R

Ab

PP

a

ARRAA

KLSCXI

C

uEccpmnmp

P

0d

Electrochimica Acta 55 (2010) 6332–6341

Contents lists available at ScienceDirect

Electrochimica Acta

journa l homepage: www.e lsev ier .com/ locate /e lec tac ta

eview article

review of the features and analyses of the solid electrolyte interphase in Li-ionatteries

allavi Verma, Pascal Maire1, Petr Novák ∗,1

aul Scherrer Institut, Electrochemistry Laboratory, CH-5232 Villigen PSI, Switzerland

r t i c l e i n f o

rticle history:eceived 8 March 2010eceived in revised form 20 May 2010ccepted 22 May 2010vailable online 1 June 2010

a b s t r a c t

The solid electrolyte interphase (SEI) is a protecting layer formed on the negative electrode of Li-ionbatteries as a result of electrolyte decomposition, mainly during the first cycle. Battery performance,irreversible charge “loss”, rate capability, cyclability, exfoliation of graphite and safety are highly depen-dent on the quality of the SEI. Therefore, understanding the actual nature and composition of SEI is of

eywords:i-ion batteryolid electrolyte interphase (SEI)arbon (graphite)-ray photoelectron spectroscopy (XPS)

prime interest. If the chemistry of the SEI formation and the manner in which each component affectsbattery performance are understood, SEI could be tuned to improve battery performance. In this paperkey points related to the nature, formation, and features of the SEI formed on carbon negative electrodesare discussed. SEI has been analyzed by various analytical techniques amongst which FTIR and XPS aremost widely used. FTIR and XPS data of SEI and its components as published by many research groupsare compiled in tables for getting a global picture of what is known about the SEI. This article shall serve

nfrared spectroscopy (FTIR) as a handy reference as well as a starting point for research related to SEI.© 2010 Elsevier Ltd. All rights reserved.

ontents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63332. Formation and features of the SEI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6333

2.1. Components of SEI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63332.2. Changes in SEI at elevated temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63342.3. Influence of SEI on battery performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63342.4. Influence of SEI on exfoliation of graphite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6335

3. Factors affecting SEI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63353.1. Type of carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63353.2. Pretreatment of carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63353.3. Electrolyte composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6336

3.4. Other factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4. Characterization of SEI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.1. Fourier transform infrared spectroscopy (FTIR) . . . . . . . . . . . . . . . . . . . .4.2. Limitations of FTIR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Abbreviations: AAS, atomic absorption spectroscopy; AES, Auger electron spectroscoated total reflectance; BET, Brunauer–Emmett–Teller; DEC, diethyl carbonate; DMC, dimELS, electron energy loss spectroscopy; EIS, electrochemical impedance spectroscopy;hemical quartz crystal microbalance; ESCA, electron spectroscopy for chemical analyshromatography; ICL, irreversible charge “loss”; IRAS, infrared absorption spectroscopy;olyethylene oxide; PVDF, polyvinylidene difluoride; PVDF-HFP, polyvinylidene difluoridicroscopy; SIMS, secondary ion mass spectroscopy; SNIFTIR, subtractively normalized in

ing tunneling microscopy; TEM, transmission electron microscopy; THF, tetrahydrofuranass spectroscopy; TPD, temperature programmed desorption; UHV, ultra high vacuum;

hotoelectron spectroscopy; XRD, X-ray diffraction.∗ Corresponding author at: Paul Scherrer Institut, Department General Energy, Electroc

SI, Switzerland. Tel.: +41 56 310 2457; fax: +41 56 310 4415.E-mail address: petr.novak@psi.ch (P. Novák).

1 ISE member.

013-4686/$ – see front matter © 2010 Elsevier Ltd. All rights reserved.oi:10.1016/j.electacta.2010.05.072

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6336

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6336. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6337. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6339

py; AFM, atomic force microscopy; ARC, accelerated rate calorimetry; ATR, atten-ethyl carbonate; DSC, differential scanning calorimetry; EC, ethylene carbonate;

ELSA, elemental line scan analysis; EMC, ethyl methyl carbonate; EQCM, electro-is; FIB, focused ion beam; FTIR, Fourier transform infrared spectroscopy; IC, ionk, rate constant; NMR, nuclear magnetic resonance; PC, propylene carbonate; PEO,

e-hexafluoropropylene; SEI, solid electrolyte interphase; SEM, scanning electronterfacial Fourier transform infrared; SPM, scanning probe microscopy; STM, scan-; ToF-MS, time of flight-mass spectroscopy; ToF-SIMS, time of flight-secondary ionVC, vinylene carbonate; XANES, X-ray absorption near edge structure; XPS, X-ray

hemistry Laboratory, Electrochemical Energy Storage Section, CH-5232 Villigen

P. Verma et al. / Electrochimica Acta 55 (2010) 6332–6341 6333

4.3. X-ray photoelectron spectroscopy (XPS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63394.4. Limitations of XPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6339

5. Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63405.1. Features of an ideal SEI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6340Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6340

. . . . . .

1

acrbutAbrdgadaw

cmnimgoehL

gftftdncgfhI

ctSlllT

2

aam

tions may be present in the SEI. Hence, all the possible (reported)inorganic components are not listed in Table 1. We list the mostplausible and common SEI components along with their referencesto the best of our knowledge.

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Introduction

Li-ion batteries have replaced the conventional batteries likelkaline, Ni–Cd, and lead acid batteries in a wide range of appli-ations, ranging from microelectronics to aerospace. The primeeason for this sweep is up to two times higher voltage of Li-ionattery (∼3.6 V) compared to aqueous batteries (∼1.2–2 V) andp to six times higher gravimetric specific energy of Li-ion bat-ery (∼240 Wh/kg [1]) compared to lead acid battery (∼40 Wh/kg).fter decades of intensive research on each component of Li-ionatteries, they can now be titled as one of the most widely usedechargeable systems. Li-ion batteries are also prospective can-idates for use in electric vehicles. However, the very facts thative Li-ion batteries an edge over the alkaline and Ni–Cd batteriesre also the bottlenecks of this technology. Wide voltage windowemands the use of non-aqueous electrolytes. But the known non-queous solvents are thermodynamically instable in this voltageindow.

The state of the art Li-ion battery is also called the “rockinghair” battery [2]. It comprises of insertion materials as activeaterials [3]. The Li-ions shuttle back and forth between the

egative and positive electrodes during cycling. The electrochem-stry of a typical Li-ion battery is shown in Fig. 1. By far, the

ost common active material used in the negative electrodes israphite (C6 + xLi+ + xe− �C6Lix). However, there are innumerousther kinds of carbons which have also been used [4]. As positivelectrode mostly transition metal oxides [5] and phosphates [6]ave been employed, out of which LiCoO2 [7], LiMn2O4 [8], andiFePO4 [9] are the most common ones.

During first charge of the Li-ion battery the electrolyte under-oes reduction at the negatively polarized graphite surface. Thisorms a passive layer comprising of inorganic and organic elec-rolyte decomposition products. In an ideal case this layer preventsurther electrolyte degradation by blocking the electron transporthrough it while concomitantly allowing Li-ions to pass throughuring cycling. This essential passive layer has appropriately beenamed solid electrolyte interphase (SEI) [10]. Some solvents such asyclic alkyl carbonates [11] form effective passive layers that ensureood cycling stability of the negative electrodes. An overview of theundamental concepts and principles of the SEI was published inandbooks like “Handbook of Battery Materials” [12] and “Lithium-

on Batteries: Solid-Electrolyte Interphase” [13].This review describes some vital features of the SEI on graphitic

arbons. Some fundamental questions are discussed, like what fac-ors affect the SEI and how the SEI affects battery performance.ubstantial work has been done in the past few decades on ana-yzing the SEI and spelling out its components. In this paper, theiterature of SEI on graphite is compiled with a detailed compi-ation of the X-ray photoelectron spectroscopy (XPS) and Fourierransform Infrared (FTIR) data of the SEI components.

