided by University of Rhode Island | University Libraries

Article

Self-Supported Fe-Doped CoP Nanowire Arrays Grown on Carbon Cloth with Enhanced Properties in Lithium-Ion Batteries Lianshan Ni, Gen Chen, Xiaohe Liu, Jiang Han, Xue Xiao, Ning Zhang, Shuquan Liang, Guanzhou Qiu, and Renzhi Ma ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.8b01437 • Publication Date (Web): 06 Dec 2018 Downloaded from http://pubs.acs.org on December 9, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Energy Materials

Self-Supported Fe-Doped CoP Nanowire Arrays Grown on Carbon Cloth with Enhanced Properties in Lithium-Ion Batteries Lianshan Ni,1 Gen Chen,1 Xiaohe Liu,1,* Jiang Han,1 Xue Xiao,1 Ning Zhang,1 Shuquan Liang,1 Guanzhou Qiu,2 Renzhi Ma3,* 1

State Key Laboratory of Powder Metallurgy and School of Materials Science and

Engineering, Central South University, Changsha, Hunan 410083, P. R. China. Email: [email protected] 2

School of Minerals Processing and Bioengineering, Central South University, Changsha,

Hunan 410083, P. R. China 3

International Center for Materials Nanoarchitectonics (MANA), National Institute for

Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan. E-mail: [email protected] ABSTRACT The development of novel materials for environmentally friendly and high energy density storage devices is important for a sustainable future. Herein, we demonstrate that binder-free Fe-doped CoP nanowire arrays/carbon cloth (Fe-CoP/CC) anode for lithium-ion batteries (LIBs), can be successfully synthesized via a simple hydrothermal process

combined

with

low-temperature

phosphorization

treatment.

Structural

characterizations display that Fe-CoP nanowires have a mean diameter of about 100 nm and an average length of about 5 μm. As-prepared Fe-CoP/CC presented obviously enhanced electrochemical properties over pristine CoP/CC, including high specific capacity up to 1320.7 mAh g–1 at 200 mA g–1, good stability with retention of 76.5% after 140 cycles, and superior rate capability of 525.3 mAh g–1 at 2 A g–1. The excellent electrochemical properties ACS Paragon Plus Environment

ACS Applied Energy Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

can be ascribed to the special 1D nanowire architecture, the in situ growth on conductive CC for free-standing anode, as well as the synergy and complementarity of Co and Fe ions. These results indicate that as-prepared Fe-CoP/CC is anticipated to be used in high-performance flexible LIBs and next-generation wearable energy storage systems. KEYWORDS: Fe-CoP, nanowires, carbon cloth, flexible, lithium storage INTRODUCTION As main power sources, lithium-ion batteries have been broadly applied to portable electronics, electric cars and other energy storage devices in daily life in virtue of their inherent advantages, i.e. high energy and power density, low power consumption, high cost performance and environmental friendliness.1-6 At present, traditional graphite is still the primary anode material in commercial LIBs application market, but the low theoretical capacity (~372 mAh g−1) makes it unable to satisfy the demands of high-performance energy storage devices. It is therefore urgent to find novel anode with high specific capacity.7-8 Transition metal phosphides,9 inheriting the advantages of the high theoretical capacity and relatively low working potential compared with oxides, sulfides and fluorides, have been widely researched as high-performance alternative anodes for LIBs application, such as FeP,10 Fe2P,11 CoP,12 MnP4,13 Cu3P.14 Among such phosphides, CoP is expected to be an alternative anode candidate owing to its high specific capacity of 894 mAh g−1, low discharge voltage platforms of about 0.6 V and good thermal stability.12, 15-16 Nevertheless, CoP usually suffers from rapid capacity fading caused by the huge volume variations during the charge/discharge process, causing the electrode material to pulverize, split, and fall off the current collector. Moreover, the low electronic conductivity and irreversibility of the electrochemical ACS Paragon Plus Environment

