锂电池

Nickel foam-supported porous NiO/polyaniline film as anode for lithium ion batteriesX.H.Huang,J.P.Tu *,X.H.Xia,X.L.Wang,J.Y.XiangDepartment of Materials Science and Engineering,Zhejiang University,Hangzhou 310027,Chinaa r t i c l e i n f o Article history:Received 20May 2008Received in revised form 21June 2008Accepted 24June 2008Available online 29June 2008Keywords:NiO/polyaniline film AnodeLithium ion batterya b s t r a c tNickel foam-supported porous NiO film was prepared by a chemical bath deposition technique,and the NiO/polyaniline (PANI)film was obtained by depositing the PANI layer on the surface of the NiO film.The NiO film was constructed by NiO nanoflakes,and after the deposition of PANI,these nanoflakes were coated by PANI.As an anode for lithium ion batteries,the NiO/PANI film exhibits weaker polarization as compared to the NiO film.The specific capacity after 50cycles for NiO/PANI film is 520mAh g À1at 1C,higher than that of NiO film (440mAh g À1).The improvement of these properties is attributed to the enhanced electrical conduction and film stability of the electrode with PANI.Ó2008Elsevier B.V.All rights reserved.1.IntroductionTransition-metal oxide (MO,M =Fe,Co,Ni,and Cu)films have been extensively studied since these oxides were proposed by Tar-ascon’s team as anodes for lithium ion batteries [1–6].These oxides demonstrate capacities over 700mAh g À1,but for most of the unmodified films,the cycling performance is poor [7–9].This is re-lated to various factors,such as the conductivity,the structural sta-bility,and the aggregation extent of the Li-active nanoparticles.It is known that NiO is a semiconductor with low conductivity,and the pristine particles will be disintegrated after the first discharge reaction:NiO +2Li ?Ni +Li 2O,resulting in poor electrical contact between the Li-active nanoparticles and the substrate.Further-more,during the following cycling,the Li-active nanoparticles will be aggregated and form larger bulk particles,and lose the activity gradually.These factors result in poor cycling performances of NiO.To overcome these problems,an effective way is coating the pris-tine particles with a conductive layer [10].As a conductive polymer,polyaniline (PANI)can be used to im-prove the electrochemical properties of electrode materials for lithium ion batteries [11–15].In the present work,a NiO/PANI film with a porous net-like structure was prepared using nickel foam as the substrate.The PANI offer conductive pathways between the ac-tive particles,the current collector,and the electrolyte,and it also can accommodate the volume expansion via the polymer visco-elasticity and thus keep the porous net-like NiO stable during the discharge-charge.The nickel foam substrate leads to much moreactive material compared with the metal-foil substrate [16].Fur-thermore,the porous net-like structure of the NiO film offers a lar-ger electrode/electrolyte contact area and a shorter diffusion length of lithium ions.2.ExperimentalNickel foam-supported NiO film was prepared by CBD as re-ported elsewhere [7,17–18].The solution for the CBD was com-posed of 40mL of 1M NiSO 4,30mL of 0.25M K 2S 2O 8,10mL of aqueous ammonia (25–28%NH 3),and 20mL of deionized water.The deposition was carried out for 1h at room temperature using nickel foam as the substrate.After washed and dried,the sample was then calcined in a tube furnace at 350°C for 2h in flowing ar-gon.The NiO/PANI composite film was prepared by an electrode-position technique.The electrolyte consisted of 1mL distilled aniline and 100mL of 0.1M H 2SO 4.The deposition of PANI film was performed on a CHI660C electrochemical workstation by a cyclic voltammetry technique at a sweep rate of 30mV s À1be-tween À0.2and 1.5V for 5cycles,using the nickel foam-supported NiO film as the working electrode,a saturated calomel electrode as the reference electrode,and a Pt foil as the counter-electrode.The samples were characterized by X-ray diffraction (XRD,Rig-aku D/max-3B),Fourier transform infrared spectrometry (FTIR,Thermo Nicolet-380),scanning electron microscopy (SEM,FEI Siri-on-100)and transmission electron microscopy (TEM,JEOL JEM200CX).Calculated from the weight increment,the content of PANI in the composite film was 25wt.