Hydrothermal synthesis of nano bilayered v2o5 and electrochemical behavior in non–aqueous electrolytes lipf6 and naclo4

Journal of Science and Technology 55 (1B) (2017) 24–29 HYDROTHERMAL SYNTHESIS OF NANO BILAYERED V2O5 AND ELECTROCHEMICAL BEHAVIOR IN NON–AQUEOUS ELECTROLYTES LiPF6 AND NaClO4 Huynh Le Thanh Nguyen1, *, Nguyen Van Hoang2, Nguyen Thi Ngoc Dieu1, Huynh Bang Vy1, Le My Loan Phung1, 2, Tran Van Man2 1Applied Physical Chemistry Laboratory, Faculty of Chemistry, University of Science–VNUHCM, 227 Nguyen Van Cu, District 5, Ho Chi Minh City, Vietnam 2Department of Physical Chemistry, Faculty of Chemistry, University of Science–VNUHCM 227 Nguyen Van Cu, Ward 4, District 5, Ho Chi Minh City, Vietnam *Email: hltnguyen@hcmus.edu.vn Received: 30 December 2016; Accepted for publication: 2 March 2017 ABSTRACT This work aimed to prepare bilayered V2O5 by hydrothermal route from vanadium (III) chloride (VCl3). According to XRD results, bilayered V2O5 showed a large interlayer spacing around 11.3 Å. The electrochemical properties of bilayered V2O5 were carried out by cyclic voltammetry and charge–discharge testing in non–aqueous electrolytes LiPF6 and NaClO4. The curves charge–discharge showed that mechanism of insertion/extraction of Li+ ions and Na+ ions were occurred on a solution solid without the phase transition. Moreover, specific capacity for lithium and sodium intercalation of bilayered V2O5 were found out 250 mAh/g and 200 mAh/g, respectively. The kinetic of lithium’s and sodium’s insertion was evaluated by the electrochemical impedance spectroscopy (EIS). The EIS results exhibited a stabilization of charge transfer in both case and a slow kinetic of sodium’s diffusion compared to lithium’s case due to the large ionic radius of sodium. Keywords: electrochemical impedance spectroscopy, kinetics, lithium’s intercalation, sodium’s intercalation, bilayered V2O5. 1. INTRODUCTION In 21th century, rechargeable batteries are main key of modern technology in many applications from portable devices (smartphone, laptop) to large–scale (hydride electric vehicle–HEV, smart grid system) [1–3]. Among the rechargeable batteries, Li–ion battery (LIB) is outstanding member due to the highest gravimetric as well as volumetric capacity; and Sodium–ion batteries (SIBs) can have contribution to alternating LIBs in large–scale application. Li–ion and Na–ion batteries have the same configuration with an insertion/extraction reversible of Li+ ions and Na+ ions into electrode positive and negative during charge–discharge process [4, 5]. Huynh Le Thanh Nguyen, et al. 25 Bilayered V2O5 is a promising cathode material for both Li–ion and Na–ion batteries because of a large interlayer spacing around 10 Å [6, 7]. In this work, we investigate the insertion electrochemical of Li+ ion and Na+ ion into bilayered V2O5 in non–aqueous electrolyte. Moreover, a comparison of kinetics of lithium–sodium intercalation into nano crystalline V2O5 bilayered was carried out. The electrochemical impedance spectroscopy results exhibited the slow kinetics of sodium intercalation compared to lithium intercalation due to the large ionic radius of sodium. 2. MATERIALS AND METHODS Bilayered V2O5 were prepared by a hydrothermal route. A mixture of 1 mmol of VCl3 (Sigma–Aldrich, 97 %), 5 mL pyridine (Sigma–Aldrich) and 10 mL deionized water was stirred under vigorous at room temperature. After that, the precursor solution was heated at 180 °C in a teflon–lined autoclave for 12 hours. The precipitate was cooled to room temperature naturally, collected, and washed with deionized water and ethanol several times. The final products were obtained after drying at 120 °C in a vacuum oven overnight. Structures of these samples were identified by powder X–ray diffraction, using a X’Pert PRO MPD PANalytical diffractometer (at Center for Innovative Materials and Architectures, Ho Chi Minh City) with CoKα radiation (λ = 1.789 Å), 0.02° and 20 second pars step counting time. The diffraction pattern was collected for 2θ between 10° to 70°. The morphology and the distribution of grain size were