Page 2 of 24

Page 3 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


conversion reactions are also two barriers for commercialization of CoP in lithium ion batteries. Generally, there are two effective approaches to address the above problems. (1) Incorporating an appropriate amount of Fe element in CoP anode to improve its mechanical stability and electronic conductivity, contributing to good kinetics of Li+ insertion/extraction. Iron, benefiting from the strengths of cheapness and abundance, has been widely used in LIBs due to its rich redox reactions caused by abundant valence states (Fe0, Fe2+ and Fe3+) and environmental friendliness.17 Taking advantage of the synergy and complementarity between various elements, composites usually exhibit greater improvement in cyclic capacity and stability.18-22 (2) Fabricating nanostructured active materials (nanowire,23 nanorod,24 nanosheet25 et al.) directly on conductive current collectors, such as Cu foil, Ti foil, Ni foam and CC. Such optimized architecture has a tremendous surface area and open space, which can greatly reduce the diffusion distance of Li+ ions and alleviate the strain caused by volume variations in the Li+ ions insertion/extraction process. Besides, the in situ growth of active materials on the conductive substrate has a large binding force with the current collector, ensuring high structural stability of the electrode during cycling, leading to superior long-term cycling stability.26-28 Moreover, the electrode manufacturing process is also simplified without adding binder and conductive agent. Inspired by the above two strategies, the Fe-CoP/CC electrode is highly expected to possess superior electrochemical performance. Nevertheless, the study of Fe-CoP/CC electrode for LIBs application has not been reported. Herein, we demonstrate a simple synthetic approach to prepare Fe-CoP nanowire arrays directly grown on flexible CC. In such a hierarchical architecture, the ultrafine nanowires provide a full contact with electrolyte and abundant active sites, which can effectively reduce ACS Paragon Plus Environment


the transport path of Li+ ions and buffer volume expansions during the insertion/extraction of Li+ ions. In addition, CC as both the template and conductive current collector provides Li+ ions and electrons with fast transmission channel and decreases the contact resistance. Meanwhile, taking advantage of the synthetic and complementary effects between Co and Fe ions, Fe-CoP/CC as free-standing and binder-free electrode manifested enhanced lithium storage properties superior to CoP/CC electrode, including high charge/discharge capacity, improved long-term cycle stability and outstanding rate performance. EXPERIMENTAL SECTION Materials Synthesis: All the reagents (analytical grade) in the experiment are obtained from China National Pharmaceutical Group. Before the experiment, carbon cloth (CC, areal mass of 12.5 mg cm−2, thickness of 0.36 mm, WOS1002, CeThech co., Ltd) was cut into the size of 1×8 cm2 and then rinsed with concentrated nitric acid for two hours at room temperature to remove surface impurity. Then, the CC was ultrasonically washed with distilled water for several times. Fe-CoP/CC were prepared as following. In a typical synthesis, Fe(NO3)3·9H2O (0.404 g), Co(NO3)2·6H2O (0.582 g), NH4F (0.147 g) and urea (0.600 g) were added to 35 mL distilled water under constant stirring for 30 min at room temperature. Then, the pre-treated CC were transfereded to the homogeneous solution and maintained at 120 °C for 6 h. After the solution is completely reacted, the Co-Fe precursor/CC was washed with ethanol and distilled water for three times, then dried at 70 °C for 2 h. To obtain Fe-CoP/CC, the Co-Fe precursor/CC and 1 g NaH2PO2·H2O were placed at two different crucible, respectively. Then the crucible of NaH2PO2·H2O was putted on the upstream part and Co-Fe precursor/CC was putted on downstream part. Next, The tube furnace was heated to 300 °C from room

ACS Paragon Plus Environment

Page 4 of 24

Page 5 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


temperature with a ramping rate of 2 °C min−1 and maintained at 300 °C for 2 h in high-purity Ar. Finally, as-obtained Fe doped CoP nanowire arrays/CC samples were cleaned with distilled water. Similarly, CoP/CC is prepared while maintaining the otherwise identical experimental conditions as Fe-CoP/CC, except that Co precursor/CC is obtained by hydrothermal process at 100 °C for 12 hours without adding Fe(NO3)3·9H2O. The mass loading of as-prepared samples were about 2.5 mg cm–2. Structural Characterization: X-ray diffraction (XRD) analysis was used to characterize the crystal structure on Rigaku D/max 2500 diffractometer with Cu Ka radiation. The morphologies and microstructures were characterized with scan electron microscopy (SEM) on FEI Helios Nanolab 600i, transmission electron microscopy (TEM), selected area electron diffraction (SAED) pattern and high-resolution TEM (HRTEM) on FEI Tecnai G2 F20. X-ray photoelectron spectroscopy (XPS, ESCALAB250Xi) was applied to obtain the valence states. Electrochemical measurements: 2025 button cells were assembled in glovebox filled with argon to measure the electrochemical properties of Fe-CoP/CC electrode. Lithium metal is utilized as the counter and reference electrode, Fe-CoP/CC pieces with size of 1×1 cm2 were cut off and directly used as the working electrode. The electrolyte containing 1 mol L-1 LiPF6 solution in dimethyl carbonate/ethylene carbonate/diethyl carbonate (volume ratio of 1:1:1). The galvanostatic charge and discharge properties were performed on LANHE battery test system (CT2001A) at various current densities. Electrochemical impedance spectroscopy (EIS) and cyclic voltammogram (CV) were measured on CHI660E electrochemical workstation. RESULTS AND DISCUSSION