%.Test cells were assembled in an argon-filled glove box using the nickel foam-supported NiO or NiO/PANI film as working electrode,1388-2481/$-see front matter Ó2008Elsevier B.V.All rights reserved.doi:10.1016/j.elecom.2008.06.020*Corresponding author.Tel.:+8657187952573;fax:+8657187952856.E-mail address:tujp@ (J.P.Tu).Electrochemistry Communications 10(2008)1288–1290Contents lists available at ScienceDirectElectrochemistry Communicationsjournal homepage:www.else v i e r.c o m /l o c a t e /e l e c omLi foil as counter-electrode,polypropylene film as separator,and an electrolyte of 1M LiPF 6in a 50:50(w/w)mixture of ethylene car-bonate and diethyl carbonate.The cells were galvanostatically dis-charged and charged at the current density of 1C (718mA g À1)over a voltage of 0.02–3.0V vs.Li +/Li.Cyclic voltammetry (CV)tests were carried out using the CHI660C at a scanning rate of 0.5mV s À1between 0and 3V.3.Results and discussionFig.1shows the XRD patterns of the nickel foam-supported NiO and NiO/PANI films.The peaks at 37.3,43.3,and 62.9°in the pat-tern of nickel foam-supported NiO (Fig.1a)can be assigned to (111),(200),and (220)reflections of cubic NiO (JCPDS Card No.47-1049).These peaks can also be observed in the pattern of the NiO/PANI film (Fig.1b),indicating that the NiO film was not dis-solved in such an acidic electrolyte for the deposition of PANI.The FTIR spectrum of the NiO/PANI composite film is shown in Fig.2.The peak at 3410cm À1can be ascribed to –OH group of adsorbed water molecules.The characteristic peaks at 1580cm À1and 1500cm À1correspond to the quinoid ring (Q)and the benzene ring,respectively.The bands in the range 1200–1400cm À1are the C–N stretching band of an aromatic amine.The characteristic bandof polyaniline base is the N @Q @N stretching band at 1130cm À1[11,19].The band from 400to 800cm À1can be assigned to Ni–O.SEM and TEM images of the NiO and NiO/PANI films are given in Fig.3.The NiO film is constructed by many interconnected nano-flakes with a thickness of about 20nm (Fig.3a).The NiO flakes ar-range vertically to the substrate,forming a net-like structure and leaving pores of about 200nm.This film has a large electrode/elec-trolyte contact area and a short diffusion length of lithium ions,which is beneficial to get a high specific capacity and good cycling stability even at a high current density.After the deposition of PANI,the film maintains the porous net-like structure,but the20304050607080(b)(a)∗∗∗∗∗∗I n t e n s i t y (a .u .)2 thetaNiNiNi(220)(200)(111)∗NiOFig.1.XRD patterns of the nickel foam-supported (a)NiO and (b)NiO/PANI films.Fig.3.SEM images of the (a)NiO and (b)NiO/PANI film.The TEM image of a flake in each film inserts in the top-right.X.H.Huang et al./Electrochemistry Communications 10(2008)1288–12901289nanoflakes become thicker with a thickness of about80nm(Fig. 3b).The TEM images show that the NiOflake is very smooth,but the NiO/PANIflake exhibits a corrugated surface.It is concluded from the SEM and TEM images that the PANI layer was deposited on the surface of the NiOflake,and encapsulated it inside.CV curves of the NiO and NiO/PANIfilm electrodes are shown in Fig.4.For the NiO electrode,the reduction peak around1.23V cor-responds to the formation of the solid electrolyte interphase(SEI) layer,and the main