determined by using a FE–SEM S4800 (Hitachi, Japan) at Institute of Chemical Technology–VAST. The electrochemical properties were measured in a Swagelok–type cell. The positive electrode was composed on material active (80 wt%), acetylene black (7.5 wt%), graphite (7.5 wt%) and teflon (5 wt%). The mixture was pressed directly on a stainless–steel grid under a pressure of 5 ton/cm2. Negative electrode was lithium or sodium metal and 1 M LiPF6/ethylene carbonate:dimethyl carbonate or 1 M NaClO4/propylene carbonate (2 % fluoroethylene carbonate) were used as electrolyte, respectively. Cells were assembled in a glove box under argon to avoid oxygen and water. The kinetic of insertion–extraction of lithium or sodium into bilayered V2O5 were investigated by using electrochemical impedance spectroscopy. Impedance measurements were performed in the frequency range from 106 Hz to 5×10–3 Hz. The excitation signal was 10 mV peak to peak. Electrochemical studies were carried out by using VMP3 apparatus (BioLogic–France). All electrochemical characterizations were implemented at Faculty of Chemistry, University of Science–VNUHCM. 3. RESULTS AND DISCUSSION 3.1. Structure and morphology The bilayered V2O5, called V2O5.nH2O xerogel, is a stack of long ribbon like slabs which are made up of octahedral [VO6] stacked along c–axis, as shown in Figure 1a with a distance inter–layer of 11.5 Å [8–10]. The XRD pattern of bilayered V2O5 (Figure 1b) showed the typical (00l) refection peaks, which are consistent with those of the layered structure of V2O5.nH2O (JCPDF: 40–1296). According to XRD pattern, the distance interlayer was determined to 11.7 Å. Due to the hydrothermal reaction, the peaks in XRD pattern had quite large. It is considered that the sample was crystallized in small particle sizes. According to the Debye–Scherrer equation (1), the average size of particles was calculated from the full width of half maximum (FWHM) of diffraction peaks: Hy 26 wh wa is t fas dif dis aro 3.2 bil wh int (ex 1 M dis drothermal s ere dhkl is th velength of he diffractio t kinetic of fusion. As can b tribution, an und 1 μm. . Electroche During ch ayered V2O5 ere A+ may ercalation ( traction, cha Figure 3a LiPF6/EC charge curv ynthesis of e average si CoKα X–ray n angle. Th intercalatio e seen in d the particl Figure 1. mical prop arge–discha occur follow represent a insertion, d rge). Interca showed the :DMC (1:1) es showed a nano bilayer ze, k is the radiation ( e size reache n of lithiu Figure 2, e size fell in Structure of b Figure 2. S erties rge process ing electro V2O5 monovalent ischarge), w lation and d typical cha solution at w totally reve ed V2O5 and ࢊࢎ࢑࢒ ൌ ࢼࢉ constant dep 1.789 Å), β d around 20 m and sodi the sample to the micro ilayered V2O EM images o , the inserti chemical rea + xA+ + xe– cation (Li+ a hile the b eintercalatio rge–discharg indow pot rsible interc electrochem ࢑ࣅ ࢕࢙ࣂ ending on th is the FWHM nm. The na um ion due bilayered V metric dime 5 and XRD p f bilayered V on/extraction ction: ↔ AxV2O5 nd Na+). He ackward rea n proceed re e curves of ential 1.5–4. alation of L ical behavio e crystallite of the mos nosize of pa to shorten 2O5 had a nsion scale. attern of samp 2O5. of Li+ ion re, the forw ction is ter versibly in o bilayered V 2 V (vs. Li+ i+ ions. In t i r in non–aq shape (0.9) t intense pe rticles will ing the pat homogeno The particle le. s and Na+ ard reaction med deinte pposite dire 2O5 in non– /Li). All the he 1st cycle, ueous (1) , λ is the ak, and θ suggest a hway of us grain size was ions into is called rcalation ctions. aqueous charge– the host cou Mo un per mA 1 M irr 1st str wi ins int 4b 3.3 im fre ld insert 1 reover, the complicated formance w h/g. Figure 3 Figure 4a NaClO4/P eversible ins reduction b uctural of b th an electro ertion of so eraction of N ; after thirty Figure 4. ( . Kinetic of Kinetics o pedance sp quency rang .5 Li+ ions curves repr insertion as presented . (a) Typical showed the C (2 % FEC ertion of Na ut only 0.9 ilayered V2O chemically dium ions. a+ ions and cycles, a spe a) Typical cha lithium’s an f alkaline