Free-standing Fe-doped CoP nanowire arrays on CC were synthesized via a facile growth approach, as shown in Figure 1. Firstly, the clean CC (Figure S1) was putted into a homogeneous solution containing Fe3+, Co2+ ions, as well as urea and ammonium fluoride, then the Fe-Co precursor nanowires were uniformly covered on the surface of CC through a facile hydrothermal reaction (Figure S2 and S3), finally converted to Fe-CoP/CC by a simple low-temperature phosphorization treatment. Figure 2a presents the XRD patterns of the CoP/CC and Fe-CoP/CC products. Both XRD patterns exhibit the similar characteristic peaks at 23.7°, 31.6°, 35.3°, 36.3°, 46.2°, 48.1°, 52.3° and 56.8°, which can be indexed to the (101), (011), (200), (111), (112), (211), (103) and (301) facets of orthorhombic CoP (JCPDS No.29-0497), respectively. Besides, the peaks at around 25.6° and 43.3° are attributed to the CC substrate.24 No extra diffraction peaks can be observed from impurity phases, implying that partial substitution of Co with Fe has no effect on the crystal phase of CoP because their atomic sizes are very close. The morphologies and detailed microstructures of as-prepared samples were investigated by SEM images, as shown in Figure 2b-f. Figure 2b, c show the SEM images with different magnifications of CoP/CC, in which the full and uniform coverage of CoP nanowires on the skeleton of the entire CC. Importantly, compared with Co precursor nanowires (Figure S3a, b), the morphology and integration of CoP nanowires were maintained even after the phosporization treatment. Note that the Fe-CoP/CC product presents similar nanostructure feature with CoP/CC, as shown in Figure 2d-f, the vertically oriented, large-scale, and uniform Fe-CoP nanowire arrays are grown on CC substrate. SEM image under high magnification (Figure 2f) clearly reveals that the diameter of nanowires is ~100 nm and the length is ~5 μm. After phosphating, the 1D nanowire arrays remain intact format. ACS Paragon Plus Environment

Page 6 of 24

Page 7 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


As shown in typical TEM image (Figure 3a), Fe-CoP nanowires show a conical structure that the diameter gradually decreases from root to tip. The HRTEM image of Fe-CoP nanowire displays several lattice fringes, as shown in Figure 3b, the measured interplanar distance is about 0.29 nm, which match well with the (011) plane of orthorhombic CoP. Several diffraction rings were observed in the SAED pattern (inset in Figure 3b), corresponding to the (011), (200), (211), and (103) facets of CoP, respectively, which is in line with the XRD results. The chemical compositions and corresponding elemental contents of Fe-CoP/CC samples were also investigated by EDX spectrum (Figure S4) and ICP-AES analysis (inset of Figure S4), manifesting the presence of Fe, Co, and P at an atomic ratio of about 1:2:3. The elemental maps (Figure 3c) further reveal that Co, Fe and P elements uniformly distributed in the Fe-CoP nanowire arrays. All these structural characterizations clearly indicate the formation of pure Fe-CoP/CC. Figure 4 displays the XPS spectra of Fe-CoP/CC. The full survey scan spectrum (Figure 4a) confirms that Fe-CoP/CC samples consists of C, O, Co, Fe elements consistent with the EDX observation. The Co 2p spectrum in Figure 4b presents two spin−orbit doublets. The first doublet at 778.9 and 793.8 eV attributes to the zero-valent Co in Fe-CoP/CC and the second at 782.0 and 797.8 eV belongs to oxidized Co, which is caused by the surface oxidation of Fe-CoP/CC with two satellite peak at 784.9 and 802.5 eV.29-30 Likewise, the Fe 2p spectrum (Figure 4c) is also deconvoluted into two spin-orbit doublets. One doublet appears at 710.8 and 722.0 eV is mainly ascribed to Fe2+ ion while the other doublet at 714.5 and 726.0 eV is attributed to Fe3+ ion.30-31 No characteristic peak of FeP appeared in the Fe 2p spectrum, manifesting that a ternary Fe-CoP is formed. Figure 4d shows the P 2p spectra, in which the peaks ascribed to the phosphide at 129.6 and 130.2 eV are come from P 2p1/2 and P ACS Paragon Plus Environment


