C Composites as

Subscriber access provided by The University of Texas at El Paso (UTEP)

Article

Aerosol Assisted Synthesis of Spherical Sb/C Composites as Advanced Anodes for Lithium Ion and Sodium Ion Batteries Xiaoyan Liu, Yue Tian, Xiaoqing Cao, Xinru Li, Zaiyuan Le, Dieqing Zhang, Xianyang Li, Ping Nie, and Hexing Li ACS Appl. Energy Mater., Just Accepted Manuscript • Publication Date (Web): 16 Oct 2018 Downloaded from http://pubs.acs.org on October 16, 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 27 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

Aerosol Assisted Synthesis of Spherical Sb/C Composites as Advanced Anodes for Lithium Ion and Sodium Ion Batteries Xiaoyan Liua, Yue Tiana, Xiaoqing Caoa, Xinru Lib, Zaiyuan Leb, Dieqing Zhanga, Xianyang Lib, Ping Niec*, and Hexing Lia* a

Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of

Rare Earth Functional Materials, Department of Chemistry, Shanghai Normal University, Shanghai 200234, China. b

Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095, United States.

c

Key Laboratory of Preparation and Applications of Environmental Friendly Material of the Ministry of Education & College of Chemistry, Jilin Normal University, Changchun 130103, China.

Corresponding Author: Ping Nie (*Email: [email protected]) Hexing Li (*Email: [email protected])

Abstract: Metallic antimony (Sb) has been considered to be one of the most promising anode materials for both lithium-ion and sodium-ion batteries. However, Sb anode still suffers from the issues of poor conductivity and large volume expansion during charge-discharge process, which severely limited its applications. Herein, Sb/C composite is designed and fabricated with the assistance of aerosol spray technique and subsequent pyrolysis. Nanosized Sb particles are uniformly dispersed in the carbon matrix, suggesting improved conductivity and robust 1

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

structure. A high initial specific capacity of 641 mAh g-1 is achieved at a current density of 100 mA g-1 and 502 mAh g-1 is remained after 150 cycles in sodium batteries. When used as anodes for lithium batteries, Sb/C exhibits an initial capacity of 917 mAh g-1 and 590 mAh g-1 is remained after 80 cycles at a current density of 100 mA g-1. Such excellent electrochemical performance of Sb/C can be attributed to the elaborately organized nanostructure, which can effectively accommodate the volume change and suppress the aggregation of Sb nanoparticles during cycling for batteries application.

TOC

Key words: Antimony, Robust nanostructure, Anode material, Sodium-ion batteries, Lithium-ion batteries

2


Page 2 of 27

Page 3 of 27 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. Introduction Low cost and scalable energy storage system are crucially demanded due to the utilization and deployment of renewable energy.1 Lithium-ion batteries (LIBs) are considered as the most successful commercial rechargeable batteries, which have been widely applied as reliable energy storage devices for portable electronics.2 However, the state-of-the-art of LIBs with graphite anode can only offer specific energy of 160 Wh kg-1 and energy density of 600 Wh L-1, which are approaching their theoretical limits and cannot satisfy the requirements of electric vehicles and smart grids.3-5 Therefore, developing high-capacity anodes has been considered as a promising approach towards next-generation LIBs with improved gravimetric/volumetric energy.6 Furthermore, sodium-ion batteries (SIBs) have been intensively studied as potential alternatives to LIBs owning to the abundance of sodium sources compared to lithium (almost 1000 times higher than lithium in earth),7-8 which is more attractive for low cost and large-scale energy storage. Similarly, hard carbon is the widely investigated anode material for SIBs. However, these materials provide a lower capacity of 300 mAh g-1 and slower kinetics during charge-discharge process, leading to limited capacity and energy density.9-10 Therefore, exploring novel anode materials with high capacity seems desirable for both lithium-ion and sodium-ion batteries.11-12 In the past decades, Sb has emerged as a promising candidate due to its high theoretical capacity of 660 mAh g-1 upon full lithiation or sodiation and suitable working potential (about 0.8-0.9 V vs Li+/Li and 0.5-0.8 V vs Na+/Na).13-15 3



