SnO2 Based Materials and Their Energy Storage Studies - ACS

Subscriber access provided by TUFTS UNIV

Article

SnO2 based Materials and their Energy Storage Studies Mogalahalli Venkatashamy Reddy, Tran Thuy Linh, Dang Thu Hien, and Bobba Venkateshwara Rao Chowdari ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b00445 • Publication Date (Web): 26 Sep 2016 Downloaded from http://pubs.acs.org on October 2, 2016

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 free 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 accessible to all readers and 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.

ACS Sustainable Chemistry & Engineering 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 39

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 Sustainable Chemistry & Engineering

SnO2 based Materials and their Energy Storage Studies Mogalahalli Venkatashamy Reddy1, 2*, Tran Thuy Linh2,3,4, Dang Thu Hien2,3,5, Bobba Venkteshwara Rao Chowdari2 1

Department of Materials Science and Engineering, 9 Engineering Drive 1, National University

of Singapore, Singapore 117575 2

Department of Physics, 2 Science drive 3, National University of Singapore 117542

3

NUS High School of Mathematics and Science, 20 Clementi Avenue 1, Singapore 129957

4

Department of Pharmacy, 18 Science Drive 4, Singapore 117543

5

NUS School of Business, 15 Kent Ridge Drive, National University of Singapore 119245

Corresponding Author: *[email protected]; [email protected]; [email protected]; Telephone number: +65-65162607.

ACS Paragon Plus Environment


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

ABSTRACT We attempted to prepare SnO2 based oxide materials by molten salt method (MSM) using KCl at 850 °C and 1050 °C and 0.5M KCl:0.5MNaCl at 650°C for 3h in air. The compounds were characterized by Rietveld refined X-Ray Diffraction (XRD), X-ray photo electron spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area methods. XRD studies show tetragonal SnO2 type structure. Compounds exhibited surface areas ranging from 0.78 to 5.68 m2 g-1. The Electrochemical (anodic) behavior of samples prepared at 850 °C and 650 °C were examined by galvanostatic cycling (GC) and cyclic voltammetry (CV) vs. Li-metal in the voltage range 0.005-1.0V or 0.005-3.0V vs Li. All compounds display main cathodic peak at ∼0.25V and anodic peak at ∼0.5V based on the CV studies, which are characteristic cathodic and anodic peaks of SnO2. Anodic properties showed a reversible capacity values in the range 639 – 714 mAhg-1 in the voltage range, 0.005-1.0 V vs. Li. Tin oxides made from Co-sulfate and SnCl2 generally displayed a high storage capacity with good capacity retention. When we cycled to higher cut-off voltage (0.005-3.0V) capacity fading was noted in all compounds due to huge volume variation conversion reaction of respective Snoxides.

Keywords: M-SnO2 (M=Co,In); Molten salt synthesis; Characterization; Energy Storage

INTRODUCTION The incessant demand for portable telecommunication devices, computers and hybrid vehicles has gestated the growing demand for a portable source of electrical energy. Li-ion batteries (LIBs) surpasses all the rechargeable batteries currently available in the market, with

2 ACS Paragon Plus Environment

Page 2 of 39

Page 3 of 39

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


its high energy density per weight and volume (which allows the storage of high amounts of electrical energy within a small cell with light weight), the reduced impact on the environment, and the lower cost incurred in production. Also, the lifespan of LIBs is not affected by the partial charging as they do not suffer from memory effect, making them even more appealing to consumers. Thus, as of now, they are considered to be the most suitable DC power sources. To further maximize the potential of LIBs, the following preferred properties of anode materials: environmental-friendliness, low cost, insolubility in electrolyte solvents, inertia to substance of the electrolytes, low voltage profile vs. Li-metal, large reversible capacity with little capacity loss, and good Li-ion kinetics to enable current taking up - need to be considered. Graphite, operating on the basis of reversible Li-intercalation/de-intercalation reaction1, is employed as the current anode material in LIBs. However, it has a low theoretical capacity (≤372 mAhg-1) with the capacity fading at high current rate as Li metal lays on the graphite anode, hence may not be suitable for use in high energy applications. This motivates more researches on alternative materials meeting the desired characteristics of ideal anodes. Recently, tertiary tin oxides are growing as promising anode replacements2, 3. These materials operate based on alloying-de-alloying reaction (with cycling voltage ≤1V) and have a high capacity (~500-650 mAhg-1) with low charge/discharge potential vs. Li. However, Sn poses the problem of large volume variation (~300%), which leads to the strong internal mechanical stresses and particles cracking during electrochemical cycling3. This problem causes the electrical contact with the current collector to be lost, further worsening the capacity fading. Several strategies have been worked out to improve the capacity retention, such as reducing the particle size of the active material to nano-size, choosing a proper starting crystal structure, morphology and restricting the voltage range of cycling vs. Li., adopting different matrix