2p3/2,32-33 respectively. Moreover, the broad peak observed at 134.0 eV is attributed to the oxidized P caused by the surface oxidation from direct air contact of Fe-CoP/CC.30, 34 CV at a scan rate of 0.1 mV s−1 within the potential region of 3.0–0.01 V (vs Li+/Li) was carried out to characterize the electrochemical behavior of the CoP/CC and Fe-CoP/CC anodes. The CV curves of CoP/CC electrode were measured for three cycles and shown in Figure 5a, the observed oxidation peak appears at ~0.3 V and the reduction peak appears at around 0.1 V are caused by the effect of CC.24, 35 During the first cathodic sweep, a broad peak observed at about 1.1 V corresponds to the reduction of CoP + 3Li+ + 3e− → Co + Li3P.12, 36 Besides, a weak peak appears at about 0.6 V is related to the reduction of CoP + Li+ + e− → LiP + Co,12,

36-37

and the small peak centers at around 0.5 V is ascribed to some

irreversible reaction along with the generation of solid electrolyte interphase (SEI) layer.12 In the first charge scan, two anodic peaks locate at around 1.0 and 1.2 V could be observed because of the oxidation of Li3P.15,

38

Two pairs of clear oxidation/reduction peaks are

observed in the subsequent CV curves, corresponding to the reversible redox between Li3P and LiP:12 Li3P 

LiP + 2Li+ + 2e−. After the first charge/discharge reaction, the overlapped

curves adumbrate the good electrochemical reversibility and stability of CoP/CC anode. Notably, the CV curve of Fe-CoP/CC anode is similar to CoP/CC, implying the influence of Fe introduction on the redox reaction can be neglected (Figure 5b). More importantly, the CV curves of Fe-CoP/CC become more stable after initial cycle than that of CoP/CC, indicating that Fe doping induces better electrochemical reaction kinetics. Figure 5c and d show the capacity–voltage plots with various cycles of the pure CoP/CC and Fe-CoP/CC electrodes at 100 mA g−1 from 0.01 V to 3.0 V at room temperature, respectively. The pure CoP/CC and Fe-CoP/CC electrodes display close first discharge ACS Paragon Plus Environment

Page 8 of 24

Page 9 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


capacities up to 1587.5 and 1584.3 mAh g−1, and the corresponding coulombic efficiencies of 84.7% and 83.6%, respectively. The SEI film produced by the decomposition of electrolyte can explain the phenomenon of large capacity loss observed in the initial cycle. The subsequent charge/discharge capacities tend to be stable and reversible, Fe-CoP/CC shows high reversible capacity of 1324.9, 1071.9, 1141.0 mAh g–1 at the 2nd, 50th, 100th cycles, respectively, and superior capacity retention ratio of 86.1 % (relative to the second discharge capacity) after 100 cycles better than that of CoP/CC (64.6 % after 100th cycle). The cycling performance and Coulombic efficiency of CoP/CC and Fe-CoP/CC electrodes at 200 mA g−1 were investigated and shown in Figure 5e. Fe-CoP/CC anode shows an initial Coulombic efficiency of 84.4% because of the generation of SEI layers, then quickly raises to 97% in the 2nd cycle and holds nearly 100% in the subsequent cycles, demonstrating perfect charge/discharge reversibility. Note that the capacities of Fe-CoP/CC electrode gradually decrease in the first several charge-discharge cycles, then stabilize in the following cyclic processes, which is related to the slow kinetic activation process of Fe-CoP/CC electrode. In addition, Fe-CoP/CC electrode exhibits enhanced cycling stability, a high reversible capacity of 1010.6 mAh g–1 is obtained in the 140th cycle, which is equivalent to 76.5% of the second discharge capacity (1320.7 mAh g–1). Comparatively, without Fe doping, pristine CoP/CC anode exhibits a severe capacity decay during cycling together with a poor capacity of 371 mAh g−1 in the 140th cycle (capacity retention of only 28%). The improved cycling stability of the Fe introduction is related to the synthetic and complementary effects between Co and Fe ions, which leads to good mechanical stability and electronic conductivity of Fe-CoP/CC anode during cycling. In addition, the electrochemical performance and characteristic of those previous reported transition-metal phosphides anodes were compared with our work (Table ACS Paragon Plus Environment


