Phosphorus-Rich CuP2 Embedded in ... - ACS Publications

Research Article www.acsami.org

Phosphorus-Rich CuP2 Embedded in Carbon Matrix as a HighPerformance Anode for Lithium-Ion Batteries Sang-Ok Kim† and Arumugam Manthiram* Materials Science and Engineering Program & Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States S Supporting Information *

ABSTRACT: Phosphorus-rich CuP2 and its carbon composites have been investigated as an anode material for lithiumion batteries. Through a facile, low-cost mechanochemical reaction, microsized composites composed of active CuP2 particles uniformly embedded in the carbon matrix have been successfully synthesized. Combined structural and electrochemical characterizations show that phosphorus-rich CuP2 undergoes irreversible reaction with lithium, giving metal-rich Cu3P and amorphous phosphorus at the end of the first cycle. Both Cu3P and phosphorus are reversibly formed in subsequent cycles, contributing to a high reversible capacity of >1000 mA h g−1. By controlling the carbon content, the electrochemical reversibility and stability of CuP2 are greatly improved. The carbon composite demonstrates a remarkable lithium-storage capability in terms of a stable capacity of >720 mA h g−1 over 100 cycles at 200 mA g−1, a high initial Coulombic efficiency of ∼83%, and a good rate capability with a capacity of >637 mA h g−1 at 1.6 A g−1. The performance improvement is mainly associated with the formation of the conductive carbon network that offers high conductivity and fast reaction kinetics, as well as enhanced structural stability of CuP2 anode. KEYWORDS: lithium-ion batteries, anode, copper phosphide, carbon composite, mechanical milling mA h g−1, which is comparable to graphite. In this regard, the utilization of phosphorus-rich CuP2 seems to be more promising in order to realize a high capacity anode material. Nevertheless, unlike metal-rich Cu3P, electrochemical studies of CuP2 anodes for lithium-ion batteries have been rarely reported to date.20 Despite much higher theoretical capacity of ∼1280 mA h g−1, CuP2 has low electronic conductivity and also inevitably suffers from large volume change during the lithiation and delithiation processes derived from the high phosphorus content in CuP2, which eventually leads to rapid capacity fade and poor rate capability upon repeated cycling. Our previous study showed the simple preparation and enhanced sodium-storage performance of phosphorus-rich CuP2, which was incorporated into the nanoscale carbon framework.21 The electrochemical performance of the synthesized CuP2/C composite was significantly improved by preserving good electrical conduction pathways through the strong P−O−C bonds formed on the surface of the composite particles and by mitigating the volume expansion of the active materials with the aid of the electrochemically stable carbon buffer matrix. Considering that the volume expansion of phosphorus in CuP2 upon lithiation (Li3P, ∼300%) is much

1. INTRODUCTION Considerable efforts are being made to develop high capacity anode materials for lithium-ion batteries in order to replace the currently used graphite anode with limited theoretical capacity (LiC6: 372 mA h g−1) and safety concerns.1,2 Various conversion-type transition-metal phosphides (MPx, M = Fe, Co, Ni, and Cu) have been widely investigated as possible alternatives due to their high specific capacities based on the reversible reaction between phosphorus and lithium (Li3P, 2596 mA h g−1).3−10 Upon lithiation, the MPx systems undergo the conversion reactions (MPx + 3xLi → xLi3P + M), leading to the formation of composites composed of metallic phase and Li3P. Although the use of phosphorus itself has resulted in poor electrochemical performance originating from a large volume variation (∼300%) occurring upon lithiation/delithiation and a low electronic conductivity (10−14 S cm−1),11,12 these MPx systems have shown enhanced cycling stability and rate capability since the extracted metal particles provide high conductivity and volume buffering effects over cycling. Copper phosphides are conversion-type phosphides in lithium-ion cells. Among the two binary compositions of Cu3P and CuP2, metal-rich Cu3P has been intensively studied for its good electrochemical performances such as high volumetric capacity and good cyclability.13−19 However, because of the high content of an inactive copper phase in Cu3P, it exhibits only a limited gravimetric capacity of ∼390 © XXXX American Chemical Society