. Formation and features of the SEI

As lithiated carbons are not stable in air, a Li-ion battery islways assembled in its discharged state that means with graphitend lithiated positive materials. The electrolyte solution is ther-odynamically unstable at low and very high potentials vs. Li/Li+.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6340

Hence, on first charge of the cell the electrolyte solution begins toreduce/degrade on the graphite surface and forms the SEI.2 Thereare competing and parallel solvent and salt reduction processes,which result in deposition of a number of organic and inorganicdecomposition products on the surface of graphite. On the wholethis layer imparts kinetic stability to the electrolyte against furtherreductions in the successive cycles and thereby ensures good cycla-bility of the electrode. The SEI also prevents solvent co-intercalationand hence exfoliation of graphites [14].

The onset potential of SEI formation is not a fixed value. Litera-ture offers values such as 2 V [15], 1.7 V [16], or 1 V [14], but 0.8 V[17,18] is the most widely adopted practical value. SEI formationmay also continue up to few cycles. However, this parameter can-not be normalized because it depends on a number of factors likenature and composition of electrolyte, nature of additives used inthe electrolyte [19], sweep rates [20], etc. It is desirable to havecomplete SEI formation before Li-ion intercalation begins (>0.3 V[21]). It is more difficult to achieve this for disordered carbons asthe intercalation begins from 1.5 V as compared to ordered carbonswhere it begins at 0.25 V [15].

SEI is a very complicated layer comprising of inorganic compo-nents which are normally salt degradation products and organiccomponents which are partial or complete reduction products ofthe solvent of the electrolyte. The thickness of the SEI may varyfrom few Å to tens or hundreds of Å [18,22]. It is difficult to dis-tinctly measure the SEI thickness as some of the components arepartially soluble in the electrolyte [23]. But as formation of a newphase between active material and the electrolyte modifies theinterphase resistance, the average thickness was estimated usingelectrochemical impedance spectroscopy (EIS) [24]. The picture ofa real SEI inside the battery has always been blur. Models of theSEI on graphite were proposed by Peled et al. [25], Aurbach [21,24],and Edström et al. [18,26]. They all suggest SEI to be a dense layerof inorganic components close to the carbon, followed by a porousorganic or polymeric layer close to the electrolyte phase. Some-times crystals of LiF are also detected [27].

2.1. Components of SEI

The composition of the SEI is a highly debated subject. It ishighly dependent on numerous factors, which are detailed in Sec-tion 3. Proposed composition of SEI varies from one research groupto another as operating conditions in different laboratories can bedifferent. Thus it is impossible to normalize or generalize the com-position or even contents of SEI. Table 1 lists what various researchgroups believe to be the major components of the SEI. A largenumber of inorganic salts (precipitates) originating from salt reduc-

2 The reduction occurs on all surfaces at the same potential, in particular on thecurrent collector too. However, because of the low surface area of the latter thereaction at graphite is predominant.

6334 P. Verma et al. / Electrochimica Acta 55 (2010) 6332–6341

F ector;i tor.

2

titmptSatlcotepeaS

TC

ig. 1. Schematic illustration of a typical Li-ion battery: (a) aluminum current collnhomogeneous SEI layer; (e) graphite active material and (f) copper current collec

.2. Changes in SEI at elevated temperatures

The SEI composition and thickness does not stay constanthroughout cycling or storage [50]. There are many different waysn which it can transform. It may partially dissolve in a solvent ofhe electrolyte, e.g., dimethyl carbonate (DMC) [51]. Its thickness

ay also vary during cycling. SEI is believed to be thicker at lowerotentials (lithiated state of carbon) and thinner at higher poten-ials (delithiated state) [17]. However the changes appearing in theEI are more pronounced at elevated temperatures [52,53]. Therere two prime reactions that occur on elevating battery tempera-ure. First transformation of SEI occurs. Here, the components likeithium alkyl carbonates and semicarbonates convert to the stableomponents like Li2CO3. However, the temperature at which thisccurs is highly dependent on the salt and solvent of the electrolyte,ype of carbon material, and its specific surface area. For 1 M LiPF6 in

thylene carbonate (EC) and diethylcarbonate (DEC) the onset tem-erature was found to be 105 ◦C [54]. Whereas for LiBF4 containinglectrolytes it was as low as 60 ◦C [55]. The second process occurringt high temperature is the reaction of active material with the SEI, orEI with the electrolyte, or active material with the electrolyte. This

able 1ontents of the SEI as reported in the literature.

Component Present Not present Notes

(CH2OCO2Li)2 [11,15,28–30] Being a two elSEI of the EC b

ROCO2Li [11,15,19,29,31] They are presepropylene carthe electrolyte

Li2CO3 [11,31–33] [16,27,34,35] Not always prmay also appe

ROLi [15,16,35–39] Most commonmay also appeproduct [40].

LiF [27,32,34] Mostly foundmajor salt redbyproduct. Am

Li2O [34,43,44] [18,26,27] It may be a dePolycarbonates [27,45] Present in the

flexibility to thLiOH [30,46,47] [27,43] It is mainly fo

Li2O with watLi2C2O4 [35,39] It is found to b

LiPF6 in EC:EM[35].

HCOLi [19] It is present w

(b) oxide active material; (c) porous separator soaked with liquid electrolyte; (d)

begins at 120–140 ◦C [55]. At this temperature, the transformed SEIallows Li from carbon to come into contact with the electrolyte andelectrons to pass through the SEI. Beyond this temperature, evenmore exothermic reactions like that of lithiated carbon with binders(e.g. polyvinylidene difluoride-hexafluoropropylene (PVDF-HFP) at350 ◦C) occur [51]. All these exothermic processes are detrimentalfor the performance of a Li-ion battery and are critical from thesafety point of view. Thus they are carefully examined by thermoanalytical technique such as differential scanning calorimetry [56]and accelerated rate calorimetry [57].

2.3. Influence of SEI on battery performance

Every parameter and property of the SEI significantly affectsbattery performance. The composition, thickness, morphology, andcompactness are a few to name. Irreversible charge “loss” (ICL) in

the first cycle occurs due to solvent reduction and SEI formation andis hence a characteristic of SEI [58]. Detrimental processes occur-ring during storage (self-discharge) also depend on the ability ofthe SEI to passivate active material surface. Hence, shelf-life of abattery also depends on SEI [59]. As mentioned above SEI may also

ectron reduction product of ethylene carbonate (EC); it is found mostly in theased electrolytes.nt in the outer layer of the SEI and are absent near Li [32]. They occur in most

bonate (PC) containing electrolytes, especially when the concentration of PC inis high.

esent [18]. Normally present in the SEI formed in EC or PC based electrolytes. Itar as a reaction product of semicarbonates with HF or water or CO2.ly found in the SEI formed in ether electrolytes like tetrahydrofuran (THF), butar as dimethyl carbonate (DMC) or ethyl methyl carbonate (EMC) reduction

It is soluble and may thus undergo further reactions [41].in electrolytes comprising of fluorinated salts like LiAsF6, LiPF6, LiBF4. It is auction product. HF contaminant also reacts with semi carbonates to give LiFount of LiF increases during storage [42].

gradation product of Li2CO3 during Ar+ sputtering in the XPS experiment.outermost layer of the SEI, close to the electrolyte phase. This part impartse SEI.

rmed due to water contamination [48,49]. It may also result from reaction ofer or with ageing [35].e present in 18650 cells assembled in Argonne National Labs containing 1.2 MC (3:7) electrolyte. Li carboxylate and Li methoxide were also found in their SEI

hen methyl formate is used as co-solvent or additive.

ica Acta 55 (2010) 6332–6341 6335

diedstc

2

itco(itTirsatesfhbfib

3

naemr

3

tdcntasshaapatpOgttoi

P. Verma et al. / Electrochim

issolve and/or evolve during cycling. Thus, effective and stable SEIs mandatory for good cycling life of the battery [60]. It becomesven more important during cycling at high rates and at deeperepth of discharge [61]. SEI components are highly temperatureensitive. Thus, performance of the battery at high/low tempera-ure is dependent on the SEI [62]. However the most importantonsequence of SEI is on the safety of the battery [63,64].