Nevertheless, its inherent low conductivity and large volume expansion (>300%) lead to poor electron transport and pulverization of electrode, which results in rapid capacity decay and limited lifespan.16-17 Great efforts have been devoted to address the above problems in the previous investigations, among which designing nanostructured Sb/carbon composites is a promising strategy due to the superior conductivity and buffer effect of carbon matrix, which could dramatically improve the electron/ion conductivity, accommodate the volume expansion and prevent the Sb nanoparticles from aggregation.12, 18 Hence, various strategies have been explored to fabricate homogenous Sb/C composite electrode materials, such as sol-gel19, solvothermal,20-21 ball milling,22 electrospinning23 and so on.24 For instance, Cao and co-workers prepared Sb-C nanofibers via an electrospinning process with additional calcination. The Sb-C fiber exhibited an improved capacity of 631 mAh g-1 at C/15 and good cycling stability with 90% capacity retention after 400 cycles at C/3.12 Yu group synthesized two dimensional Sb/C material through the “top-down” strategy, which presented enhanced electrochemical performance as an anode material for sodium batteries.13 Although these Sb/C materials with specific nanostructures have achieved improved capacity and electrochemical stability in the previous research, most of them were synthesized under specified laboratory condition, which may not be suitable for large scale production and limit their commercial application. Thus, designing appropriate route to synthesize scalable Sb/C materials with favorable nanostructures is still meaningful. Recently, aerosol spray technique has been considered as an attractive, low cost and 4


Page 4 of 27

Page 5 of 27 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


scalable route to fabrication nanostructured materials, which has been widely used for energy storage.25-27 Until now, the synthesis of Sb/C composites via aerosol spray technique is rarely reported.28 In 2015, Cao and colleagues reported the Sb@C microspheres prepared via aerosol spray drying with SbCl3 and polyacrylonitrile as precursor.29 However, the Sb content was as low as 40.8%, which severely decreased the capacity and energy density of the whole electrode. Besides, the dissolved SbCl3 tends to aggregate during the aerosol spray process, leading to larger particles with the increasing Sb contents, which may result in electrode pulverization due to the serious volume expansion.30 Therefore, fabricating homogenous Sb/C composites with smaller Sb nanoparticles well encapsulated and high Sb content is favorable for improving its cycling stability and energy density for both LIBs and SIBs. Herein, we synthesized a Sb/C nanospheres as anode materials for both LIBs and SIBs with the assistance of aerosol spray technique. The commercial Sb2O5 colloidal was selected as Sb source due to its superior dispersibility and nanosized diameter around 10 nm. Polyethylene oxide was used as the precursor of carbon matrix. After subsequent calcination, homogenous Sb/C composite with a high Sb content of 74 wt.% were obtained, in which Sb nanoparticles were well embedded by the conductive carbon matrix, implying enhanced conductivity and effective buffer for the volume expansion during discharging process. As anticipated, the Sb/C composites exhibited remarkable rate performance and prolonged lifespan in both LIBs and SIBs. 2. Experimental Section

2.1 Material synthesis 5



Page 6 of 27

The Sb/C nanosphere was prepared via an aerosol spray process. Typically, 3 g PEG 2000 (Sigma-Aldrich) was dissolved in 20 mL methanol and then 15 g colloidal Sb2O5 (SUNCOLLOID®AMT-330S, Nissan Chemicals Inc.) was added to get a homogenous solution. This precursor solution was atomized using nitrogen as carrier gas with the heating zone temperature of 450 °C. The as-collected particles were further treated at 450 °C for 3 h with a ramping rate of 3.5 °C min-1 under 5% H2-95% Ar atmosphere. The obtained product was marked as Sb/C. As comparison, the control sample was synthesized via mechanical mix and solvent evaporation method. In detail, 3 g PEG 2000 was dissolved in 20 mL methanol and then 15 g colloidal Sb2O5 was added. The above mixture was stirred under 60 °C to evaporate the methanol. Then white power was collected and further calcined under the same condition to Sb/C. The obtained control sample was denoted as Sb/C-mix.

