In Situ Generation of Poly (Vinylene Carbonate) Based Based Carbonate) (Vinylene of Poly Generation in Situ

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, - 1 − [2–4] Lee 1600377 The The [9] Since Since C. ° S cm [11,12] 7 However, However, − [1] (1 of 9) , but not for , but not for 4 [3,4,6,8–10] These merits [7]

C and 60 and C

° 2 www.advancedscience.com the existence of liquid electrolyte wileyonlinelibrary.com The succinonitrile based solid The succinonitrile based solid [8] [5,6] - Although some strategies in the modifica tion of separator could improve the per formance of lithium ion batteries to some extent, the conventional lithium ion battery using the conventional lithium ion battery using nonaqueous liquid electrolytes encounters - safety issues, i.e., fire or explosion haz a ards, when they are closely packed into large format module, especially for electric vehicles. These issues stimulate intensive safety and high energy interest in high density solid state lithium batteries. 1. Introduction has gained extensive Lithium ion battery and portable in application successful and electronic devices. consumable always is closely related to a hidden safety always is closely related to a hidden safety - hazard. The solid electrolyte is a key com ponent for ensuring high safety and high Among solid state electro- voltage window. Moreover, it is generally regarded that its it is generally regarded that its Moreover, [13,14] at ambient temperature due to the presence of –1 at , which could be well suitable for LiFePO −1 + S cm 3 Till now, three categories of solid polymer electrolytes (SPEs) three categories of solid polymer electrolytes (SPEs) now, Till − this solid electrolyte system has attracted extensive interests this solid electrolyte system has attracted extensive interests in academic field as well as industrial community. qualify them promising materials for high energy solid state qualify them promising materials for high battery. (PEO) Polyoxyethylene i.e., reported, extensively been have based solid electrolyte, succinonitrile based solid electrolyte, and polyester based solid polymer electrolyte. branched PEO based solid polymer electrolyte has been com- the main chains of However, mercialized by DAISO (Japan). the hamper to temperature room at crystallize readily PEO ion migration resulting in a lower ionic conductivity at room temperature. 10 electrolytes possessed ultrahigh ionic conductivity above electrolytes possessed ultrahigh ionic conductivity above unique plastic–crystalline phase between –40 between phase plastic–crystalline unique the high voltage cathodes. Wright and Armand discovered that the PEO based electrolyte discovered that the PEO based electrolyte and Armand Wright possessed considerable ionic conductivity above 10 and co-workers developed a facile strategy to prepare polymerand lytes, solid polymer electrolyte takes the advantage of high flex- lytes, solid polymer electrolyte takes the resistance when and low interfacial easy processability, ibility, compared with inorganic ceramic electrolyte. electrochemically stability window is lower than 4.0 V versus electrochemically stability window is lower than 4.0 V versus Li/Li S cm −5 /Li batteries 2 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2016 The Authors. Published by WILEY-VCH Verlag © and considerable ionic conductivity of 9.82 × 10 and considerable ionic conductivity of +

2016, 1600377

Sci. www.MaterialsViews.com C. Moreover, it is demonstrated that high voltage LiCoO 50 °C. Moreover, Adv. This is an open access article under the terms of the Creative Commons Commons This is an open access article under the terms of the Creative Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Nowadays it is extremely urgent to seek high performance solid polymer urgent to seek high performance Nowadays it is extremely lithium/graphitic both interfacial stability toward electrolyte that possesses energy density solid state bat- anodes and high voltage cathodes for high effect of vinylene carbonate additive teries. Inspired by the positive interfacial (vinylene carbonate) based solid on solid electrolyte interface, a novel poly in situ polymerization process in polymer electrolyte is presented via a facile It is manifested that poly (vinylene carbonate) based solid polymer this paper. stability window up to 4.5 V electrolyte possess a superior electrochemical versus Li/Li Jingchao Chai, Zhihong Liu,* Jun Ma, Jia Wang, Xiaochen Liu, Haisheng Liu, Liu, Haisheng Liu, Xiaochen Wang, Zhihong Liu,* Jun Ma, Jia Jingchao Chai, Chen Guanglei Cui,* and Liquan Jianjun Zhang, Solid Electrolyte with Interfacial Stability for LiCoO for Stability with Interfacial Electrolyte Solid In Situ Generation of Poly (Vinylene Carbonate) Based Based Carbonate) (Vinylene of Poly Generation In Situ