.4. Influence of SEI on exfoliation of graphite

The mechanism of SEI passivating the active material surfacemparting kinetic stability and ensuring good cycling may some-imes fail. The effective SEI formation may be hindered by the otherhemical reactions. One of the causes of this failure is exfoliationf graphite which is a common occurrence in propylene carbonatePC) based electrolytes [33]. Two mechanisms have been proposedn the literature explaining the reason and mechanism of exfolia-ion of graphite. The first model was given by Besenhard et al. [14].hey proposed that solvent molecules co-intercalate along with Li-ons between the graphene sheets of graphite. Then the secondaryeactions of graphite intercalated compounds distort the orderedtructure of the graphite [14]. The second model by Aurbach [40]rgues that solvent co-intercalation is only limited to ether elec-rolytes, PC based electrolytes rather reduce on the crevices on thedge planes to release gaseous byproducts (propylene). The pres-ure of the gas cracks the particles and exposes fresh surface forurther reactions. Their supporting argument is that exfoliation isighly dependent on the morphology and 3D structure of the car-on [40]. But both the authors conclude by suggesting the usage oflm forming additives like CO2, N2O, Sx

2− [65], and vinylene car-onate (VC) or Li disalicilatoborate salt [66] for averting exfoliation.

. Factors affecting SEI

Many vital factors contribute to properties of the SEI. There iso absolute parameter circumscribing the SEI. It is the combinationnd concomitant effect of all these factors which dictates the prop-rties, quality, and efficiency of SEI. Hence, the resulting influence ofany factors listed in this section is collective and interdependent

ather than independent.

.1. Type of carbon

Since SEI is an interphase between the active material andhe electrolyte, it’s obvious that properties of both these phasesominate the SEI. SEI is essentially formed on the surface of thearbonaceous negative active material, thus the type of carbon sig-ificantly affects the SEI. Winter et al. showed that ICL attributedo SEI formation is linearly proportional to the BET specific surfacerea of the carbon [67]. Zheng et al. found that the crystallographictructure and particle morphology are as influential as BET specificurface area [50]. They showed that coke and graphite powdersaving same BET specific surface area exhibit different ICL [50]. Inddition, edges and surface imperfections like defects, crevices, andctive sites act as catalytic sites for solvent reduction. Hence, theylay an important role in solvent reduction kinetics. Dangling bondsnd high current density on these sites favor electrolyte reduc-ion. Thus concentration and nature of defects, and edge to basallane ratio [68] are also critical factors affecting SEI properties.n similar lines our group correlated the active surface area of the

raphites with film forming and ICL [69–71]. In general, the SEI onhe cross section of the electrode and the edges of the graphite par-icles contain more inorganic components like LiF whereas the SEIn the graphene sheets contain soft organic compounds as shownn a schematic sketch of SEI in Fig. 2. Even though the surface is

Fig. 2. Sketch of a lithiated graphite composite electrode covered by inhomoge-neous SEI. The SEI components shown in darker shades of grey are mainly inorganicwhile those shown in lighter shades of grey are organic.

very important for SEI formation the importance of the crystal-lographic structure of the carbon should not be underestimated.Highly ordered carbons are more vulnerable to exfoliation and arethus more sensitive to electrolyte composition. Therefore, crystal-lographic order significantly affects the extent of exfoliation andco-intercalation of solvents [15,33].

3.2. Pretreatment of carbon

Once the importance of the surface properties of the materialwas understood, efforts were made to modify the surface mor-phology and chemistry of the carbons by various methods. Surfacetreatments of vast diversity were experimented upon. Scott et al.[72] performed reduction of their electrodes in butyl-lithium solu-tions for varying durations of time to decrease the ICL. The SEIformed was thicker but more brittle. Ein-Eli and Koch [73] oxidizedthe graphite powders with HNO3 and (NH4)2S2O8 and enhancedthe specific charge capacity of graphite. This was attributed to theproduction of cavities or nanovoids during oxidation (etching). Panet al. used a different approach of chemical treatment. Instead ofaltering the surface groups already present on the carbon surface,they immobilized aryl functional groups onto carbon to facilitatethe SEI formation on these groups [74,75]. But the success waslimited in terms of suppression of the ICL. Electrochemical treat-ments like electroless plating of graphite by Cu were also tried. Thedischarge capacity and columbic efficiency were found to improve[76].

The next category of the surface treatments of carbons is thethermal treatments. The main target of these treatments is to obtainhigh specific charge capacity carbons, which can accommodatemore than one Li+ per C6. It was mainly done by pyrolysis of differ-ent organic precursors at various temperatures. Work done in thisfield has been reviewed by Zheng et al. [77]. There are also treat-ments combining two or more methods. For example, Ohzuku etal. [78] improved the performance of graphite fiber anode by heattreating acetylene black and graphite at 700 ◦C. They ascribed theamelioration to removal of hydroxyl groups and water from the sur-face. Aiming at similar targets many other methods were reported.

The literature cited above and the references there within are justa few examples to illustrate the wide variety of treatments per-formed. A detailed discussion of this subject is beyond the scope ofthis review.

6 mica Acta 55 (2010) 6332–6341

3

trciawedvrc[

oRauMeawtteRTspt[a[Z

ooccsttSpSocsswhthtpr

3

c[pt

336 P. Verma et al. / Electrochi

.3. Electrolyte composition

The SEI composition and contents are a direct consequence ofhe electrolyte composition. Thermodynamic instability and kineticeactivity of the electrolyte culminates into the SEI. Some featuresan be derived from Table 1. For example, lithium alkoxides appearn the SEI formed in ether electrolytes, semicarbonates and Li2CO3ppear in SEI formed in carbonate electrolytes (EC and PC) [15],hile lithium formate occurs in SEI formed in methyl formate

lectrolyte [19]. The decomposition products of various solventsepend on the solvents dielectric constant, polarity, reactivity [19],iscosity [14], etc. These parameters are also vital selection crite-ia of the solvents for suitable electrolytes. Reactivity of commonarbonate based electrolytes are in the order EC > PC > DMC > DEC19].

A study specifically on EC and PC showed that when the ECr PC concentration in the electrolyte is high, (CH2OCO2Li)2 orOCO2Li are the major reduction products respectively. Howevert low EC or PC concentration Li2CO3 is the major reduction prod-ct [15]. Presence of Li2CO3 was extensively studied in the 1990s.ost of the studies by Aurbach’s group [11,28,31,33] showed pres-

nce of Li2CO3. In another study they showed that Li2CO3 wasbsent in the SEI formed in dry THF solution, but on addition ofater (>40 ppm) or PC (1 M), Li2CO3 precipitates [15]. In contrast,

he studies in 2000s reported much less Li2CO3 in the SEI owingo more controlled conditions of analyses [16,27,34,35]. In gen-ral, (CH2OCO2Li)2 and Li2CO3 are better passivating agents thanOLi and ROCO2Li because they are less soluble in the solvents.hese studies were in close agreement with another study whichhowed that EC reduction products are insoluble and hence moreassivating [11]. Further, on addition of reactive additives the reac-ion pathways change depending on the nature of the additive11]. Aurbach’s group reported enhanced Li2CO3 content in the SEInd hence improved battery performance by using CO2 as additive19,28]. The effect of additives in electrolyte has been reviewed byhang [79].