reduction peak located at0.56V corresponds to the NiO+2Li?Ni+Li2O reduction[3,4].The oxidation peaks around0.75V and1.82V correspond to the partial decomposition of the SEI,and the main oxidation peak located at2.54V corre-sponds to the decomposition of Li2O[3,4].For the NiO/PANI elec-trode,the reduction peaks locate at1.26V and0.65V,and the three oxidation peaks locate at0.74,1.76,and2.45V,respectively. Obviously,polarization of the NiO/PANIfilm electrode is reduced compared with the NiO electrode,indicating better reversibility. This is because the conductive PANI improved the electrical con-tact between the NiOflakes,the substrate,and the electrolyte.Fig.5shows the capacity retention properties of the NiO and NiO/PANIfilm electrodes.An increased discharge capacity is observed for the NiO/PANIfilm electrode up to17cycles.Although the capacity is lower in thefirst few cycles,the NiO/PANI electrode exhibits better cycling performance.The specific capacity for NiO/PANI electrode after50cycles is520mAh gÀ1,higher than the NiO electrode(440mAh gÀ1).The improved cycling perfor-mance is attributed to the PANI.The PANI keeps the NiOflakes electrically connected,and it also offers conductive pathways be-tween the active particles,the substrate,and the electrolyte,and thus facilitates the charge transfer.The PANI can also keep the NiOflakes stable during the cycling.Fig.6shows the SEM images of the fully charged NiO and NiO/PANI electrodes.The porous NiOfilm was disintegrated and the particles aggregated severely after the cycling(Fig.6a).However,the porous net-like structure of NiO/PANIfilm is undamaged(Fig.6b),which indicates that the NiOflakes are stabilized by the PANI layer.4.ConclusionsNickel foam-supported NiO/PANIfilm was prepared.Thefilm has a porous net-like morphology,which was constructed by NiO nanoflakes coated by the PANI layer.Thisfilm exhibited weaker polarization,indicating better reversibility than the NiOfilm.The NiO/PANIfilm also exhibited better cycling performance than the NiOfilm.These improvements are attributed to the PANI,which enhanced the electrical conduction of the electrode and kept the NiOfilm stable during cycling.References[1]P.Poizot,ruelle,S.Grugeon,L.Dupont,J-M.Tarascon,Nature407(2000)496.[2]J.-M.Tarascon,M.Armand,Nature414(2001)359.[3]S.Grugeon,ruelle,R.Herrera-Urbina,L.Dupont,P.Poizot,J-M.Tarascon,J.Electrochem.Soc.148(2001)A285.[4]A.Débart,L.Dupont,P.Poizot,J-B.Leriche,J-M.Tarascon,J.Electrochem.Soc.148(2001)A1266.[5]rcher,G.Sudant,J-B.Leriche,Y.Chabre,J-M.Tarascon,J.Electrochem.Soc.149(2002)A234.[6]P.Poizot,ruelle,S.Grugeon,J-M.Tarascon,J.Electrochem.Soc.149(2002)A1212.[7]X.H.Huang,J.P.Tu,Z.Y.Zeng,J.Y.Xiang,X.B.Zhao,J.Electrochem.Soc.155(2008)A438.[8]Y.Wang,Y.-F.Zhang,H.-R.Liu,S.-J.Yu,Q.-Z.Qin,Electrochim.Acta48(2003)4253.[9]E.A.Souza,nders,L.P.Cardoso,Tersio G.S.Cruz,M.H.Tabacniks, A.Gorenstein,J.Power Sources155(2006)358.[10]X.H.Huang,J.P.Tu,C.Q.Zhang,J.Y.Xiang,mun.9(2007)1180.[11]Y.-G.Wang,W.Wu,L.Cheng,P.He,C.-X.Wang,Y.-Y.Xia,Adv.Mater.20(2008)2166.[12]Y.Mosqueda,E.Pérez-Cappe,J.Arana,E.Longo,A.Ries,M.Cilense,P.A.P.Nascente,P.Aranda,E.Ruiz-Hitzky,J.Solid State Chem.179(2006)308.[13]X.-W.Zhang,C.Wang,A.J.Appleby,F.E.Little,J.Power Sources109(2002)136.[14]M.Lira-Cantú,P.Gómez-Romero,Int.J.Inorg.Mater.1(1999)111.[15]M.Malta,R.M.Torresi,Electrochim.Acta50(2005)5009.[16]Y.Yu,C.-H.Chen,J.-L.Shui,S.Xie,Angew.Chem.Int.Ed.44(2005)7085.[17]P.Pramanik,S.Bhattacharya,J.Electrochem.Soc.137(1990)3869.[18]S.-Y.Han,D.-H.Lee,Y.-J.Chang,S.-O.Ryu,T.-J.Lee,C.-H.Chang,J.Electrochem.Soc.153(2006)C382.[19]Y.-G.Wang,H.-Q.Li,Y.-Y.Xia,Adv.Mater.18(2006)2619.Fig.6.SEM images of the fully charged(a)NiO and(b)NiO/PANI electrodes after20cycles.1290X.H.Huang et al./Electrochemistry Communications10(2008)1288–1290。