using this solid polymer electrolyte display stable charge/discharge profiles, using this solid polymer electrolyte display and decent safety excellent cycling performance, considerable rate capability, carbonate) based electrolyte characteristic. It is believed that poly (vinylene electrolyte candidate for high energy can be a very promising solid polymer density lithium batteries. Lithium Batteries DOI: 10.1002/advs.201600377 Dr. J. Chai, Prof. Z. Liu, Dr. J. Ma, Dr. J. Wang, J. Wang, J. Ma, Dr. J. Chai, Prof. Z. Liu, Dr. Dr. J. Zhang, Prof. G. Cui H. Liu, Dr. Dr. Qingdao Industrial Energy Storage Institute Technology Qingdao Institute of Bioenergy and Bioprocess Technology Chinese Academy of Sciences Qingdao 266101, China E-mail: [email protected]; [email protected] J. Zhang Dr. J. Wang, J. Chai, Dr. Dr. University of Chinese Academy of Sciences Beijing 100049, China X. Liu Dr. of Chemistry and Molecular Engineering College Qingdao University of Science & Technology 266042 Qingdao, China Prof. L. Chen Matter Physics Beijing National Laboratory for Condensed Institute of Physics Chinese Academy of Sciences Beijing 100190, China Full paper 1600377 temperature. solutions wouldreducetheimpedanceofcathodesatambient energy lithiumbatteries. was believedtobepromisingsolid polymerelectrolyteforhigh decent ratecapability, andexcellent cyclingperformance,which lithium batteries. kind oftechniqueforpreparingsolidpolymerelectrolytein technique. Insitupolymerizationwasreportedtobesucha excellent electrochemicalpropertiesandfacilepreparation high performancesolidpolymerelectrolytesthatpossessboth cedures andcostaswell.So,itisextremelyurgenttoseek a largeamountofsolventsandincreasedthefabricationpro- were madebyexsitusolutioncastingtechnique,whichused However, mostofpolyester-based solidpolymerelectrolytes order of10 based solidelectrolyteshowedanionicconductivityofthe batteries. Ithasbeenfoundthatpoly(ethylenecarbonate)- have achievedgreatsuccessinhighperformanceoflithium solid stateLiCoO network-integrated plastic–crystallineelectrolyteforflexible promising unsaturatedadditives. tive) conditions.Typically, vinylenecarbonate(VC)isoneof polymerization underelectrochemicallyreductive(oroxida- functional groups (double or triple bonds) provide a site for additives innonaqueouselectrolytes,becauseunsaturated Unsaturated compoundshavealwaysbeenselectedassuch odes, consequentlyendowingbettercyclingperformance. ibility towardlithium/graphiticanodesandhighvoltagecath- nonaqueous electrolytestoenhancetheinterfacialcompat- cess ofsolidpolymerelectrolyteandcutsthecostfabrication. both electrodes.Thisstrategysimplifiesthepreparationpro- electrolytes would have an excellent contact and affinity with injected intothebatteries.Inaddition,insitugeneratedsolid monomers or precursors are liquid state, which facilitate to be trolyte interface(SEI)ongraphite. be electrochemicallyreducedtogenerateunstablesolidelec- cated that succinonitrile possessing two nitrile groups might voltage LiCoO demonstrated thatthissolidpolymer electrolyteendowedhigh generated viaafacileinsitu polymerization process.Itwas batteries. polymer electrolytecandidateforhighenergydensitylithium that PVCAbasedelectrolytecanbeaverypromisingsolid as-generated PVCAoninterfacialcompatibility, itisbelieved could obtainhighperformancepolymerelectrolyte. some gelpolymerelectrolytebyinsitupolymerization,which poly(propylene carbonate) teries. Somepolyester-based solidpolymerelectrolytes,suchas severely limiteditsapplicationforhighenergysolidstablebat- trile wouldreactwithlithiumfoilanodes.Thosedrawbacks formance of the batteries. improved thecompatibilityofinterfacialandcyclingper process, resultinginthemainingredientsofSEIlayersand on thesurfaceofgraphiticanodeduringcharge/discharge VC could be polymerized into poly(vinyl carbonate) (PVCA) have anumberofpotentialapplicationsinLi-O poly(methyl methacrylate-styrene)-basedpolymerelectrolytes www.advancedscience.com Some SEIadditivesarefrequentlyusedinstate-of-the-art Herein, thisnovelPVCAbased solidpolymerelectrolytewas (2 of9) − 5 [25] Scm 2 Inspiredbythepositiveinterfacialeffect ofthe /Li batteriesstablecharge/discharge profiles, wileyonlinelibrary.com 2 [20,21] /Li − 1 at30° 4 Ti Kangandco-workershave prepared 5 O [26] [4] 12 andpoly(ethylenecarbonate), C. In addition, the presence of VC in batteries. [17] Zhouetal.alsoreportedthat [24,25] [16] Itwasreportedthatthe [15] Inaddition,succinoni- However, itwasindi- © 2016TheAuthors.Published byWILEY-VCHVerlag GmbH&Co. KGaA,Weinheim 2 batteries. [21] The [22,23] [17,18] [19] -