2.2 Material characterization Powder X-ray diffraction (XRD) was conducted on a BRUKER D8 ADVANCE X-ray powder diffractometer using Cu-Kα radiation (λ = 1.54 Å). Thermogravimetric analysis (TGA) was conducted on SDT Q600 instrument at a ramping rate of 10 °C min-1 in air. The morphology and microstructure of the samples were investigated by scanning electron microscopy (SEM, HITACHI, S-4800) and transmission electron microscopy (TEM, JEOL JEM-2100). The Raman spectrum was measured by a Renishaw Invia Raman microscope with a 532 nm laser. The specific surface area and pore

volume

were

calculated

by

Brunauer-Emmett-Teller

(BET)

and

Barrett-Joyner-Halenda (BJH) models on desorption branches (Micromeritics TriStar 6


Page 7 of 27 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


II 3020 instrument).

2.3 Electrochemical measurement The electrochemical performance was evaluated using a CR2032 coin cell (MTI Corporation) assembled in an Ar-filled glove box. The anode was prepared by mixing Sb/C composite (70 wt%), acetylene black (15 wt%) and sodium alginate (SA) (15 wt%) in DI water. The slurry was uniformly spread onto a copper foil and dried at 80 °C for 10 h under vacuum condition. Then, the anode was punched into pellets with a diameter of 14 mm. The typical active material loading is 1.0 mg cm-2. The electrolyte used in the sodium ion batteries was 1 M sodium perchlorate (NaClO4)

in

a

propylene carbonate

solvent

mixture

of

ethylene

carbonate

(EC)

and

(PC) with a volume ratio of 1:1, including 5 vol%

fluoroethylene carbonate (FEC) as an additive. A glass fiber membrane (GF/D, Whatman) was used as the separator and sodium metal was used as counter and reference electrode. Similarly, the electrolyte used in the lithium ion batteries was 1 M lithium hexafluorophosphate (LiPF6) in a solvent mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) with a volume ratio of 1:1, including 5 vol% fluoroethylene carbonate (FEC) as an additive. A Celgard 2400 membrane was used as the separator and lithium metal was used as counter and reference electrode. The galvanostatic charge/discharge measurements for half cells were carried out on battery test systems (CT2001A, LAND) at various current densities with a cut-off potential ranges of 0.01-2.5 V for lithium and 0.01-2.0 V for sodium ion batteries. Cyclic

voltammetry

was

conducted

using

a

7


potentiostatic/galvanostatic


electrochemical workstation (Bio-Logic SAS, VSP-150 or VSP-300, Claix, France) with a scan rate of 0.01 mV S-1 from 0.01-2 V. Electrochemical impedance spectrum (EIS) measurements were performed on an electrochemical workstation (CHI 760E) in the frequency range from 100 KHz to 100 mHz. 3.

Results and discussion As illustrated in Figure 1, the Sb/C composite was synthesized via the aerosol spray

process and subsequent calcination. We started with the colloidal precursor containing commercial Sb2O5 colloids and PEG/methanol solution. The aerosol spray process generated droplets by the atomizer (Figure 1b), which were constructed by the precursor. In the following drying zone, the nanostructured sphere was generated after the evaporation of methanol. Then, the aerosol product was further carbonized and sintered at 450 °C for 3h under 5% H2/Ar atmosphere, leading to the formation of robust Sb/C nanospheres with Sb nanoparticles embedded.

8


Page 8 of 27

Page 9 of 27 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 1 The scheme of the synthesis of Sb/C sample via an aerosol spray process (a). Detailed illustration of Sb/C nanosphere prepared via aerosol spray process and further calcination (b).

The morphologic characteristics of Sb/C and Sb/C-Mix were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). As exhibited in Figure S1, the spherical product could be obtained after high-temperature aerosol spray process, which is denoted as Sb/C-Pre, presenting 300-1000 nm spheres with smooth surface. After further sintering, the nanostructured Sb/C sphere is well maintained, while the surface becomes rough due to the carbonization and decomposition of Sb/C-Pre. Furthermore, microstructures are demonstrated by TEM (Figure 2c), which confirmed that nanosized Sb particles are 9