Rather more complicated chemistry occurs during the reductionf salts. The correlation of the nature of salt with the compositionf SEI was studied by Aurbach et al. [80]. The system gets moreomplex in the presence of HF, which appears in the electrolytesontaining fluorinated salts like LiAsF6, LiPF6, etc. Aurbach et al.tated that Li2CO3 in the SEI can disappear by reaction with HF inhe electrolytes containing LiPF6 and LiBF4 [19,28]. Effect of addi-ional HF on SEI was studied on LiPF6 in EC:DMC electrolyte byato et al. [81]. The main consequence of HF in the electrolyte is therecipitation of LiF, which forms an integral inorganic part of theEI [18]. In order to predict the solvent reduction products and theverpotential they required for their formation; Peled et al. [32] cal-ulated rate constants of reactions between solvated electrons withalts and solvents of the electrolyte. They correlated these rate con-tants to the potential at which the corresponding SEI componentould form. The main conclusion of this study was that materialsaving low k (rate constant) need a higher overpotential for forma-ion and thus form at lower potentials vs. Li/Li+, while those thatave high k are formed at higher potential vs. Li/Li+. This study illus-rates the pronounced effect of kinetics on the SEI formation. Goodrecursors or additives can enhance electrolyte reduction kineticsesulting in a faster SEI formation.

.4. Other factors

In addition to the chemical factors affecting SEI, the electro-hemical conditions also play a significant role. Mode of cycling82], mode of polarization (galvanostatic, potentiostatic cycling orotential sweeps, etc.) [15,62], and overpotential [32] are a fewo mention. Temperature during cycling, SEI formation, and bat-

Fig. 3. SEM of composite SFG6 (TIMCAL®) graphite electrode (90% graphite and 10%PVDF-HFP binder): (a) pristine electrode and (b) electrode after one cycle vs. Li metalin 1 M LiPF6 in EC:DMC (1:1) electrolyte at C/10 rate.

tery storage is critical because it has a direct consequence on thereaction kinetics [83].

4. Characterization of SEI

Analyzing pristine SEI is a tedious task. Some of the fundamentalfacts which make the SEI analysis a challenge are summarized inthis section. SEI is a very thin layer adhering to the active materialsurface (Fig. 3). It is almost impossible to demarcate the boundarybetween the end of the SEI and beginning of the electrolyte. So, it isalways tricky to justify what thickness of the surface layer on carbonone wishes to analyze. Peeling off the SEI from carbon surface toois difficult and almost impossible to be performed precisely. In themethods which measure the SEI along with the electrolyte or afterwashing with solvents of the electrolyte, there is always an uncer-tainty as to which component actually belongs to the SEI and whichone is from the electrolyte or is a side-product of the separation pro-cedure. Moreover the functional groups and chemical compositionof the solvents and SEI components are very similar, thus differen-tiating between the two is always difficult. It is unlikely that the SEIpreserves its pristine nature after steps of separation, washing, andisolation. There are many possibilities of SEI components undergo-ing modification and degradation during these procedures. Most of

the components of SEI are highly sensitive to contamination, air,and humidity. ROCO2Li and ROLi may convert to Li2CO3 by react-ing with CO2 [29]. ROCO2Li reacts with water to form Li2CO3, CO2,and ROH [49]. Other alkyl lithium carbonates react with water toform LiOH or Li2CO3 [84]. Li reacts with O2 to form Li2O, Li2O2,

P. Verma et al. / Electrochimica Acta 55 (2010) 6332–6341 6337

Table 2FTIR data of the SEI components as reported in the literature.

Component Functional group Vibration (cm−1)

(CH2OCO2Li)2 C O asym st 1634 [19], 1650 [11], 1654 [29]CH2 bend 1396 [19], 1400–1450 [11,29]C O sym st 1300 [19], 1301 [29], 1320–1290 [11]C–O st 1050 [19], 1100–1070 [11], 1083 [29]OCO2 bend 822 [29], 840–820 [11]

ROCO2Li C–H 2950–2820 [42], 2930–2850 [11]C O asym st 1610 [15], 1650 [11,15,84], 1668 [29], 1685 [43], 1680–1640 [42]CH2 bend 1450–1400 [11,42]C O sym st 1300 [15], 1350 [43], 1350–1300 [42], 1350–1320 [11,84]C–O st 1060–1020 [24], 1090 [15], 1100 [42], 1115 and 1044 [43], 1100–1050 [84], 1100–1080 [11]CO3 bend 820 [42,84], 855 [43], 840–80 [11]

Li2CO3 C–O st 1400 [35], 1470–1450 [84], 1450 and 1500 [29], 1510–1450 [15], 1520–1480 [11], 1520–1500[84], 1542–1455 [43]

CO32− bend 875 [11], 876 [43], 879 [29], 890–870 [15]

ROLi C–H st 2963 [15], 2900–2700 [84]C–O st 1000 [15], 1050 [119], 1080 [15], 1100–1000 [84]Li–O st 600–500 [84]

Li2O Li–O st 600 [15,84]RCOOLi C O asym st 1500–1700 [35]LiOH O–H st 3670 [35], 3675 [84], 3660–3675 [43]Li2C2O4 C O st 1640 [35]

9], 1620 [12

5]

awa

rbcwledlgt

rattfIridttlt

•••

•••••

HCOOLi C O st 1606 [1COO− bend 1380, 79

PVDF (as binder, not SEI component) C–F st 1200 [1

nd LiO2. All of these are strong nucleophiles and react furtherith organic solvents and semicarbonates to form carbonates and

lkoxides [84].For ex situ analysis a transfer or encapsulating mechanism is

equired, which allows the sample to be transported from the gloveox (inert atmosphere) to the analysis chamber of any analyti-al machine without exposure to air and humidity. For machineshich operate under ultra high vacuum (UHV) or high vacuum

ike XPS, scanning electron microscopy (SEM), and transmissionlectron microscopy (TEM) these devices are even more difficult toesign. Orisini et al. designed a movable airlock [85] for recording

ive SEM images of dendrites formation on lithium [86]. Tarascon’sroup used similar transfer techniques for studying SEI via otherechniques like FTIR and TEM as well [87].

A large variety of techniques have been used for analyzing SEIanging from spectroscopy to microscopy to diffraction and thermonalysis. Since SEI is a surface phenomenon the surface analysisechniques like XPS, AES, AFM, SIMS, ToF-MS, STM (all abbrevia-ions listed below) are most frequently used. SEM and TEM are usedor imaging the surface film. Vibration spectroscopies like FTIR,RAS, Raman, and XANES also provide valuable surface informationegarding the functionality. EIS is used to study the evolution of thenterphase resistance. Diffraction techniques like XRD are used foretermining the ordering and structure of SEI. Thermo analyticalechniques like DSC, ARC, and TPD are used to study various reac-ions like SEI formation and degradation. And finally the techniquesike NMR and AAS give bulk information of SEI components. Theseechniques along with corresponding citations are listed below.