Received: February 26, 2017 Accepted: April 27, 2017 Published: April 27, 2017 A

DOI: 10.1021/acsami.7b02826 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces smaller than that upon sodiation (Na3P, ∼490%),22,23 the developed CuP2-based composite is expected to more effectively overcome the above-mentioned drawbacks related to conductivity and structural stability issues. Therefore, in this study, we report the electrochemical performance of the CuP2/ C composite in lithium-ion batteries. By virtue of the simple confinement of CuP2 active materials in multifunctional carbon buffer matrix, the CuP2/C composite demonstrates outstanding lithium-storage performance including a high reversible capacity and long-term cyclability, as well as good charge−discharge rate capability, making it a potential anode material for highperformance lithium-ion batteries.

2. EXPERIMENTAL SECTION

Figure 1. XRD patterns of pure CuP2 and CuP2/C composites prepared by HEMM for 3 h.

2.1. Sample Preparation. Pure CuP2 and the CuP2/C composites were synthesized with a one-step high-energy mechanical milling (HEMM) method. The detailed preparation method is given in the previous study.21 Briefly, stoichiometric amounts of commercial copper (99%, 45 μm, Acros Organics) and red phosphorus (98+%, Alfa Aesar) were mixed with an atomic ratio of 1:2. Then, the mixture was put into a hardened steel vial (80 cm3) with hardened steel balls along with three different amounts of acetylene black (10, 20, and 30 wt %). After sealing in an argon-filled glovebox, HEMM was performed with a SPEX 8000 M apparatus for 3 h. The total weight of the powder was adjusted to 2.0 g with a ball-to-powder mass ratio of 20:1. The as-prepared composite samples were ground and stored in an argon-filled glovebox. 2.2. Sample Characterization. The crystal structure and chemical state of the composite samples were characterized with X-ray diffraction (XRD; Rigaku MiniFlex 600) with Cu Kα radiation. Scanning electron microscopy (SEM; JEOL JSM-5610) combined with energy dispersive X-ray spectroscopy (EDS) was utilized to analyze the particle morphology and elemental composition of the samples. The tap density was estimated with a Quantachrome AT-4 Autotap apparatus. 2.3. Electrochemical Measurements. For the preparation of the electrodes, slurries consisting of 70 wt % active material (CuP2 and acetylene black), 15 wt % conductive additive (Super P), and 15 wt % poly(acrylic acid) (PAA) binder (MW ∼ 250,000, Aldrich) were mixed thoroughly, pasted onto a copper foil current collector with the doctor blade method, and dried in a vacuum oven at 120 °C for 8 h. Then, the electrodes were punched into disks (diameter, 1.2 cm) with a typical active mass loading of 1.8−2.0 mg cm−2 and a thickness of ∼40 μm. The CR2032 coin cells were assembled inside an argon-filled glovebox by sandwiching a polypropylene (Celgard 2500) separator between the test electrode and a lithium metal counter/reference electrode. The electrolyte used for the electrochemical tests is composed of 1.0 M LiPF6 dissolved in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC; 1:1 (v/v)) with 5 vol % fluoroethylene carbonate (FEC). Constant-current cycling tests were performed with an Arbin battery cycler (BT-2000) within a potential range between 0.0 and 2.0 V (vs Li/Li+). Electrochemical impedance spectroscopy (EIS) studies were conducted with an impedance/gain-phase analyzer (Solartron SI 1260A) equipped with an electrochemical interface (Solartron SI 1287A). For ex situ measurements, the cycled electrodes were obtained by disassembling the coin cells, washing with DEC, and drying naturally under an argon atmosphere.

are observed in all the composite samples, suggesting that carbon remained in its amorphous form within the composite powders. The intensity of CuP2 peaks decreases with increasing carbon content, which indicates the reduction of the mean crystallite size of the CuP2 particles in the carbon composites. It should be noted that the carbon composites possess stable local P−O−C bonds formed by the reaction between a native oxide on the phosphorus surface and carbon precursor during HEMM, as demonstrated in our previous work,21 possibly leading to enhanced electrochemical performance in lithiumion cells. The SEM images given in Figure 2 reveal that all the assynthesized materials have a similar morphology of secondary