and the absorption peak at 3166 cm FTIR spectracomparisoninFigure 1bthatafter polymerization lyze thechemicalstructureofPVCA.Ascanbeseenfrom and lithiumtetrafluoroborate(LiBF combined chemical structures of lithium bis(oxalate) borate kind oflithiumsaltusedinbatteries,possessingthe a Information). Lithiumdifluoro(oxalate)borate(LiDFOB)is persity (PDI,M Figure mally initializedradicalinitiatorat60° Liquid VCcanbepolymerizedintoPVCAcatalyzedbyather 2.1. InSituPolymerizationandCharacterizationofPVCA 2. ResultsandDiscussion NMR, and weight (M tion chromatographindicatedthattheweight-averagemolecular spectra verifiedthechemicalstructureofPVCA. shifted from130to76ppm,respectively. BothFTIRandNMR shifted from8.0to5.7ppm,andthecarbonchemicalshift was zation, theprotonchemicalshift ofCH occurred ataround2976cm cross-section image showedthatthethicknessofobtained face contactbetweenelectrolyte andelectrode.Inadditionthe strate. Thedensecoatinglayer wouldimprovesolid/solidinter dense coatinglayeronthesurface ofcellulosenonwovensub- smooth, whichmeantthatPVCA-LiDFOB had developeda seen fromFigure 2cthatthesurfaceofPVCA-SPE wasquite face morphologyandcross-sectionofPVCA-SPE. Itcouldbe ning electronmicroscope(SEM)wasusedtoobservethesur due to cellulose fibers’ induction (shown in Figure 2b). Scan- lyte (hereafter abbreviatedas“PVCA-SPE”) becametranslucent the compositecellulose/PVCA-LiDFOB solidpolymerelectro- parent. After incorporating into a cellulose nonwoven substrate, Information), whichwasconsistentwiththeresultofDSC. lization peakinX-ray diffraction (seeninFigure S4,Supporting water presentinthesample.Inaddition,therewasnocrystal - loss at around100° (seen inFigure S3,Supporting Information).Thefirstweight significance forthesafetyimprovementoflithiumbatteries. volatile untilahightemperatureof250° LiDFOB hadasuperiorthermalstabilitythatbeingnegligibly ture. ThermogravimetricanalysiscurvedisplayedthatPVCA- which meantthatPVCA-LiDFOB wasanamorphousstruc- LiDFOB atthetemperaturerangebetween–50and100° atom inC intermolecular interactionbetweenthelithiumionandoxygen Supporting Information),whichwasduetotheformationof temperature property. trolytes possessedsuperiorionicconductivityandelevated after insitupolymerizationwerefurtherconfirmedby single bond.ThechemicalstructurechangesofVCtoPVCA chemical structurechangeoftheC transition temperature (T curve showed that PVCA-LiDFOB had a slightly higher glass- salt inthispaper. Differential scanningcalorimetry(DSC) It could be seen in 13 C NMRspectrum(seeninFigure 1c,d).After polymeri- 1 a). Fourier transforminfraredspectroscopy(FTIR),  w ) ofPVCAcouldbeupto4.8× O. AndthereisnoobviousmeltingpeakforPVCA- 13 C NMRmeasurementswereconductedtoana- w / M n ) was2.77(seeninFigure S1,Supporting C was related to the evaporation of trace C wasrelatedtotheevaporation of trace [23,28] Figure g So, LiDFOB was adopted as lithium So,LiDFOBwasadoptedaslithium ) than PVCA (shown in Figure S2, − 1 2a that PVCA-LiDFOB was trans- , which were well assigned to the , whichwerewellassignedtothe − 1 disappeared and a new peak disappearedand a new peak 4  ). TheLiDFOB-basedelec- C doublebondinto  C for 24 h (shown in C for24h(shownin www.MaterialsViews.com C, which was of great C, whichwasofgreat CH double bond was CH doublebondwas 10 Adv. 5 andthepolydis- [27] Sci. Gel-permea- 2016, 1600377 1 H NMR H NMR  1 C, C, H C - - - Full paper 1600377 (3 of 9) www.advancedscience.com . 