AES (Auger electron spectroscopy) [30,43]AFM (atomic force microscopy) [48,88–91]TOF-SIMS (time of flight-secondary ion mass spectroscopy)[68,92–94]

STM (scanning tunneling microscopy) [95,96]SPM (scanning probe microscopy) [97]SEM (scanning electron microscopy) [30,98]TEM (transmission electron microscopy) [87,99]IRAS (infrared absorption spectroscopy) [43]

0 [120]0], [19]

• Raman spectroscopy [83,100]• XRD (X-ray diffraction) [27,99,100]• EELS (electron energy loss spectroscopy) [99]• XANES (X-ray absorption near edge structure) [93,101,102]• EIS (electrochemical impedance spectroscopy)

[83,98–100,103–106,31]• DSC (differential scanning calorimetry) [51,64,107]• ARC (accelerated rate calorimetry) [54,108–112]• TPD (temperature programmed desorption) [30,70,113]• NMR (nuclear magnetic resonance) [99,114,115]• AAS (atomic absorption spectroscopy) [30]• EQCM (electrochemical quartz crystal microbalance) [38]• IC (ion chromatography) [30]• FIB and ELSA (secondary electron focused ion beam and elemental

line scan analysis) [37]

In this review the analyses of the SEI by FTIR and XPS will be com-piled. These two techniques are not only highly surface sensitivebut are also complementary to each other. Information from thesetwo techniques put together provides a good picture of the SEI. Theother reason for confining this study to FTIR and XPS is that theseare amongst the most widely used techniques for the SEI analysis.These have been used by numerous research groups and abundantFTIR and XPS data exists in the literature about SEI and its variouscomponents. Thus, it will be useful to compile this data into onetable which is easier to compare, interpret, and comprehend. Thiswill also constructively define facts like relative error between dif-ferent studies on similar material and general trends. But beforeinterpreting the data values, it is worthwhile to compare the prosand cons of both FTIR and XPS analysis techniques.

4.1. Fourier transform infrared spectroscopy (FTIR)

The FTIR spectroscopy is a very versatile tool for the analy-sis of the chemistry of a substance. Beams of wavelength in therange 100 �m and 1 �m interact with the material during theexperiment. Thus UHV conditions are not mandatory for theseinstruments. This makes FTIR spectroscopy comparatively cheaper

6338P.V

erma

etal./Electrochim

icaA

cta55 (2010) 6332–6341

Table 3XPS data of the SEI components as reported in the literature.

SEI component Binding energy (eV)

C 1s O 1s F 1s Li 1s B 1s P 1s Cl 2p

LiF 685.9 [121], 686 [26,122],685–686 [11], 686.2[44,123], 686.4 [32],686–686.5 [27]

56 [121,124], 56.4 [44],56.5 [26], 56.2–56.6 [27]

Li2O 528.3 [122], 527.6 [43],528.7 [44,123,125],528–529 [18]

53 [43], 53.7 [44,122,125],54 [18]

LiPF6 688 [27,122] 138 [27]

Li2CO3 290 [26,43], 290.1 [121],290.5 [44], 289.8–290.2[123], 291.5 [27,126]

531.5 [43], 531–532 [18],532 [26], 532.5 [44], 532.7[121], 533.5–534 [27]

55.3 [43], 55.5[18,26,121,125], 56.5 [27]

LiBF4 688.2 [26], 688.5–689 [27], 57 [27], 58 [26] 196.3 [26], 196.5 [27]

ROCO2Li 287.6 [126], 289 [44],289–290 [27,124], 288–292[53]

532.2 [44], 533 [53] 55 [44]

LiOH 531.5 [43], 531.9 [44,127],532 [125]

55.5 [125], 55.3 [43,44]

LiCl 198.4 [43], 199[32,121], 200 [11]

PVDF 290.5 [126] 688 [11]

PEO 286.5 [26,27] 533 [26]

Other polymeric species 284.8 [44], 285.5–286.5 [27]

Li2C2 282.4 [125], 282.5 [121], 283[124]

Li 52.3 [121,125]

C sp2 284.2 [126], 284.3 [26], 284.4[44], 285 [26,44,125]

P. Verma et al. / Electrochimica Acta 55 (2010) 6332–6341 6339

Table 4Deconvolution of the C 1s, O 1s, Li 1s, and F 1s spectra of SEI as reported in the literature.

Assignment

C 1s photoelectron peak position (eV)282.5 [44] Li2C2

283.7 [44], 284 [16], 284.3 [27], 284.4 [11,17,114,127], 284.8 [27], 285 [122] C–H, sp2 carbon285.5 [123], 286 [121], 286.1 [128], 287 [124] C–OH285.5 [27,44,124] Polymers in SEI286.5 [17,40] (–CH2CH2O–)n

285 [121], 285.5 [123], 286 [18,122], 286.5 [16,27,123] C–O–C287–288 [27], 287 [43], 286–287 [123] Ether carbon in various environment287 [121], 287.3 [128] C O287.6 [126], 289–290 [27], 289.1 [128] C–(OR)(CO2Li) or COOR288–291 [16], 290 [123], 290.6 [43,128] RO–CO2Li (alkyl lithium carbonates)

O 1s photoelectron peak position (eV)532.4 [127], 533.8 [43], 534.5 [27] RO–CO2Li (various carbonates)532.5 [123], 533 [27,121,127], 534 [121,127] C–O–C or C–O–H531 [121,127] C O530.8 [121] C–O–Li

Li 1s photoelectron peak position (eV)54 [18] Li–O55.5 [18] Li–CO3

55 [121] Li–O–C

tsgogtutiurtiu

4

tabTaahCahl[wioe

4

y

F 1s photoelectron peak position (eV)688.8 [123]685–686.4 [123], 684.8 [129]683.5 [129]

han other techniques which need UHV due to use of high energyources like XPS. FTIR differentiates between different functionalroups based on their dipole moment. Thus vibrational energyf various bonds is characteristic of the corresponding functionalroup. Tables listing characteristic vibrations for different func-ional groups can be found in many textbooks [116]. There arencountable publications reporting FTIR spectra of the SEI on Li,he SEI on graphite, and of synthesized components of SEI. Its possible to use IR spectroscopy in various modes like atten-ated total reflectance (ATR), photoacoustic infrared, diffusedeflectance infrared, subtractively normalized interfacial Fourierransform infrared (SNIFTIR), transmission infrared, near normalncidence reflectance, grazing incidence reflectance, double mod-lation infrared [43], and reflection absorption infrared.

.2. Limitations of FTIR

The limitations of analyzing the SEI by FTIR can be divided intowo parts. First, the limitations are due to the nature of the SEInd second due to the limitations of the spectroscopy itself. The SEIeing a thin surface layer may not give very strong vibration signals.he composition of the SEI is inhomogeneous; perhaps a mappingnalysis would be needed for distinguishing between componentsnd their distribution. Moreover, the various components of the SEIave very similar functional groups, mainly carbonyls, alkoxides,–H vibrations, etc. This makes the spectra interpretation tricky,s it is difficult to distinguish between the various componentsaving overlapping vibration signals. The limitations of molecu-

ar spectroscopy itself lie in its quantum mechanic fundamentals117]. More polar bonds are generally more intense than the oneshich are less polar. Some principal SEI components like LiF are

nfrared inactive. It is difficult to make quantitative analysis basedn the intensities of the various signals. Large absorption by thelectrolytes makes in situ analysis of electrodes challenging.

.3. X-ray photoelectron spectroscopy (XPS)

XPS, also known as electron spectroscopy for chemical anal-sis (ESCA) employs X-rays of high energy (∼1200–1500 eV).