Figure 2. SEM images of (a) pure CuP2 and CuP2-based composites with (b) 10, (c) 20, and (d) 30 wt % carbon.

particles with irregular shapes due to the continuous fracture and welding processes during ball milling.24 Although similar particle sizes ranging from a few hundred nanometers to a few micrometers are observed for all the CuP2-based materials, it seems that the carbon composites (Figure 2b−d) generally show smaller particle sizes than pure CuP2 (Figure 2a), with the presence of well-dispersed nanosized carbon particles. The overall micrometer-sized nature of these particles could be translated into high powder tap density as well as high volumetric capacity, which are becoming more crucial for commercialization.25−28 The measured tap densities of the CuP2/C composites were ∼1.27, ∼1.2, and ∼1.1 g cm−3, respectively, for the 10, 20, and 30 wt % carbon-containing

3. RESULTS AND DISCUSSION Figure 1 presents the XRD patterns of pure CuP2 and the CuP2/C composites prepared by HEMM for 3 h. All the samples show the diffraction peaks corresponding to the crystalline CuP2 phase (JCPDS No. 76-1190), indicating the successful production of CuP2 during synthesis without any other Cu−P binary phases and residual metallic copper and phosphorus precursors. Moreover, no peaks related to carbon B


Research Article

ACS Applied Materials & Interfaces

similar trend, with the values of ∼86, ∼83, and ∼81%, respectively, for 10, 20, and 30 wt % carbon composite samples. The decrease in the CEs of the carbon composites in the first cycle originates from the increasing amounts of acetylene carbon black matrices because they generally result in the large irreversible capacity loss by adsorbing and trapping lithium ions within the structure during the first discharge process.31−33 Although the addition of carbon leads to the decrease in delithiation capacity of the CuP2/C composites compared to that of pure CuP2, the CuP2/C composites still deliver much higher capacity than graphite and exhibit significantly reduced overpotential in the initial discharge process due to the formation of a conductive carbon network. Moreover, in the subsequent cycle, all CuP2/C composite electrodes display more sloping potential profiles with smaller polarization between the charge and discharge processes compared to the pure CuP2 electrode, which might enhance the electrochemical performance of the composite electrodes. In order to better understand the reaction mechanism of CuP2 in lithium-ion cells, the differential capacity plots (DCPs) of the CuP2/C (20 wt %) composite were obtained for the first two cycles and ex situ XRD measurements were conducted at several states of charge. From the DCP curve in Figure 4a, there

samples, exceeding that of commonly used graphite anode material (∼1.0 g cm−3).29,30 According to the details on the microstructure of the synthesized CuP2/C composite provided in our previous study,21 the composite materials are composed of agglomerated nanoscale CuP2 active particles uniformly intermixed with conductive carbon matrix. As a result of the homogeneous distribution of phosphorus-rich CuP2 and carbon (Supporting Information Figure S1), it can be expected that the CuP2/C composites exhibit improved cycling stability and rate capability, as well as good electrochemical reversibility. In the SEM/EDS data of pure CuP2 and CuP2/C (20 wt %) composite (Figure S2), both samples show that the atomic ratio of copper to phosphorus is nearly 1:2. This further confirms the formation of phosphorus-rich CuP2 after HEMM with and without carbon, in accordance with the XRD analysis (Figure 1). The presence of conductive carbon buffer matrix in the composite samples can alleviate large volume change of active material (CuP2) during cycling and decrease the lithiumion diffusion distance, facilitating the lithiation and delithiation processes. The voltage profiles of the pure CuP2 and CuP2/C composite electrodes for the first two cycles tested at a current rate of 100 mA g−1 between 0.0 and 2.0 V (vs Li/Li+) are shown in Figure 3. The first discharge (lithiation) and charge

Figure 3. Voltage profiles of pure CuP2 and CuP2/C composites for initial two cycles at a current density of 100 mA g−1 between 0.0 and 2.0 V (vs Li/Li+).