S1). As-prepared Fe-CoP/CC anode in this work shows much improved lithium storage properties comparing with most of the reported transition-metal phosphides anodes. The charge/discharge capacities of clean CC during cycling were also compared with Fe-CoP/CC electrode at 100 mA g−1, as shown in Figure S5. The clean CC (12.5 mg) provides a discharge capacity of 1.25 mAh cm−2, while Fe-CoP/CC (The mass of Fe-CoP sample is 2.5 mg) exhibits a high discharge capacity of 3.3 mAh cm−2 in the second cycle, and high reversible capacity of 2.85 mAh cm−2 is retained after 100 cycles. Furthermore, as shown in Figure 5f, the rate performance of Fe-CoP/CC electrode is also much better than pristine CoP/CC from 100 mA g−1 to 2000 mA g−1, which shows average reversible capacities of 1218.3, 1020, 859.9, 706.3, and 525.3 mAh g−1 at the increasing current of 100, 200, 500, 1000, and 2000 mA g−1, respectively. Even cycled at a large current rate of 2000 mA g−1, Fe-CoP/CC electrode still retains 43% of the initial reversible capacity. Notably, when sets back to initial current of 100 mA g−1, the discharge capacity of Fe-CoP/CC electrode can still be stabilized at 1073 mAh g−1, while CoP/CC electrode shows a rapid capacity decay, indicating improved rate property of Fe-CoP/CC anode. Apparently, the gap of discharge capacity between two electrodes also increases along with the increase of current density, which clearly exhibits better rate capability of the Fe-doped CoP/CC than pristine CoP/CC electrode. EIS analysis is utilized to further investigate the charge transport kinetics of both fresh electrode and 100-cycled at 100 mA g–1 electrode for the CoP/CC and Fe-doped CoP/CC, as shown in Figure S6. Both Nyquist plots show similar shape: the high-frequency semicircle is ascribed to the electrochemical reaction occurred in the interface between the electrode and electrolyte, and the corresponding diameter of the semicircle represents the value of charge ACS Paragon Plus Environment

Page 10 of 24

Page 11 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


transfer resistance (Rct). The low-frequency inclined straight line is attributed to the diffusion resistance within the electrode materials, and the corresponding slope of the straight line is related to the value of Warburg resistances. Variations in the corresponding fitting parameters of EIS curves for both electrodes are shown in Table S2. Fe-doped CoP/CC electrode shows significantly reduced Rct comparing with that of pristine CoP/CC before and after charge/discharge reaction, indicating lower charge transfer impedance in the Fe-doped CoP/CC composites. This may be attributed to the partial doping of Fe ions in the CoP/CC, contributing to good electronic conductivity and electron transfer kinetics. It is worth noting that both 100-cycled electrodes exhibit much lower Rct than the fresh electrodes, which can be ascribed to the activation process along with the cycling.

CONCLUSION To conclude, Fe-CoP nanowire arrays directly grown on CC as free-standing anode materials for LIBs were successfully fabricated via a facile and cost-effective approach. Compared with the pristine CoP/CC, Fe-CoP/CC presents much better electrochemical properties, which is ascribed to the reduced Li+ transport path, the in situ growth on conductive carbon cloth for free-standing electrode, as well as the synergy and complementarity of Co and Fe ions. Besides, part of Fe doping in the electrode material can be more cost-effective and environmentally friendly due to the cheapness and low-toxicity of Fe element. It is anticipated that the as-fabricated Fe-CoP/CC may consist of good contribution in the development of phosphides anode for LIBs, which offers potential opportunities for practical applications in high-performance energy storage and future wearable electronic devices.

ASSOCIATED CONTENT ACS Paragon Plus Environment


Supporting Information. This material is available free of charge via the Internet at http://pubs.acs.org. Experimental sections, Schematic illustration, XRD, SEM, EDX, ICP, XPS data and additionally electrochemical measurements for Co and Co-Fe precursor, CoP and Fe-CoP grown on the CC.

AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected]; *E-mail: [email protected] Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT L.N. and G.C. contributed equally to this work. The authors acknowledge the financial support by National Natural Science Foundation of China (51874357, 51872333). X. L. acknowledges support from Shenghua Scholar Program of Central South University. R. M. acknowledges support from JSPS KAKENNHI (15H03534, 15K13296).