io ectroscopy e 105 Hz , correspond esent a low of Li+ ions in Figure 3 charge–discha 1 M typical cha ) solution a + ions were o Na+ ions co 5 and α–V2 formed phas All the curv bilayered st cific capacit rge–discharg NaC d sodium’s n’s transpor method. Th to 5×10–3 H ing to a m polarization with a m b; after fifte rge curves an LiPF6/EC:D rge–discharg t window p bserved, bil uld extract O5. In α–V2 e α’–NaV2O es showed ructure. The y reduced to e curves and ( lO4 1 M/PC ( intercalati t into bilaye e impedan z at a vari aximum sp as well as echanism en cycles, a d (b) cycling MC (1:1). e curves of otential 1–4 ayered V2O in oxidation O5 case, the 5 [11]. In 2 a large pola cycling perf 100 mAh/g b) cycling pe 2 % FEC). on red V2O5 wa ce measure ous content Huynh Le ecific capa a simply fo of solution specific cap performance bilayered V V (vs. Na+ 5 could inser . This result sodium's in nd cycle, we rization tha ormance wa . rformance of s determine ments were of alkaline Thanh Nguy city of 230 rm that ind solid. The acity reduce of bilayered V 2O5 in non– /Na). In 1st t 1.35 Na+ io exhibited a sertion acco observe a r t suggested s presented bilayered V2O d by electro performed ion. The en, et al. 27 mAh/g. icates an cycling d to 150 2O5 in aqueous cycle, an ns in the relation mpanied eversible a strong in Figure 5 in chemical in the diffusion Hy 28 co [12 wh (0. rel in fre res rea an dif 0,1 co (Fi lith 0.0 dis we drothermal s efficients of ]: ere, VM is t 785 cm2); │ ation betwee For lithiu the high–m quency f* = istance of ch l axis demo gle was incre fusion allow and DLi = 8 efficients in In case o gure 6). How ium’s case, 2 Hz). It co charge proc re found DN ynthesis of alkaline ion he molar vo dE/dx│ is t n ZReal and ω m’s intercal edium freq 63 Hz. An u arge transfe nstrated the asing which ed to calcul .9×10–9 cm2 α–V2O5 and F F f sodium’s ever, the “ and the Wa uld be expla ess and a la a = 9.5×10–1 nano bilayer D were ca ࡰࡸ࢏/ࡺ lume of host he slope at f –1/2 in the W ation, the di uency corre nchanged ch r”. The low Warburg im belonged to ate the lithi /s for xLi = 0 bronzes MxV igure 5. AC i igure 6. AC i intercalatio quasi–resista rburg region ined by the rger ionic r 1 cm2/s for x ed V2O5 and lculated from ࢇ ൌ ቀ ࢂࡹ√૛ࡲࡿ ൈ (VM = 54.5 ixed x and d arburg imp agram impe sponded to aracteristic frequency r pedance and the finite d um diffusion .4. These va 2O5. mpedance di mpedance dia n, the diag nce of char in sodium passivation adius of so Na = 0.1 and electrochem region Wa ࢊࡱ ࢊ࢞ ൈ ૚ ࡭࣓ቁ ૛ cm3/mol); S etermined b edance. dance presen the charg frequency p egion, a stra at lower fre iffusion proc coefficient lues were co agrams for Li grams for Na ram impeda ge transfer” ’s case was and evolutio dium ion. T DNa = 1.2×1 ical behavio rburg by fo is the active y curve C/6 ted three re e transfer w roposed a sta ight line 45° quencies (f ess (Figure s: DLi = 1.3 herent with 0.1V2O5. 0.1V2O5. nce exhibit in sodium’s found at low n of sodium he sodium d 0–11 cm2/s fo i r in non–aq llowing equ surface of 0, Aω is the gions. A sem ith a char bilization o (1–0.1 Hz) < 10–3 Hz) t 5). The sem ×10–9 cm2/s the lithium ed the sam case was la er frequenc ’s surface d iffusion co r xNa = 0.4. ueous ation (2) (2) electrode slope of i–circle acteristic f “quasi– from the he phase i–infinite for xLi = diffusion e model rger than ies (0.4– uring the efficients Huynh Le Thanh Nguyen, et al. 29 4. CONCLUSIONS In summary, we had synthetized nano–crystalline bilayered V2O5 by hydrothermal rout from a precursor of VCl3. The XRD pattern of bilayered V2O5 showed the typical (00l) with an interlayer spacing of 11.7 Å. Bilayered V2O5 could insert reversiblely 1.5 ion Li+ (~220 mAh/g); while a stability of sodium’s intercalation occurred at 0.8 ion, corresponding to a specific capacity of 120 mAh/g. The sodium diffusion coefficients were found around 10–11 cm2/s, This value is lower 100 times than the lithium diffusion coefficients (~10–9 cm2/s) due to a larger ionic radius of sodium ion. Acknowledgements. 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