Figure 4. (a) DCP curves for initial two cycles and (b) ex situ XRD patterns of the CuP2/C (20 wt %) composite taken at various states of charge indicated in (a) (1) OCV, (2) 0 V, (3) 1.15 V, (4) 2.0 V, (5) 0.85 V, (6) 0 V, (7) 1.15 V, and (8) 2.0 V.

(delithiation) capacities of the pure CuP2 electrode are, respectively, ∼1260 and ∼1040 mA h g−1, with a high initial Coulombic efficiency (CE) of ∼83%. The specific delithiation capacity of pure CuP2 is about three times greater than that of graphite due to the high phosphorus content in the CuP2 binary alloy. For the carbon composites, the first discharge capacities decrease with an increasing amount of carbon in the CuP2/C composites. The obtained values were ∼946, ∼ 836, and ∼749 mA h g−1, respectively, for the samples with 10, 20, and 30 wt % carbon as displayed in Figure 3. The specific capacities were calculated based on the total weight of the composites. At the same time, the initial CEs also show a

is only a sharp peak at ∼0.57 V upon first discharge, which is associated with the formation of Li3P by the lithiation reaction of phosphorus that is generated from the dissociation of CuP2 into metallic copper and phosphorus.20 This can be confirmed by ex situ XRD pattern in Figure 4b. The copper peaks are not detectable, probably due to the nanosized nature of the extracted copper. In the following charge step, two sharp peaks can be observed at ∼1.09 and ∼1.25 V, indicating the stepwise delithiation processes from Li3P to phosphorus (Li3P → Li2CuP → P).20 It is interesting to note that the final phase that C


Research Article

ACS Applied Materials & Interfaces appeared at full delithiation (2.0 V) was metal-rich Cu3P rather than phosphorus-rich CuP2 in lithium half-cells, unlike the reversible formation of CuP2 during sodiation and desodiation in sodium half-cells.21 The remaining phosphorus is believed to be present in its amorphous form in the electrode at the end of the first cycle. During the second discharge process, the sharp peak at ∼0.57 V disappears and two other peaks located at ∼0.89 and ∼0.78 V are newly evolved, which are attributed to, respectively, the formation of Li2CuP and Li3P. In addition, the following DCP curve shows exactly the same shape as that in the first delithiation process, meaning that Li2CuP, Cu3P, and amorphous phosphorus phases are reversibly formed in the subsequent charge step. The reversible formation of the mixed Cu3P and amorphous phosphorus rather than CuP2 at full delithiation (2.0 V) in the following cycles is anticipated to improve the electrochemical performance of CuP2 anode because the metal-rich Cu3P is more conductive than CuP2, thereby enhancing particle conductivity along with conductive carbon network over extended cycling. From the DCP and ex situ XRD analyses discussed above, the lithiation and delithiation mechanism of CuP2 in lithium-ion cells can be summarized as follows: first discharge: CuP2 + 6Li+ + 6e− → 2Li3P + Cu

(0.57 V)

first charge: 2Li3P + Cu → Li 2CuP + P(amorphous) + 4Li+ + 4e−

(1.09 V)

Li 2CuP → (1/3)Cu3P + (2/3)P(amorphous) + 2Li+ + 2e− (1.25 V)

second discharge: (1/3)Cu3P + (2/3)P(amorphous) + 2Li+ + 2e− → Li 2CuP (0.89 V) Li 2CuP + P(amorphous) + 4Li+ + 4e− → 2Li3P + Cu

(0.78 V)

second charge: 2Li3P + Cu → Li 2CuP + P(amorphous) + 4Li+ + 4e− +

Li 2CuP → (1/3)Cu3P + (2/3)P(amorphous) + 2Li + 2e

(1.09 V) −

(1.25 V)

Figure 5. (a) Comparison of the cycle performance of the CuP2-based composites at current density of 200 mA g−1. All the cells were tested at 100 mA g−1 for the initial two cycles for activation. (b) Rate capability of pure CuP2 and CuP2/C composites and (c) high rate cyclability of the CuP2/C (20 wt %) composite at various current densities. The specific capacity was calculated using the total weight of the composite including carbon.