6 wileyonlinelibrary.com C NMR spectra of VC and PVCA in DMF-d 13 , and d) 6 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2016 The Authors. Published by WILEY-VCH Verlag © H NMR spectra of VC and PVCA in DMF-d 1 a) The digital images of PVCA-LiDFOB; b) the digital images of cellulose/PVCA-LiDFOB composite solid polymer electrolyte; c) the surface composite solid of cellulose/PVCA-LiDFOB of PVCA-LiDFOB; b) the digital images a) The digital images C for 24 h; b) FTIR spectra comparison of VC, PVCA, and VC into PVCA after heating at 60 °C for 24 h; b) FTIR spectra comparison of VC, PVCA, a) The typical image of in situ polymerization of 2016, 1600377 Sci. www.MaterialsViews.com Adv. Figure 2. morphology and d) the cross-section of cellulose/PVCA–LiDFOB composite polymer electrolyte. Figure 1. PVCA-LiDFOB; c) Full paper 1600377 lower than that of the oxygen atom in C charge ofoxygenatominC Gaussian software (showninFigure distribution oftherepeatingunitPVCAwascalculatedby bonate groupinPVCA,probabilityofelectronclouddensity sity distributionofPVCAwithLi (three repeatingunitsofPVCA)and b)Probabilityofelectroncloudden- Figure 3. interconnected channelsforlithiumionstransportation. incorporated into the voids of cellulose nonwoven, resulting in generated PVCA-LiDFOB solidpolymerelectrolyteuniformly cellulose-based Supporting Information.Moreover, theinsitu PVCA-SPE wasabout30µm,whichveryclosetothatof bonate groupinPVCA. www.advancedscience.com To furtherinvestigatetheinteractionbetweenLi (4 of9) a) Probabilityofelectronclouddensity distributionofPVCA wileyonlinelibrary.com  + ; c)possibleinteractionofLi O was–0.555,whichslightly 3a,b). Naturalbondorbital © 2016TheAuthors.Published byWILEY-VCHVerlag GmbH&Co. KGaA,Weinheim  O  C (–0.547 and + withcar + withcar- - without AIBN(1.0mgmL R istheidealgasconstant. pears or at whichconfiguration freeentropy becomeszero,and the Vogel scalingtemperatureatwhichthefreevolumedisap- –0.554), indicating that Li hindrance effect wouldprobably weaken theinteractionof Li (seen inFigure S5,Supporting Information).However, steric and Zhangetal. mechanism wasalsopreviouslydiscussedbyTominaga etal. mainly contributedtothelithiumionconductivity. Thissimilar to the number of carrier ions, where and itscapacitanceinparallel. was assignedtothebulkresistance ofthepolymerelectrolyte rent impedance spectra. The semicircle at high frequency be notedthattherearetwosemicircles inthealternatingcur tial currentvalueof32.4µAatavoltage0.05V. Itshould the currentvaluereachedaplateau of27.6µAfromtheini- the Bruce–Vincent–Evans equation.AsseenfromFigure 4b, power output.Thetransferencenumbercanbecalculatedfrom generally ahightransferencenumberisdesirableforbetter number is a critical factor regarding the ionic conductivity and uted totheeffective conductivity. Thelithiumiontransference electrode reactionandlithiumionconductivityitselfiscontrib - lithium ion battery, only lithium ionis effectively involved into of LiCoO of AIBNhadalmostnoimpactonelectrochemicalproperties the Supporting Information.Obviously, suchasmallamount curves of liquid electrolyte based LiCoO initiator for free radical polymerization. The charge/discharge Azobisisobutyronitrile (AIBN) is a very common and efficient 2.2. ElectrochemicalPropertiesofPVCA-SPE with oxygenatominC of PEObasedelectrolytewasonlyabout2.76×10 with thisLi (seen in Figure 3c). The segmental motion of the PVCA along Fulcher (VTF)empiricalequation of polymerelectrolytescanbedescribedbytheVogel–Tamman– 50 2.23 shown inFigure ionic conductivityofPVCA-SPE with1.0mgmL for thegenerationofPVCA-SPE. Thetemperature-dependent the lithiumiontransferencenumberlowerthan0.5. usually movemuchfasterthanlithiumcations,whichmakes energy barrierforlithiumiontransferinPVCA-SPE. has aloweractivationenergy(0.030eV),indicativeofthelow pared withotherkinds of polymer electrolytes, ting parametersforPVCA-SPE was shown inFigure 4a.Com- trolyte andPANbasedelectrolyte. which is higher than that of previous reported PEO based elec- σ As weknow, indualionsconductingsystem,anionsofsalt = °C. Thetemperature-dependentionicconductivitybehavior AT × 10 A isconductivitypre-exponentialfactor, whichisrelated − 1/ 2 −5 /Li batteries.So,AIBNwasadoptedastheinitiator 2 Scm ex + coupling/decouplingwithoxygenatominC p    [27,29] RT −1 () 4a. TheionicconductivityofPVCA-SPE is at25°Cand9.82×10 − E − a  T o O +    trended to interact with both of them [31,32]  −1