well encapsulated in the carbon matrix, resulting increased conductivity and stability of anode material. Moreover, the uniformly dispersed Sb nanoparticles could be well limited and prevented from aggregation by the carbon buffer. It is observed that Sb nanoparticles in Sb/C are crystalline with diameter ranging from 10-20 nm and well agree with the Sb2O5 nanoparticles in precursor, indicating that Sb2O5 nanoparticles are effectively separated by PEG via aerosol spraying. The lattice space could be detected as 0.31 nm, which matches well with the (012) plane of Sb.19 As comparison, the Sb/C-Mix displays random structure (Figure S2), in which Sb bulks were partially coated by carbon layer. Moreover, the energy dispersive spectroscopy (EDS) mapping images of Sb and C exhibit that Sb nanoparticles are uniformly distributed within the carbon matrix.

10


Page 10 of 27

Page 11 of 27 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 2 Morphologic characteristics of Sb/C microsphere. SEM (a and b) and TEM (c and d) images of Sb/C microsphere.

The phase and crystal structure of Sb/C-Pre, Sb/C and Sb/C-Mix were characterized by X-ray diffraction (XRD) analysis. The XRD pattern of Sb/C-Pre (Figure 3a) shows that the obtained aerosol product contains Sb6O13 (JCPDS No. 33-0111) after the pre-pyrolysis. After further carbonization and reduction, the XRD pattern of Sb/C (Figure 3b) exhibits the typical peaks of metal Sb (JCPDS No. 35-0732), indicating the presence of Sb nanoparticles. Meanwhile, a broaden peak around 2θ = 23° can be observed, which is assigned to the carbon layer coated on Sb. 11



The distinct peaks of Sb are also displayed by Sb/C-Mix. Meanwhile, weaker carbon peak could be observed owning to the mixed structure of Sb and carbon. The Sb contents of Sb/C and Sb/C-Mix are determined by thermogravimetric analysis (TGA) in air, as shown in Figure 3c. The slight weight loss before 200 °C is attributed to the evaporation of water adhered on the surface of the samples. The following weight increase over 260 °C can be assigned to the oxidation of Sb to Sb2O4.12 Meanwhile, the carbon combustion brings a sharp weight decrease over 550 °C and then the sample reaches a stable state over 660 °C. Therefore, the total Sb contents of Sb/C and Sb/C-Mix are calculated to be 74.0 wt% and 72.0 wt%, respectively.31-32 The Raman spectra of Sb/C and Sb/C-Mix are presented in Figure 3d. Broad peaks at 1350 cm-1 and 1597 cm-1 are observed in the both samples, corresponding to the typical D and G bands of carbon materials. Besides, the intensity ratio of ID/IG are 0.95 and 0.99 of Sb/C and Sb/C-Mix, respectively, indicating the presence of partially graphitic carbon. The Brunauer-Emmett-Teller (BET) measurement was carried out to evaluate the porosity of Sb/C and Sb/C-Mix. There is an obvious hysteresis loop in N2 adsorption-desorption isotherm (Figure S4a), indicating the mesoporous structure of Sb/C. The surface area of Sb/C is 169.5 m2 g-1, which is higher than that of Sb/C-Mix (48.5 m2 g-1). As the BJH pore size distribution exhibits (Figure S4b), the mesopores are mainly centered around 5 nm. This porous structure can effectively buffer the volume expansion during charge discharge process.

12


Page 12 of 27

Page 13 of 27 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 The XRD patterns of Sb/C-Pre, Sb/C and Sb/C-Mix (a and b). The typical TGA curves and Raman spectra of Sb/C and Sb/C-Mix (c and d).

The electrochemical performance of Sb/C and Sb/C-Mix is investigated in half cells as anodes for sodium ion batteries. Figure 4a exhibits the cyclic voltammogram (CV) curves of Sb/C electrode for the initial four cycles at a scan rate of 0.1 mV s-1 between 0.01-2 V (Vs. Na+/Na). A pronounced peak around 0.21 V is detected during the first cathodic scan, which is related to the alloying reaction of Sb and sodium. The second cathodic process shows three reduction peaks at about 0.69, 0.51 and 0.30 V, respectively, which are assigned to the multi-step alloying reactions of Sb and sodium to form NaxSb (x

C Composites as

Recommend Documents