P–FLi–FNa–F

During an XPS measurement the high energy X-ray photons (AlK� = 1486.6 eV, Mg K� = 1253.6 eV) are incident on the sample. Coreelectrons are ejected as photoelectrons which are then captured bythe analyzer and sent to the detector. Various photoelectrons aredifferentiated on the basis of the kinetic energy with which theyare ejected. Their kinetic energy is proportional to the energy of thelevel from which the electron is ejected. XPS allows analysis of allelements (except H and He) present in concentration > 0.1 atomicpercentage in the outermost 10 nm of the surface [118]. It is a semiquantitative technique with error in the range ±10%. The chemicalshifts in the binding energies give information about the molecularenvironment of the element. Thus C–C, C–O, C O can be differenti-ated from within the C 1s signal. The resolution of the XPS is ∼0.1 eV.The penetration depth is ∼50 Å [17]. The non-destructive elemen-tal depth profile with the angular dependent XPS (∼10 nm) andthe destructive elemental depth profile with ion etching (severalhundreds of nm) are the techniques used for depth analysis.

4.4. Limitations of XPS

Due to the use of highly energetic photons for excitation of thesample, the risk of radiation damage exists. The highly energeticbeam spot may lead to degradation of the SEI components and mayalter their chemical nature. Quantification becomes complicatedwhen the substrate and the surface have the same elements. Forthe non-conductive samples, the spectrum shifts to lower kineticenergy; this is called “charging”. The calibration of the spectra inthis case becomes tricky. The size of this shift depends on the con-ductivity and the microstructure of the component and is thusdifficult to rectify precisely. During the destructive depth analysis ofinhomogeneous films, the etching rate is not the same for hard andsoft components. The hard inorganic materials need longer sputter-ing time to etch a particular depth as compared to the soft organicmaterial. Etching may also lead to modification of the surface and

reactions of the active species to form undesirable products.

XPS data analysis and interpretation is not trivial. Developinga suitable model for the chemical nature of the species presentbased on the deconvoluted high resolution spectra requires preciseknowledge of the system and good reference values. However, the

6 mica A

baa

wdvp1Tc

5

psadifcphItpa

5

Ltwipppcab

sS

A

R

340 P. Verma et al. / Electrochi

inding energy values of atoms in specific chemical environmentvailable in the literature vary widely. This makes the assignments,nd hence model development difficult.

Hence in spite of the limitations, FTIR and XPS are the two mostidely used techniques for analysis of the SEI. Tables 2 and 3 list theata available in the literature from the FTIR and XPS analysis of thearious components of the SEI. Since many organic components areresent in the SEI, deconvolution and analysis of the C 1s, O 1s, Lis, and F 1s spectra are crucial for comprehending the information.he deconvoluted binding energies of these elements in differenthemical environments are compiled in Table 4.

. Conclusion

A good SEI on negative electrode is a prerequisite for gooderformance of a Li-ion battery. Studying, analyzing, and under-tanding the SEI have underlined the significance of the manyspects related to it. It is evident that there are many inter-ependent and correlated factors influencing the SEI and many

nterdependent and correlated consequences of SEI on battery per-ormance. On one hand, factors affecting SEI properties are type ofarbon material, pretreatment of carbon material, electrolyte com-osition, and electrochemical and physical conditions. On the otherand, the battery performance parameters affected by the SEI are

CL, self-discharge, cyclability, rate capability, and safety. Amongsthe various techniques used to analyze the SEI, FTIR and XPS haveroved to be very useful. To conclude this review properties desir-ble in an efficient SEI are summarized.

.1. Features of an ideal SEI

An ideal SEI should have minimum electronic and maximumi+ conductivity. SEI formation kinetics should be fast, allowing ito form completely before the onset of Li+ intercalation. In otherords, SEI formation potential should be more positive than Li+

ntercalation potential. An ideal SEI should have uniform mor-hology and composition. It should contain stable and insolubleassivating agents like Li2CO3 rather than metastable and poorlyassivating ones like ROLi and ROCO2Li [15]. A good SEI should be aompact layer adhering well to the carbon. It should be elastic [40]nd flexible [130] to accommodate non-uniform electrochemicalehavior and active material breathing.

Therefore, all the facts and figures compiled in this review articlehall serve as a handy reference to any field of interest related toEI in Li-ion battery research.

cknowledgement

We thank Swiss National Science Foundation for funding.

eferences

[1] Panasonic, Green Car Green Car Congress, post 1 October 2009.[2] D. Guyomard, J-M. Tarascon, Adv. Mater. 6 (2004) 408.[3] M. Winter, J.O. Besenhard, M.E. Spahr, P. Novak, Adv. Mater. 10 (1998) 725.[4] M. Endo, C. Kim, K. Nishimura, T. Fujino, K. Miyashita, Carbon 38 (2000) 183.[5] T. Ohzuku, A. Ueda, Solid State Ionics 69 (1994) 201.[6] D. Morgan, A. Van der Ven, G. Ceder, Electrochem. Solid State Lett. 7 (2004)

A30.[7] K. Ozawa, Solid State Ionics 69 (1994) 212.[8] M.M. Thackeray, A. Dekock, M.H. Rossouw, D. Liles, R. Bittihn, D. Hoge, J.

Electrochem. Soc. 139 (1992) 363.[9] A.K. Padhi, K.S. Nanjundaswamy, J.B. Goodenough, J. Electrochem. Soc. 144

(1997) 1188.[10] E. Peled, J. Electrochem. Soc. 126 (1979) 2047.[11] D. Aurbach, B. Markovsky, A. Shechter, Y. Ein-Eli, H. Cohen, J. Electrochem.

Soc. 143 (1996) 3809.[12] E. Peled, D. Golodnitsky, J. Penciner, The anode/electrolyte Interface, in: J.O.

Besenhard (Ed.), Handbook of Battery Materials, Wiley-VCH, 1999, p. 419.

cta 55 (2010) 6332–6341

[13] P.B. Balbuena, Y. Wang, Lithium-Ion Batteries: Solid-Electrolyte Interphase,Imperial College Press, London, 2004.

[14] J.O. Besenhard, M. Winter, J. Yang, W. Biberacher, J. Power Sources 54 (1995)228.

[15] D. Aurbach, M.D. Levi, E. Levi, A. Schechter, J. Phys. Chem. B 101 (1997) 2195.[16] S.H. Kang, D.P. Abraham, A. Xiao, B.L. Lucht, J. Power Sources 175 (2008) 526.[17] H. Bryngelsson, M. Stjerndahl, T. Gustafsson, K. Edström, J. Power Sources 174

(2007) 970.[18] K. Edström, M. Herstedt, D.P. Abraham, J. Power Sources 153 (2006) 380.[19] Y. Ein-Eli, B. Markovsky, D. Aurbach, Y. Carmeli, H. Yamin, S. Luski, Elec-

trochim. Acta 39 (1994) 2559.[20] C. Liebenow, M.W. Wagner, K. Lühder, P. Lobitz, J.O. Besenhard, J. Power

Sources 54 (1995) 369.[21] D. Aurbach, J. Power Sources 89 (2000) 206.[22] T. Yoshida, M. Takahashi, S. Morikawa, C. Ihara, H. Katsukawa, T. Shiratsuchi,

J. Yamaki, J. Electrochem. Soc. 153 (2006) A576.[23] D. Alliata, R. Kotz, P. Novak, H. Siegenthaler, Electrochem. Commun. 2 (2000)

436.[24] A. Zaban, D. Aurbach, J. Power Sources 54 (1995) 289.[25] E. Peled, D. Golodnitsky, G. Ardel, J. Electrochem. Soc. 144 (1997) L208.[26] A.M. Andersson, A. Henningson, H. Siegbahn, U. Jansson, K. Edström, J. Power

Sources 119–121 (2003) 522.[27] A.M. Andersson, K. Edstrom, J. Electrochem. Soc. 148 (2001) A1100.[28] D. Aurbach, Y. Eineli, B. Markovsky, A. Zaban, S. Luski, Y. Carmeli, H. Yamin, J.