C, converselyfavoringofLi ) weredisplayedinFigure S6in ThecalculatedvaluesofVTFfit- E [35] a is the activation energy, Thebroadsemicircleinthe [14,30] Theionicconductivity 2 www.MaterialsViews.com /Li batteries with and −5 Scm Adv. Sci. [3] −1 −5 PVCA-SPE −1 AIBNwas 2016, 1600377 Scm at50°C, [33,34] +  O T −1  In  0 (1) at is O C + -

Full paper 1600377 , respec- −2 - . The suffi (5 of 9) −2 www.advancedscience.com , which may be due to the −2 wileyonlinelibrary.com The interfacial stability of PVCA-SPE with lithium metal had The interfacial stability of PVCA-SPE tively. The slight and synchronous voltage fluctuation could tively. at the current be observed in the deposition/striping process density of 0.05 and 0.10 mA cm fluctuation of room temperature. The over-potential gradually over-potential fluctuation of room temperature. The the forma- to be attributed may cycles time/ or with increasing surface. In addition of a favorable SEI on the lithium metal phenomenon after tion, there was no observable short circuit mA cm 600 h polarization at both 0.05 and 0.10 cient rigidity of solid state PVCA-SPE would suppress dendrite cient rigidity of solid state PVCA-SPE crossover during long-term cycle and prevent short circuit occurrence, indicating a good compatibility between PVCA-SPE and lithium anode. of the the impedance variation by analyzing also been evaluated cell for a period of 30 d (shown symmetrical Li/PVCA-SPE/Li of 5c). The alternating current impedance spectra in Figure two were There 5d. Figure in shown were cell symmetrical the to due was which spectrum, impedance the in semicircles bulk electrolyte resistance and interfacial resistance between lithium electrode and polymer electrolyte. As can be seen from 5d, no obvious variation of bulk electrolyte resistance Figure was found during the measuring process. The interfacial resistance between lithium electrode and polymer electrolyte would continually increase to some extent during the first 5 d, then The interfacial day. fifth kept quiet stable at about 1500 Ω after and lithium anode was favorable stability between PVCA-SPE ex-site PVCA-SPE for excellent cycling performance. Moreover, presented the cycling performance of symmetric Li/PVCA-SPE/ presented the cycling performance of symmetric 0.10 mA cm Li cells at a current density of 0.05 and - - - 5a,b So, the high [12,33,36] So, PVCA-SPE exhibited excellent exhibited So, PVCA-SPE 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2016 The Authors. Published by WILEY-VCH Verlag © [32] Li reaction. As can be seen from the inset = Li reaction. As can be seen from the inset