REFERENCES


Page 12 of 24

Page 13 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(1) Jeong, G.; Kim, Y.-U.; Kim, H.; Kim, Y.-J.; Sohn, H.-J., Prospective Materials and Applications for Li Secondary Batteries. Energy Environ. Sci. 2011, 4, 1986-2002. (2) Tang, Y.; Zhang, Y.; Li, W.; Ma, B.; Chen, X., Rational Material Design for Ultrafast Rechargeable Lithium-Ion Batteries. Chem. Soc. Rev. 2015, 44, 5926-5940. (3) Chen, G.; Yan, L.; Luo, H.; Guo, S., Nanoscale Engineering of Heterostructured Anode Materials for Boosting Lithium-Ion Storage. Adv. Mater. 2016, 28, 7580-7602. (4) Shen, L.; Liu, F.; Chen, G.; Zhou, H.; Le, Z.; Wu, H. B.; Wang, G.; Lu, Y., Encapsulation of SnO2 Nanocrystals into Hierarchically Porous Carbon by Melt Infiltration for High-Performance Lithium Storage. J. Mater. Chem. A 2016, 4, 18706-18710. (5) Huang, X.; Sui, X.; Yang, H.; Ren, R.; Wu, Y.; Guo, X.; Chen, J., HF-free Synthesis of Si/C Yolk/Shell Anodes for Lithium-Ion Batteries. J. Mater. Chem. A 2018, 6, 2593-2599. (6) Feng, K.; Li, M.; Liu, W.; Kashkooli, A. G.; Xiao, X.; Cai, M.; Chen, Z., Silicon-Based Anodes for Lithium-Ion Batteries: from Fundamentals to Practical Applications. Small 2018, 14, 201702737. (7) Chen, G.; Wang, S.; Yi, R.; Tan, L.; Li, H.; Zhou, M.; Yan, L.; Jiang, Y.; Tan, S.; Wang, D.; Deng, S.; Meng, X.; Luo, H., Facile Synthesis of Hierarchical MoS2-carbon Microspheres as a Robust Anode for Lithium Ion Batteries. J. Mater. Chem. A 2016, 4, 9653-9660. (8) Poizot, P.; Laruelle, S.; Grugeon, S.; Dupont, L.; Tarascon, J. M., Nano-sized ACS Paragon Plus Environment


Transition-Metal Oxides as Negative-Electrode Materials for Lithium-Ion Batteries. Nature 2000, 407, 496-499. (9) Cabana, J.; Monconduit, L.; Larcher, D.; Palacin, M. R., Beyond Intercalation-Based Li-Ion Batteries: The State of The Art and Challenges of Electrode Materials Reacting through Conversion Reactions. Adv. Mater. 2010, 22, E170-E192. (10) Han, F.; Zhang, C.; Yang, J.; Ma, G.; He, K.; Li, X., Well-dispersed and Porous FeP@C Nanoplates With Stable and Ultrafast Lithium Storage Performance through Conversion Reaction Mechanism. J. Mater. Chem. A 2016, 4, 12781-12789. (11) Zhang, Y.; Zhang, H.; Feng, Y.; Liu, L.; Wang, Y., Unique Fe2P Nanoparticles Enveloped in Sandwich like Graphited Carbon Sheets as Excellent Hydrogen Evolution Reaction Catalyst and Lithium-Ion Battery Anode. ACS Appl. Mater. Interfaces 2015, 7, 26684-26690. (12) Yang, D.; Zhu, J.; Rui, X.; Tan, H.; Cai, R.; Hoster, H. E.; Yu, D. Y.; Hng, H. H.; Yan, Q., Synthesis of Cobalt Phosphides and Their Application as Anodes for Lithium Ion Batteries. ACS Appl. Mater. Interfaces 2013, 5, 1093-1099. (13) Souza, D. C. S.; Pralong, V.; Jacobson, A. J.; Nazar, L. F., A Reversible Solid-State Crystalline Transformation in a Metal Phosphide Induced by Redox Chemistry. Science 2002, 296, 2012-2015. (14) Ni, S.; Ma, J.; Lv, X.; Yang, X.; Zhang, L., The Fine Electrochemical Performance of Porous Cu3P/Cu and The High Energy Density of Cu3P as Anode for Li-Ion Batteries. J. Mater. Chem. A 2014, 2, 20506-20509.