The cycle performance of the pure CuP2 and CuP2/C composite electrodes tested at 200 mA g−1 between 0 and 2.0 V (vs Li/Li+) is compared in Figure 5a. For activation, test cells were cycled at 100 mA g−1 for the first two cycles. The pure CuP2 electrode shows poor cycle performance with a gradual capacity drop, arising from the huge volume change (∼300%) in forming the fully lithiated phase (Li3P) upon cycling. After 50 cycles, a reversible capacity of ∼554 mA h g−1 is delivered, which is only ∼59% of its third cycle capacity. In contrast, regardless of the carbon content, the CuP2/C composite electrodes exhibit significantly improved cycling stability over 100 cycles. The obtained reversible capacities after 100 cycles were ∼817, ∼ 720, and ∼604 mA h g−1, respectively, for the samples with 10, 20, and 30 wt % carbon. The best cyclability is observed for the sample containing 20 wt % carbon, maintaining >95% of its capacity at the third cycle. Figure 5b compares the rate capability of the pure CuP2 and CuP2/C composite electrodes at various current rates from 100 to 1600 mA g−1. The pure CuP2 electrode exhibits the highest charge capacity of ∼1033 mA h g−1 at 100 mA g−1 among all the test electrodes. However, a reversible capacity of ∼604 mA h g−1 is obtained for pure CuP2 when the current density is increased to 1.6 A g−1, which is equivalent to only ∼58% of its capacity at 100 mA g−1. On the other hand, all the carbon

composite electrodes display much better rate performance than pure CuP2 as shown in Figure 5b. In particular, the delithiation capacities of the CuP2/C (20 wt %) composite electrode are measured to be ∼827, ∼ 772, ∼ 723, and ∼686 mA h g−1, respectively, at current densities of 100, 200, 400, and 800 mA g−1. This composite delivers the charge capacity of ∼637 mA h g−1 even at 1.6 A g−1, which indicates >77% capacity retention compared to its capacity at 100 mA g−1. In addition, a reversible capacity of ∼818 mA h g−1 can be resumed when the current density returned to 100 mA g−1 after high rate cycling tests, demonstrating significantly improved rate capability. In Figure 5c, the long-term cyclability of the CuP2/C (20 wt %) composite electrode is further obtained at higher current densities of 0.5 and 1.0 C rates (1 C = 800 mA g−1). It is surprising that a stable delithiation capacity of ∼640 mA h g−1 is delivered after 200 cycles tested at 0.5 C rate and a reversible capacity of ∼534 mA h g−1 is still maintained after D


Research Article


composite electrode (Figure 6b) maintains almost the same charge-transfer resistance from 10 cycles (∼6.3 Ω) to 100 cycles (∼6.2 Ω), which demonstrates that enhanced conductivity of the active materials could be achieved for the carbon composites. Furthermore, from the electrode surface morphologies of the pure CuP2 and CuP2/C (20 wt %) electrodes presented in Figure 7, it can be seen that conductive carbon network serves

250 cycles at 1.0 C rate, illustrating the excellent high rate cycle performance with even greater capacity than graphite. The dramatic enhancement in electrochemical performance of the CuP2/C (20 wt %) composite in terms of high reversible capacity and superior cyclability, as well as good rate capability, is mainly ascribed to the realization of the unique nanostructure composed of nanosized CuP2 particles well-embedded in a conductive carbon network that offers facile ionic/electronic transport paths as well as a durable volume buffer against large volume changes of the CuP2 active materials upon lithiation and delithiation. Moreover, the introduction of carbon could restrict the agglomeration of active particles during cycling by homogeneously dispersing them within the stable carbon matrix, leading to enhanced electrochemical reversibility and a good mechanical stability over cycling. Finally, the presence of local P−O−C bonding formed during HEMM might further prevent the detachment of the active particles from the composite electrode, maintaining a good particle connectivity during repeated cycling.21 Combined EIS and ex situ SEM studies were carried out to confirm the influence of the carbon matrix on the chargetransfer processes in the electrodes and the electrode integrity during cycling. Figure 6 and Figure S3 display the Nyquist plots

Figure 7. Changes in the electrode surface morphologies of the (a and b) pure CuP2 and (c and d) CuP2/C (20 wt %) composite electrodes after 10 and 100 cycles.

as an effective buffering medium against large volume expansion of the CuP2 active material during lithiation. Although the pure CuP2 electrode (Figure 7a,b) shows a surface rupturing with many macrocracks and the mechanical degradation after 100 cycles, the smooth surface is wellmaintained for the CuP2/C (20 wt %) composite electrode even after 100 cycles, as evident from Figure 7c,d, confirming that carbon matrix in the composite provides structural reinforcement, interfacial stability and improved electrochemical properties of the CuP2 active particles.