− + e

+ a)Temperature dependent ionic conductivity of PVCA-SPE; b) current variation with time during polarization of a Li/PVCA-SPE/Li symmetrical ionic conductivity of PVCA-SPE; b) current variation with time during polarization of a dependent a)Temperature 2016, 1600377 after polarization process. From Bruce–Vincent–Evans Bruce–Vincent–Evans From process. polarization after Ω Sci. at 50 °C. It corresponded to the start of oxidative decom- A wide electrochemical stability window is a critical factor The electrochemical compatibility of PVCA-SPE/Li inter The electrochemical compatibility of PVCA-SPE/Li + www.MaterialsViews.com Figure 4. Linear voltammetry curve Inset shows the AC impedance spectra of symmetrical battery. V. cell at 25 °C, with total applied potential difference of 0.05 of Li/PVCA-SPE/SS at c) 25 °C and d) 50 °C. lithium ion transference number of PVCA polymer electrolyte is beneficial for an enhanced power capability. Asym- for high performance electrolyte of high voltage battery. steel were assembled metrical cells of Li/PVCA-SPE/stainless to evaluate the electrochemical stability window of PVCA-SPE. PVCA- 4c,d presented the linear sweep voltammetry of Figure 4d, the Figure in As shown respectively. 50 °C, and at 25 SPE current density began to increase obviously at 4.5 V versus Li/ Li position of the electrolyte. Adv. medium-to-low frequency region was attributed to interfacial medium-to-low frequency region was attributed polymer electro- electrode and between lithium resistance to comprise of lyte. The interfacial resistance was considered charge-transfer resist- a surface film resistance on Li and the ance of the Li of Figure 4b, the interfacial resistance changed from 1300 to 4b, the of Figure 1370 ion transference equation, we could easily obtain the lithium higher much (0.57), electrolyte polymer PVCA of number than PEO-based polymer electrolyte (≈0.2). ther oxidation of electrolyte, which endow this solid electrolyte resulting in a better cycle per a better electrochemical stability, formance of lithium batteries. phase was estimated by monitoring the impendence trend with a long-term lithium deposition/striping cycles. Figure electrochemical stability even at the elevated temperature. The excellent solid/solid interface compatibility would prevent fur Full paper 1600377 tery deliveredreversiblecapacityofabout97mAhg and b)0.10mAcm 2.3. LiCoO improved interfacialcompatibilitywiththeelectrodes. 2 h.So,PVCA-SPE obtainedfrominsitugenerationpossessed from 3400 to 2800 the interfacialresistanceofLi/PEO-SPE/Licellwoulddecrease facial contactwithlithiumelectrode.Itwasworthnotingthat among these three polymer electrolytes, due to its poor inter Ex-site PVCA-SPE showed the highest interfacial resistance played theresultofacimpedancespectrasymmetricalcells. for comparison.Figure S7intheSupporting Informationdis- and PEO-SPEwereobtainedfromtraditionalcastingtechnique Figure 5. lithium batteries operate at room temperature, although previous lithium batteriesoperateatroom temperature,althoughprevious polymer electrolytecannotsatisfy thegeneralconditionsmaking (seen inFigure S9,Supporting Information).PEO-based solid discharge curvesofPVCA-SPE basedLiCoO Figure S9intheSupporting Informationpresentedthecharge/ teries werestoredat60° represented inFigure S8intheSupporting Information.Thebat- polymer lithiumbatteriesviaaninsitugenerationprocesswas the cathodeandLimetalasanode.Thepreparationofsolid batteries wasevaluatedbyusinghighvoltageLiCoO The electrochemical performance of the PVCA-SPE based lithium rent densityof0.1C(15mAg of Li/PVCA-SPE/Lisymmetricalcellatroomtemperature;d)ACimpedancespectracell. LiCoO PVCA-SPE andlargepolarizationat25° density of0.1C,whichwasdue tothelowionicconductivityof www.advancedscience.com (6 of9) 2 /Li cells had a lower dischargecapacityof 25 mAh g Chronopotentiometry resultsofLi/PVCA-SPE/Lisymmetricalcellsatroomtemperaturethecurrentdensitya)0.05mAcm 2 /PVCA-SPE/Li BatteryPerformances −2 wileyonlinelibrary.com for1h,respectively. Insetsshowedthemagnifiedcurvesbetween200and 220h;c)timedependenceoftheinterfacialresistance Ω when the cells were stored at 80 C for24hand80° − 1 ) at25° C. However, PEO-based C. TheLiCoO © 2016TheAuthors.Published byWILEY-VCHVerlag GmbH&Co. KGaA,Weinheim C for another 10 h. C foranother10h. 2 /Li cellsatacur − 1 at a current atacurrent 2 (4.3 V) as (4.3V)as 2 /Li bat- °C for − 1 - -