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

Page 4 of 39

elements, using spectator matrix elements, adopting voltage ranges and other factors, which have been thoroughly discussed in the recent review by Reddy et al.3 A large number of Sn-based ternary oxides of various crystals have also been further researched on and tested3, with positive results showing that the starting crystal structure, the nature and amount of the matrix element, the morphology and particle-size (micron-size or nano-size) are factors of significance for the capacity reversibility because of the alloying–de-alloying reaction of Sn-metal, and the long-term Li-cycling stability at various current (C)-rates. Thus, compounds containing Sn- oxides could give stable capacities. In addition, the morphology of well-crystalline, nano-size agglomeration ensures good long-term Li-cyclability. High surface area and short diffusion lengths for the Li-ion diffusion of the nano-size particles reduce the volume variations during Li-cycling with the help of the matrix element. Furthermore, subsequent electrochemical reactions and cycling involve the alloying–de-alloying reaction of Sn-metal. Sn containing matrix oxides such as (M1/2Sb1/2Sn)O4 (M= V, Fe, In)4, 5, MSnO3 (M= Ca, Sr, Ba)6-8, M2SnO4 (M=Mg, Mn, Co, Zn)9, 10, K2(M, Sn)8O16 (M=Li, Mg, Fe, Mn, Co, In)11, 12

and Y2Sn2O713 have been studied. Furthermore, in the past few years, the various

nanostructured composite oxides SnO2-TiO214, SnO2-In2O315 and MoO3.SnO217 were explored also attempts on Sb, Al, Fe, Sn, Cu, Ni, Mo and Zn doped SnO2 have been studied for use as anode materials16-23. The expected theoretical capacities in mAh/g during first charge cycle are Sn: 993, SnO:875, SnO2: 782 mAhg-1 cycled in the voltage range, V= 0.005-1.0V and SnO:1273, SnO2:1493 mAhg-1 cycled in the voltage range, V=0.005-3.0V. The proposed reaction mechanisms of SnO2 and their composite oxides (V= 0.005-1.0V, & 3.0V)3. SnO2+4Li+4e- Sn+2Li2O

(1)

Sn + 4.4Li+ +4.4e- ↔ Li4.4Sn

(V= 0.005-1.0V)


(2)

Page 5 of 39

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


Sn + 4Li2O ↔ SnO SnO2 + 4Li + 4e- (V= 0.005-3.0V) (3) Co0.33Sn0.67O2 + 4Li+4e- 0.33Co+0.67Sn+ 2Li2O (4) 0.67Sn + 4.4Li+ +4.4e- ↔ 0.67Li4.4Sn (V=0.005-1.0 V) (5) Co or Sn + Li2O ↔ CoO or SnO +2 Li +2e- (V=0.005-1.5 V) (6) CoO. SnO + Li2O ↔ Co0.33Sn0.67O2+2 Li+2e- (V=0.005-3.0 V) (7) In2O3 + 6Li+6e- 2In+ 3Li2O (8) 2In + 6Li+ +6e- ↔ 2Li3In (9) Co3O4 + 8Li+8e- LixCo3O4 3Co+ 4Li2O (9) To understand effect of molten salts on crystal structure, morphology and to study the Li-cyclability of Sn based composite oxides, the materials have been prepared by molten salt method (MSM). MSM method has been applied to prepare various other simple oxides

24, 25

to

generate a cost-effective, defect-free material with good electrochemical performance26-29. In this paper, we attempted to synthesize the Sn based composite oxides using KCl at 850 0C, 1050°C in air and 0.5MKCl:0.5M NaCl at 650 0C molten salt, and study their energy storage properties. EXPERIMENTAL SECTION Sn-based materials were prepared using molten salt method by mixing KCl, Cohydroxide (Aldrich)/ In-acetate (Aldrich), and SnCl2.2H2O in the molar ratio of 10:2:6 in an alumina crucible. The mixture was then heated at 8500C for 3h and 1050°C for 12h in air in a box furnace (Carbolyte, UK) (heating and cooling rate: 30C min-1). After cooling down to an ambient temperature, it was washed with distilled water to remove excess soluble KCl salt and filtered. The schematic diagram is shown in Fig.1. The filtered powder was then dried in an air oven at 70°C overnight, 4-5g of final product was obtained and stored in desiccator for further



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

characterization. To understand the eﬀect of preparation temperature and molten salt, compounds were prepared using 0.5MNaCl:0.5MKCl salt at 6500C, for 3h in air.

Figure 1: Graphic illustration of preparation of Sn- based compounds by Molten Salt Method

The composite electrodes for electrochemical studies were fabricated by mixing active material (prepared only at 850°C and 650°C), super P carbon black (MMM, Ensaco) (electronically conducting additive) and polyvinylindene fluoride (PVDF) copolymer binder (Kynar2801) in the mass ratio of 70:15:15. N-Methyl-pyrrolidinone (NMP) acted as organic solvent to form homogenous slurry, which was coated onto an etched Cu-foil (Alpha Industries Co.Ltd., Japan) using doctor blade technique to form a thick layer of ~ 15 µm. The foil was then dried at 70oC for 12h in an air oven to evaporate the NMP. The film was pressed in between stainless steel twin-rollers to ensure better electrical contact between the electrode material and the Cu-substrate, and cut into circular discs (16mm diameter, 2.0 cm2)30. The discs were vacuum-dried at 70oC for 12 h in a vacuum oven and transferred to the Ar-filled glove box (MBraun, Germany) for the cell assembly. The atmosphere in the glove box was maintained at

SnO2 Based Materials and Their Energy Storage Studies - ACS

Recommend Documents