Page 14 of 24

Page 15 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(15) Jiang, J.; Wang, C.; Li, W.; Yang, Q., One-pot Synthesis of Carbon-coated Ni5P4 Nanoparticles and CoP Nanorods for High-Rate and High-Stability Lithium-Ion Batteries. J. Mater. Chem. A 2015, 3, 23345-23351. (16) Xu, X.; Liu, J.; Hu, R.; Liu, J.; Ouyang, L.; Zhu, M., Self-Supported CoP Nanorod Arrays Grafted on Stainless Steel as an Advanced Integrated Anode for Stable and Long-Life Lithium-Ion Batteries. Chem.-Eur. J. 2017, 23, 5198-5204. (17) Yu, S.; Hong Ng, V. M.; Wang, F.; Xiao, Z.; Li, C.; Kong, L. B.; Que, W.; Zhou, K., Synthesis and Application of Iron-Based Nanomaterials as Anodes of Lithium-Ion Batteries and Supercapacitors. J. Mater. Chem. A 2018, 6, 9332-9367. (18) Mohamed, S. G.; Chen, C. J.; Chen, C. K.; Hu, S. F.; Liu, R. S., High-performance Lithium-Ion Battery And Symmetric Supercapacitors Based on FeCo2O4 Nanoflakes Electrodes. ACS Appl. Mater. Interfaces 2014, 6, 22701-22708. (19) Ni, L.; Jia, L.; Chen, G.; Wang, F.; Liu, X.; Ma, R., Facile Synthesis of Porous FeCo2O4 Nanowire Arrays on Flexible Carbon Cloth with Superior Lithium Storage Properties. J. Phys. Chem. Solids 2018, 122, 261-267. (20) Xing, Z.; Ju, Z.; Yang, J.; Xu, H.; Qian, Y., One-step Hydrothermal Synthesis of ZnFe2O4 Nano-Octahedrons as a High Capacity Anode Material for Li-Ion Batteries. Nano Res. 2012, 5, 477-485. (21) Cherian, C. T.; Sundaramurthy, J.; Reddy, M. V.; Suresh, K. P.; Mani, K.; Pliszka, D.; Sow, C. H.; Ramakrishna, S.; Chowdari, B. V., Morphologically robust NiFe2O4 nanofibers as high capacity Li-ion battery anode material. ACS Appl. Mater. Interfaces



2013, 5, 9957-9963. (22) Xiong, Q. Q.; Tu, J. P.; Shi, S. J.; Liu, X. Y.; Wang, X. L.; Gu, C. D., Ascorbic Acid-Assisted Synthesis of Cobalt Ferrite (CoFe2O4) Hierarchical Flower-Like Microspheres with Enhanced Lithium Storage Properties. J. Power Sources 2014, 256, 153-159. (23) Jiang, J.; Liu, J.; Ding, R.; Ji, X.; Hu, Y.; Li, X.; Hu, A.; Wu, F.; Zhu, Z.; Huang, X., Direct Synthesis of CoO Porous Nanowire Arrays on Ti Substrate and Their Application as Lithium-Ion Battery Electrodes. J. Phys. Chem. C 2010, 114, 929-932. (24) Ni, L.; Tang, W.; Liu, X.; Zhang, N.; Wang, J.; Liang, S.; Ma, R.; Qiu, G., Hierarchical CoO/MnCo2O4.5 Nanorod Arrays on Flexible Carbon Cloth as High-Performance Anode Materials for Lithium-Ion Batteries. Dalton Trans. 2018, 47, 3775-3784. (25) Long, H.; Shi, T.; Hu, H.; Jiang, S.; Xi, S.; Tang, Z., Growth of Hierarchal Mesoporous NiO Nanosheets on Carbon Cloth as Binder-Free Anodes for High-Performance Flexible Lithium-Ion Batteries. Sci. Rep. 2014, 4, 7413. (26) Shen, L.; Che, Q.; Li, H.; Zhang, X., Mesoporous NiCo2O4 Nanowire Arrays Grown on Carbon Textiles as Binder-Free Flexible Electrodes for Energy Storage. Adv. Funct. Mater. 2014, 24, 2630-2637. (27) Cao, K.; Jiao, L.; Liu, Y.; Liu, H.; Wang, Y.; Yuan, H., Ultra-High Capacity Lithium-Ion Batteries with Hierarchical CoO Nanowire Clusters as Binder Free Electrodes. Adv. Funct. Mater. 2015, 25, 1082-1089. (28) Liu, L.; Zhang, H.; Mu, Y.; Yang, J.; Wang, Y., Porous Iron Cobaltate Nanoneedles ACS Paragon Plus Environment