4. CONCLUSION Phosphorus-rich CuP2 and its carbon composites have been prepared by a simple, high-yield, environmentally benign HEMM process, and their electrochemical properties have been evaluated as anodes for lithium-ion batteries. The obtained phase-pure CuP2 and the CuP2/C composites have an average secondary particle size of a few micrometers with high tap densities (>1.1 g cm−3) greater than that of commercially available graphite anode materials. The CuP2/C (20 wt %) composite exhibits a high delithiation capacity of >836 mA h g−1 at 100 mA g−1 with a high initial CE of ∼83%. In addition, an excellent cycling stability over 100 cycles (>95% capacity retention) and enhanced rate performance up to 1.6 A g−1 (>77% of the capacity at 100 mA g−1) can be achieved for this composite. The simple introduction of conductive carbon matrix could not only provide the composite materials with enhanced conductivity and facile lithium-ion diffusion pathways but also act as a durable structure-reinforcing matrix that accommodates the large volume changes of the active CuP2 particles during cycling, maintaining enhanced mechanical integrity and structural flexibility. These superior electrochemical performances in combination with the facile and

Figure 6. Impedance spectra of (a) pure CuP2 and (b) CuP2/C (20 wt %) composite at various cycles.

for the pure CuP2 and CuP2/C (20 wt %) electrodes taken after various cycle numbers from 10 to 100 cycles. As shown in Figure 6a, a large increase in the charge-transfer resistance is observed for the pure CuP2 electrode over cycling. The obtained values from curve fitting (Table S1) using a simplified equivalent circuit (Figure S4) were ∼8.8 and ∼20.3 Ω, respectively, after 10 and 100 cycles. On the other hand, all the carbon composite electrodes exhibit much smaller semicircles than the pure CuP2 electrode even after 100 cycles (Figure 6b and Figure S3). Specifically, the CuP2/C (20 wt %) E