Electrochem. Soc. 142 (1995) 2882.[29] D. Aurbach, Y. Gofer, M. Benzion, P. Aped, J. Electroanal. Chem. 339 (1992)

451.[30] A. Kominato, E. Yasukawa, N. Sato, T. Ijuuin, H. Asahina, S. Mori, J. Power

Sources 68 (1997) 471.[31] D. Aurbach, A. Zaban, J. Electroanal. Chem. 348 (1993) 155.[32] E. Peled, D. Golodnitsky, C. Menachem, D. Bar-Tow, J. Electrochem. Soc. 145

(1998) 3482.[33] D. Aurbach, Y. Eineli, O. Chusid, Y. Carmeli, M. Babai, H. Yamin, J. Electrochem.

Soc. 141 (1994) 603.[34] E. Peled, D. Bar Tow, A. Merson, A. Gladkich, L. Burstein, D. Golodnitsky, J.

Power Sources 97–98 (2001) 52.[35] G.R.V. Zhuang, P.N. Ross, Electrochem. Solid State Lett. 6 (2003) A136.[36] S. Mori, H. Asahina, H. Suzuki, A. Yonei, K. Yokoto, J. Power Sources 68 (1997)

59.[37] H.L. Zhang, F. Li, C. Liu, J. Tan, H.M. Cheng, J. Phys. Chem. B 109 (2005) 22205.[38] D. Aurbach, M. Moshkovich, J. Electrochem. Soc. 145 (1998) 2629.[39] A. Augustsson, M. Herstedt, J.H. Guo, K. Edstrom, G.V. Zhuang, P.N. Ross, J.E.

Rubensson, J. Nordgren, Phys. Chem. Chem. Phys. 6 (2004) 4185.[40] D. Aurbach, J. Power Sources 119–121 (2003) 497.[41] D. Aurbach, B. Markovsky, I. Weissman, E. Levi, Y. Ein-Eli, Electrochim. Acta

45 (1999) 67.[42] D. Aurbach, Y. Einely, A. Zaban, J. Electrochem. Soc. 141 (1994) L1.[43] K.-I. Morigaki, A. Ohta, J. Power Sources 76 (1998) 159.[44] D. Bar-Tow, E. Peled, L. Burstein, J. Electrochem. Soc. 146 (1999) 824.[45] S. Genies, PhD thesis, L’Institut National Polytechnique de Grenoble, France,

1998, p. 226.[46] K. Kanamura, H. Tamura, Z. Takehara, J. Electroanal. Chem. 333 (1992) 127.[47] M. Odziemkowski, D.E. Irish, J. Electrochem. Soc. 140 (1993) 1546.[48] D. Aurbach, Y. Cohen, J. Electrochem. Soc. 143 (1996) 3525.[49] D. Aurbach, M.L. Daroux, P.W. Faguy, E. Yeager, J. Electrochem. Soc. 134 (1987)

1611.[50] T. Zheng, A.S. Gozdz, G.G. Amatucci, J. Electrochem. Soc. 146 (1999) 4014.[51] A. Du Pasquier, F. Disma, T. Bowmer, A.S. Gozdz, G. Amatucci, J.M. Tarascon,

J. Electrochem. Soc. 145 (1998) 472.[52] H.H. Lee, C.C. Wan, Y.Y. Wang, J. Electrochem. Soc. 151 (2004) A542.[53] G.R. Zhuang, Y.F. Chen, P.N. Ross, Langmuir 15 (1999) 1470.[54] M.N. Richard, J.R. Dahn, J. Electrochem. Soc. 146 (1999) 2068.[55] D.D. MacNeil, D. Larcher, J.R. Dahn, J. Electrochem. Soc. 146 (1999) 3596.[56] F. Joho, P. Novak, M.E. Spahr, J. Electrochem. Soc. 149 (2002) A1020.[57] J.W. Jiang, J.R. Dahn, Electrochim. Acta 49 (2004) 4599.[58] K. Zaghib, G. Nadeau, K. Kinoshita, J. Electrochem. Soc. 147 (2000) 2110.[59] R. Yazami, Y.F. Reynier, Electrochim. Acta 47 (2002) 1217.[60] P. Novák, J.C. Panitz, F. Joho, M. Lanz, R. Imhof, M. Coluccia, J. Power Sources

90 (2000) 52.[61] N. Ogihara, Y. Igarashi, A. Kamakura, K. Naoi, Y. Kusachi, K. Utsugi, Electrochim.

Acta 52 (2006) 1713.[62] A.V. Churikov, Electrochim. Acta 46 (2001) 2415.[63] G. Park, H. Nakamura, Y. Lee, M. Yoshio, J. Power Sources 189 (2009) 602.[64] Z. Zhang, D. Fouchard, J.R. Rea, J. Power Sources 70 (1998) 16.[65] J.O. Besenhard, M.W. Wagner, M. Winter, A.D. Jannakoudakis, P.D. Jan-

nakoudakis, E. Theodoridou, J. Power Sources 44 (1993) 413.[66] D. Aurbach, J.S. Gnanaraj, W. Geissler, M. Schmidt, J. Electrochem. Soc. 151

(2004) A23.[67] M. Winter, P. Novak, A. Monnier, J. Electrochem. Soc. 145 (1998) 428.[68] E. Peled, D. Golodnitsky, A. Ulus, V. Yufit, Electrochim. Acta 50 (2004) 391.

[69] P. Novák, J. Ufheil, H. Buqa, F. Krumeich, M.E. Spahr, D. Goers, H. Wilhelm, J.

Dentzer, R. Gadiou, C. Vix-Guterl, J. Power Sources 174 (2007) 1082.[70] S.H. Ng, C. Vix-Guterl, P. Bernardo, N. Tran, J. Ufheil, H. Buqa, J. Dentzer, R.

Gadiou, M.E. Spahr, D. Goers, P. Novak, Carbon 47 (2009) 705.[71] M.E. Spahr, H. Buqa, A. Würsig, D. Goers, L. Hardwick, P. Novák, F. Krumeich,

J. Dentzer, C. Vix-Guterl, J. Power Sources 153 (2006) 300.

ica A

P. Verma et al. / Electrochim

[72] M.G. Scott, A.H. Whitehead, J.R. Owen, J. Electrochem. Soc. 145 (1998) 1506.[73] Y. Ein-Eli, V.R. Koch, J. Electrochem. Soc. 144 (1997) 2968.[74] Q. Pan, H. Wang, Y. Jiang, Electrochem. Commun. 9 (2007) 754.[75] Q. Pan, H. Wang, Y. Jiang, J. Mater. Chem. 17 (2007) 329.[76] Z. Liu, A. Yu, J.Y. Lee, J. Power Sources 81–82 (1999) 187.[77] T. Zheng, Y.H. Liu, E.W. Fuller, S. Tseng, U. Vonsacken, J.R. Dahn, J. Electrochem.

Soc. 142 (1995) 2581.[78] T. Ohzuku, Y. Iwakoshi, K. Sawai, J. Electrochem. Soc. 140 (1993) 2490.[79] S.S. Zhang, J. Power Sources 162 (2006) 1379.[80] D. Aurbach, I. Weissman, A. Zaban, O. Chusid, Electrochim. Acta 39 (1994) 51.[81] T. Sato, M. Deschamps, H. Suzuki, H. Ota, H. Asahina, S. Mori, Symposium

on Materials for Electrochemical Energy Storage and Conversion II-Batteries,Capacitors and Fuel Cells, at the 1997 MRS Fall Meeting, December 01–05,Boston, MA, 1997.