Page 16 of 24

Page 17 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Array on Nickel Foam as Anode Materials for Lithium-Ion Batteries with Enhanced Electrochemical Performance. ACS Appl. Mater. Interfaces 2016, 8, 1351-1359. (29) Tang, C.; Zhang, R.; Lu, W.; He, L.; Jiang, X.; Asiri, A. M.; Sun, X., Fe-Doped CoP Nanoarray: a Monolithic Multifunctional Catalyst for Highly Efficient Hydrogen Generation. Adv. Mater. 2017, 29, 1602441. (30) Tang, C.; Gan, L.; Zhang, R.; Lu, W.; Jiang, X.; Asiri, A. M.; Sun, X.; Wang, J.; Chen, L., Ternary FexCo1-xP Nanowire Array as a Robust Hydrogen Evolution Reaction Electrocatalyst with Pt-like Activity: Experimental and Theoretical Insight. Nano Lett. 2016, 16, 6617-6621. (31) Long, X.; Li, G.; Wang, Z.; Zhu, H.; Zhang, T.; Xiao, S.; Guo, W.; Yang, S., Metallic Iron-Nickel Sulfide Ultrathin Nanosheets as a Highly Active Electrocatalyst for Hydrogen Evolution Reaction in Acidic Media. J. Am. Chem. Soc. 2015, 137, 11900-11903. (32) Liu, T.; Ma, X.; Liu, D.; Hao, S.; Du, G.; Ma, Y.; Asiri, A. M.; Sun, X.; Chen, L., Mn Doping of CoP Nanosheets Array: an Efficient Electrocatalyst for Hydrogen Evolution Reaction with Enhanced Activity at All pH Values. ACS Catal. 2016, 7, 98-102. (33) Tian, J.; Liu, Q.; Asiri, A. M.; Sun, X., Self-supported Nanoporous Cobalt Phosphide Nanowire Arrays: an Efficient 3D Hydrogen-Evolving Cathode over The Wide Range of pH 0-14. J. Am. Chem. Soc. 2014, 136, 7587-7590. (34) Hao, S.; Yang, L.; Liu, D.; Kong, R.; Du, G.; Asiri, A. M.; Yang, Y.; Sun, X., Integrating Natural Biomass Electro-Oxidation And Hydrogen Evolution: Using a



Porous Fe-Doped CoP Nanosheet Array as a Bifunctional Catalyst. Chem. Commun. 2017, 53, 5710-5713. (35) Mo, Y.; Ru, Q.; Chen, J.; Song, X.; Guo, L.; Hu, S.; Peng, S., Three-dimensional NiCo2O4 Nanowire Arrays: Preparation and Storage Behavior for Flexible Lithium-Ion and Sodium-Ion Batteries with Improved Electrochemical Performance. J. Mater. Chem. A 2015, 3, 19765-19773. (36) Guo, G.; Guo, Y.; Tan, H.; Yu, H.; Chen, W.; Fong, E.; Yan, Q., From Fibrous Elastin Proteins to One-Dimensional Transition Metal Phosphides and Their Applications. J. Mater. Chem. A 2016, 4, 10893-10899. (37) Yang, J.; Zhang, Y.; Sun, C.; Liu, H.; Li, L.; Si, W.; Huang, W.; Yan, Q.; Dong, X., Graphene and Cobalt Phosphide Nanowire Composite as an Anode Material For High Performance Lithium-Ion Batteries. Nano Res. 2016, 9, 612-621. (38) Wang, B.; Ru, Q.; Guo, Q.; Chen, X.; Wang, Z.; Hou, X.; Hu, S., Fabrication of One-Dimensional Mesoporous CoP Nanorods as Anode Materials for Lithium-Ion Batteries. Eur. J. Inorg. Chem. 2017, 3729-3735.


Page 18 of 24

Page 19 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure

Figure 1. Schematic illustration for the preparation of the CoP/CC and Fe-CoP/CC.



Figure 2. (a) XRD patterns for CoP/CC and Fe-CoP/CC. SEM micrographs with different magnifications for (b, c) CoP/CC, (d, e, f) Fe-CoP/CC.


Page 20 of 24

Page 21 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3. (a) TEM micrograph, (b) HRTEM micrograph of the Fe-CoP nanowires (inset shows the corresponding SAED pattern); (c) STEM micrograph and the corresponding elemental maps of cobalt, ferrum and phosphorous.



Figure 4. (a) Survey scan spectrum of Fe-CoP/CC. (b, c, d) XPS spectra of Co 2p, Fe 2p, and P 2p, respectively.


Page 22 of 24

Page 23 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5. CV curves: (a) CoP/CC, (b) Fe-CoP/CC electrodes from 0.01 to 3.0 V at 0.1 mV s– 1.

Charge-discharge curves: (c) CoP/CC, (d) Fe-CoP/CC electrodes at 100 mA g–1. (e) Cycling

performances of CoP/CC and Fe-CoP/CC electrodes at 200 mA g–1. (f) Rate performances of CoP/CC and Fe-CoP/CC electrodes from 0.1 to 2 A g–1.


ACS Applied Energy Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 24


Page 24 of 24

Self-Supported Fe-Doped CoP Nanowire Arrays Grown on Carbon

Recommend Documents