Research Article


(10) Hall, J. W.; Membreno, N.; Wu, J.; Celio, H.; Jones, R. A.; Stevenson, K. J. Low-Temperature Synthesis of Amorphous FeP2 and Its Use as Anodes for Li Ion Batteries. J. Am. Chem. Soc. 2012, 134, 5532−5535. (11) Ramireddy, T.; Xing, T.; Rahman, M. M.; Chen, Y.; Dutercq, Q.; Gunzelmann, D.; Glushenkov, A. M. Phosphorus-Carbon Nanocomposite Anodes for Lithium-Ion and Sodium-Ion Batteries. J. Mater. Chem. A 2015, 3, 5572−5584. (12) Sun, J.; Zheng, G.; Lee, H.-W.; Liu, N.; Wang, H.; Yao, H.; Yang, W.; Cui, Y. Formation of Stable Phosphorus−Carbon Bond for Enhanced Performance in Black Phosphorus Nanoparticle−Graphite Composite Battery Anodes. Nano Lett. 2014, 14, 4573−4580. (13) Bichat, M.-P.; Politova, T.; Pfeiffer, H.; Tancret, F.; Monconduit, L.; Pascal, J.-L.; Brousse, T.; Favier, F. Cu3P as Anode Material for Lithium Ion Battery: Powder Morphology and Electrochemical Performances. J. Power Sources 2004, 136, 80−87. (14) Stan, M. C.; Klöpsch, R.; Bhaskar, A.; Li, J.; Passerini, S.; Winter, M. Cu3P Binary Phosphide: Synthesis via a Wet Mechanochemical Method and Electrochemical Behavior as Negative Electrode Material for Lithium-Ion Batteries. Adv. Energy Mater. 2013, 3, 231−238. (15) Poli, F.; Wong, A.; Kshetrimayum, J. S.; Monconduit, L.; Letellier, M. In Situ NMR Insights into the Electrochemical Reaction of Cu3P Electrodes in Lithium Batteries. Chem. Mater. 2016, 28, 1787−1793. (16) Villevieille, C.; Robert, F.; Taberna, P. L.; Bazin, L.; Simon, P.; Monconduit, L. The Good Reactivity of Lithium with Nanostructured Copper Phosphide. J. Mater. Chem. 2008, 18, 5956−5960. (17) Pfeiffer, H.; Tancret, F.; Brousse, T. Synthesis, Characterization and Electrochemical Properties of Copper Phosphide (Cu3P) Thick Films Prepared by Solid-State Reaction at Low Temperature: a Probable Anode for Lithium Ion Batteries. Electrochim. Acta 2005, 50, 4763−4770. (18) Mauvernay, B.; Doublet, M. L.; Monconduit, L. Redox Mechanism in the Binary Transition Metal Phosphide Cu3P. J. Phys. Chem. Solids 2006, 67, 1252−1257. (19) Pfeiffer, H.; Tancret, F.; Bichat, M.-P.; Monconduit, L.; Favier, F.; Brousse, T. Air Stable Copper Phosphide (Cu3P): a Possible Negative Electrode Material for Lithium Batteries. Electrochem. Commun. 2004, 6, 263−267. (20) Wang, K.; Yang, J.; Xie, J.; Wang, B.; Wen, Z. Electrochemical Reactions of Lithium with CuP2 and Li1.75Cu1.25P2 Synthesized by Ballmilling. Electrochem. Commun. 2003, 5, 480−483. (21) Kim, S.-O.; Manthiram, A. The Facile Synthesis and Enhanced Sodium-Storage Performance of a Chemically Bonded CuP2/C Hybrid Anode. Chem. Commun. 2016, 52, 4337−4340. (22) Mao, J.; Fan, X.; Luo, C.; Wang, C. Building Self-Healing Alloy Architecture for Stable Sodium-Ion Battery Anodes: A Case Study of Tin Anode Materials. ACS Appl. Mater. Interfaces 2016, 8, 7147−7155. (23) Wu, N.; Yao, H.-R.; Yin, Y.-X.; Guo, Y.-G. Improving the Electrochemical Properties of the Red P Anode in Na-Ion Batteries via the Space Confinement of Carbon Nanopores. J. Mater. Chem. A 2015, 3, 24221−24225. (24) Suryanarayana, C.; Al-Aqeeli, N. Mechanically Alloyed Nanocomposites. Prog. Mater. Sci. 2013, 58, 383−502. (25) Kim, S.-O.; Manthiram, A. A Facile, Low-Cost Synthesis of High-Performance Silicon-Based Composite Anodes with High Tap Density for Lithium-Ion Batteries. J. Mater. Chem. A 2015, 3, 2399− 2406. (26) Kim, S.-O.; Manthiram, A. High-Performance Red P-Based P− TiP2−C Nanocomposite Anode for Lithium-Ion and Sodium-Ion Storage. Chem. Mater. 2016, 28, 5935−5942. (27) Gauthier, M.; Mazouzi, D.; Reyter, D.; Lestriez, B.; Moreau, P.; Guyomard, D.; Roue, L. A Low-Cost and High Performance BallMilled Si-Based Negative Electrode for High-Energy Li-Ion Batteries. Energy Environ. Sci. 2013, 6, 2145−2155. (28) Lin, D.; Lu, Z.; Hsu, P.-C.; Lee, H. R.; Liu, N.; Zhao, J.; Wang, H.; Liu, C.; Cui, Y. A High Tap Density Secondary Silicon Particle Anode Fabricated by Scalable Mechanical Pressing for Lithium-Ion Batteries. Energy Environ. Sci. 2015, 8, 2371−2376.

scalable synthesis route demonstrate that the CuP2/C composite offers great promise to be realized as a highperformance anode material for lithium-ion batteries.