[82] J. Li, E. Murphy, J. Winnick, P.A. Kohl, J. Power Sources 102 (2001) 302.[83] S.S. Zhang, K. Xu, T.R. Jow, Electrochim. Acta 49 (2004) 1057.[84] D. Aurbach, Y. Gofer, J. Langzam, J. Electrochem. Soc. 136 (1989) 3198.[85] F. Orsini, A. du Pasquier, B. Beaudouin, J.M. Tarascon, M. Trentin, N. Langen-

huizen, E. de Beer, P. Notten, J. Power Sources 81–82 (1999) 918.[86] M. Dolle, L. Sannier, B. Beaudoin, M. Trentin, J.M. Tarascon, Electrochem. Solid

State Lett. 5 (2002) A286.[87] M. Dollé, S. Grugeon, B. Beaudoin, L. Dupont, J.M. Tarascon, J. Power Sources

97–98 (2001) 104.[88] F.P. Campana, H. Buqa, P. Novák, R. Kötz, H. Siegenthaler, Electrochem. Com-

mun. 10 (2008) 1590.[89] S.K. Jeong, M. Inaba, R. Mogi, Y. Iriyama, T. Abe, Z. Ogumi, Langmuir 17 (2001)

8281.[90] S.K. Jeong, M. Inaba, Y. Iriyama, T. Abe, Z. Ogumi, 11th International Meeting

on Lithium Batteries, June 24–28, Monterey, CA, 2002.[91] R. Mogi, M. Inaba, S.K. Jeong, Y. Iriyama, T. Abe, Z. Ogumi, J. Electrochem. Soc.

149 (2002) A1578.[92] E. Peled, D.B. Tow, A. Merson, A. Gladkich, L. Burstein, D. Golodnitsky, J. Power

Sources 97–8 (2001) 52.[93] H. Ota, T. Akai, H. Namita, S. Yamaguchi, M. Nomura, J. Power Sources 119–121

(2003) 567.[94] G. Gachot, S. Grugeon, M. Armand, S. Pilard, P. Guenot, J.-M. Tarascon, S.

Laruelle, J. Power Sources 178 (2008) 409.[95] M. Inaba, Y. Kawatate, A. Funabiki, S.-K. Jeong, T. Abe, Z. Ogumi, Electrochim.

Acta 45 (1999) 99.[96] E. Peled, C. Menachem, D. BarTow, A. Melman, J. Electrochem. Soc. 143 (1996)

L4.[97] S.-K. Jeong, M. Inaba, Y. Iriyama, T. Abe, Z. Ogumi, J. Power Sources 119–121

(2003) 555.

[98] Q.C. Zhuang, L.L. Tian, G.Z. Wei, Q.F. Dong, S.G. Sun, Chin. Sci. Bull. 54 (2009)

2627.[99] M.C. Smart, B.V. Ratnakumar, S. Surampudi, Y. Wang, X. Zhang, S.G. Green-

baum, A. Hightower, C.C. Ahn, B. Fultz, J. Electrochem. Soc. 146 (1999) 3963.[100] Q.C. Zhuang, J.M. Xu, J.H. Tian, X.Y. Fan, Q.F. Dong, S.G. Sun, Chem. J. Chin. Univ.

Chin. 29 (2008) 973.

cta 55 (2010) 6332–6341 6341

[101] T. Akai, H. Ota, H. Namita, S. Yamaguchi, M. Nomura, Phys. Scripta T115 (2005)408.

[102] H. Ota, T. Akai, H. Namita, S. Yamaguchi, M. Nomura, 11th International Meet-ing on Lithium Batteries, June 24–28, Monterey, CA, 2002.

[103] C.S. Wang, A.J. Appleby, F.E. Little, J. Electroanal. Chem. 497 (2001) 33.[104] C.S. Wang, A.J. Appleby, F.E. Little, J. Electroanal. Chem. 519 (2002) 9.[105] S.S. Zhang, K. Xu, T.R. Jow, 6th International Symposium on Electrochemical

Impedance Spectroscopy, May 16–21, Cocoa Beach, FL, 2004.[106] M. Itagaki, N. Kobari, S. Yotsuda, K. Watanabe, S. Kinoshita, M. Ue, J. Power

Sources 135 (2004) 255.[107] E.-G. Shim, T.-H. Nam, J.-G. Kim, H.-S. Kim, S.-I. Moon, J. Power Sources 172

(2007) 901.[108] M.N. Richard, J.R. Dahn, J. Power Sources 83 (1999) 71.[109] U. von Sacken, E. Nodwell, A. Sundher, J.R. Dahn, J. Power Sources 54 (1995)

240.[110] U. von Sacken, E. Nodwell, A. Sundler, J.R. Dahn, Solid State Ionics 69 (1994)

284.[111] J. Jiang, J.R. Dahn, Electrochim. Acta 49 (2004) 4599.[112] M.N. Richard, J.R. Dahn, J. Electrochem. Soc. 146 (1999) 2078.[113] H. Ota, T. Sato, H. Suzuki, T. Usami, J. Power Sources 97–98 (2001) 107.[114] L. Gireaud, S. Grugeon, S. Laruelle, S. Pilard, J.M. Tarascon, J. Electrochem. Soc.

152 (2005) A850.[115] Y. Dai, Y. Wang, V. Eshkenazi, E. Peled, S.G. Greenbaum, J. Electrochem. Soc.

145 (1998) 1179.[116] P. Clerc, S. Simon, Tables of Spectral Data for Structure Determination of

Organic Compounds, Springer-Verlag, 1989.[117] C.N. Banwell, E.M. McCash, Fundamentals of Molecular Spectroscopy, Tata

McGraw-Hill Publishing Company, 1995 (Chapter 3).[118] J.C. Vickerman, Surface Analysis—The Principal Techniques, John Wiley and

Sons, Ltd. Publication, 2009.[119] H. Yoshida, T. Fukunaga, T. Hazama, M. Terasaki, M. Mizutani, M. Yamachi, J.

Power Sources 68 (1997) 311.[120] Y. Ein-Eli, D. Aurbach, Langmuir 8 (1992) 1845.[121] K. Kanamura, H. Tamura, S. Shiraishi, Z.-I. Takehara, J. Electroanal. Chem. 394

(1995) 49.[122] K. Edstrom, M. Herstedt, D.P. Abraham, J. Power Sources 153 (2006) 380.[123] V. Eshkenazi, E. Peled, L. Burstein, D. Golodnitsky, Solid State Ionics 170 (2004)

83.[124] D. Aurbach, I. Weissman, A. Schechter, H. Cohen, Langmuir 12 (1996) 3991.[125] K. Kanamura, S. Shiraishi, H. Tamura, Z. Takehara, J. Electrochem. Soc. 141

(1994) 2379.[126] L. Zhao, I. Watanabe, T. Doi, S. Okada, J.-I. Yamaki, J. Power Sources 161 (2006)

1275.

[127] M. Lu, H. Cheng, Y. Yang, Electrochim. Acta 53 (2008) 3539.[128] C. Moreno-Castilla, M.V. López-Ramón, F. Carrasco-Marín, Carbon 38 (2000)

1995.[129] Y. Kawamoto, K. Ogura, M. Shojiya, M. Takahashi, K. Kadono, J. Fluorine Chem.

96 (1999) 135.[130] D. Aurbach, E. Zinigrad, Y. Cohen, H. Teller, Solid State Ionics 148 (2002) 405.