■

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.7b02826. SEM mapping images of CuP2/C (20 wt %) composite, SEM/EDS analysis of pure CuP2 and CuP2/C (20 wt %) composite, impedance spectra of CuP2/C composites (10 and 30 wt % carbon contents), and comparison of the impedance values of pure CuP2 and CuP2/C composites obtained by curve fitting (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Sang-Ok Kim: 0000-0001-5628-9331 Arumugam Manthiram: 0000-0003-0237-9563 Present Address †

Center for Energy Convergence Research, Korea Institute of Science and Technology, Seoul 02792, Korea. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE-SC0005397.

■

REFERENCES

(1) Roy, P.; Srivastava, S. K. Nanostructured Anode Materials for Lithium Ion Batteries. J. Mater. Chem. A 2015, 3, 2454−2484. (2) Ji, L.; Lin, Z.; Alcoutlabi, M.; Zhang, X. Recent Developments in Nanostructured Anode Materials for Rechargeable Lithium-Ion Batteries. Energy Environ. Sci. 2011, 4, 2682−2699. (3) Boyanov, S.; Bernardi, J.; Gillot, F.; Dupont, L.; Womes, M.; Tarascon, J. M.; Monconduit, L.; Doublet, M. L. FeP: Another Attractive Anode for the Li-Ion Battery Enlisting a Reversible TwoStep Insertion/Conversion Process. Chem. Mater. 2006, 18, 3531− 3538. (4) Jiang, J.; Wang, C.; Liang, J.; Zuo, J.; Yang, Q. Synthesis of Nanorod-FeP@C Composites with Hysteretic Lithiation in LithiumIon Batteries. Dalton Trans. 2015, 44, 10297−10303. (5) Khatib, R.; Dalverny, A. L.; Saubanère, M.; Gaberscek, M.; Doublet, M. L. Origin of the Voltage Hysteresis in the CoP Conversion Material for Li-Ion Batteries. J. Phys. Chem. C 2013, 117, 837−849. (6) Pralong, V.; Souza, D. C. S.; Leung, K. T.; Nazar, L. F. Reversible Lithium Uptake by CoP3 at Low Potential: Role of the Anion. Electrochem. Commun. 2002, 4, 516−520. (7) Fullenwarth, J.; Darwiche, A.; Soares, A.; Donnadieu, B.; Monconduit, L. NiP3: a Promising Negative Electrode for Li- and Na-Ion Batteries. J. Mater. Chem. A 2014, 2, 2050−2059. (8) Gillot, F.; Boyanov, S.; Dupont, L.; Doublet, M. L.; Morcrette, M.; Monconduit, L.; Tarascon, J. M. Electrochemical Reactivity and Design of NiP2 Negative Electrodes for Secondary Li-Ion Batteries. Chem. Mater. 2005, 17, 6327−6337. (9) 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. F


Research Article

ACS Applied Materials & Interfaces (29) Allcorn, E.; Manthiram, A. High-Rate, High-Density FeSb-TiCC Nanocomposite Anodes for Lithium-Ion Batteries. J. Mater. Chem. A 2015, 3, 3891−3900. (30) Kim, S.-O.; Manthiram, A. High-Performance Zn−TiC−C Nanocomposite Alloy Anode with Exceptional Cycle Life for LithiumIon Batteries. ACS Appl. Mater. Interfaces 2015, 7, 14801−14807. (31) Kim, I. T.; Kim, S. O.; Manthiram, A. Effect of TiC Addition on SnSb-C Composite Anodes for Sodium-Ion Batteries. J. Power Sources 2014, 269, 848−854. (32) Shu, J.; Shui, M.; Huang, F.; Xu, D.; Ren, Y.; Hou, L.; Cui, J.; Xu, J. Surface Behaviors of Conductive Acetylene Black for LithiumIon Batteries at Extreme Working Temperatures. J. Phys. Chem. C 2011, 115, 6954−6960. (33) Fransson, L.; Eriksson, T.; Edström, K.; Gustafsson, T.; Thomas, J. O. Influence of Carbon Black and Binder on Li-Ion Batteries. J. Power Sources 2001, 101, 1−9.

G


Phosphorus-Rich CuP2 Embedded in ... - ACS Publications

Recommend Documents