mance ofPVCA-SPE basedLiCoO cycle process,whichwasvery important forlongcycleperfor interface. Fortunately, theresistancebecomesstableafter third mation ofpassivationfilmbetweenlithiummetalandPVCA-SPE number. Theincreasedresistancemainlyderivedfromthe for of PVCA-SPE based LiCoO of firstcycle,thirdandtenthcycle.ACimpedancespectra ance ofLiCoO LiCoO the 150thcycle,dischargecapacitiesofPVCA-SPE based lombic efficiency wouldreachtoastablevalueabout99.3%.After efficiency of93.5%.After afifth charge/dischargecycle,thecou- discharge capacitywas146mAhg rent densityof0.1Cat50° capacity andanexcellentcyclingperformanceataconstantcur approaches havebeeninvestigated. PVCA-SPE basedLiCoO initial capacity(146mAhg the charge/dischargeprofiles ofLiCoO in powerbatteryisacriticalperformance. Figure 6cdepicted circuit ofPVCA-SPE basedLiCoO mation displayedtheACimpedancespectraanditsequivalent during thelong-termcycles.Figure S10intheSupporting Infor electrolyte interfacesstabilityandexcellentcyclingperformance reports. current densityofLiCoO sponding dischargecapacitywith fivecyclesperformedateach discharge currentdensitiesvaried from0.1to0.5C.Thecorre- tery withthevoltagerangeof2.5–4.3 V, whereinthecharge/ As weknow, thedurableratecapabilityofpolymerelectrolyte 2 /Li cellwas123mAhg [37] Thehighcapacityretentionindicatedgoodelectrode/ 2 /Li battery would slightly increase with the cycle /Li batterywouldslightlyincreasewiththecycle 2 2 /Li battery exhibited a high discharge /Li batteryexhibitedahighdischarge /Li batterieswasshowninFigure 6d. − C (showninFigure 1 2 ), which was similar to the previous ), whichwassimilartotheprevious /Li battery showed that the resist- − 1 , corresponding to 84.2% of the , correspondingto84.2%ofthe 2 2 /Li battery at full-charged state /Li batteryatfull-chargedstate /Li battery. [37,38] − 1 with an initial coulombic withaninitialcoulombic It was noteworthy that Itwasnoteworthythat www.MaterialsViews.com 2 /PVCA-SPE/Li bat- Adv. 6 a,b). The initial a,b). Theinitial Sci. 2016, 1600377 −2 for0.5h - - - - Full paper

1600377 C for electrode 2 (7 of 9) /Li cells using PVCA-SPE 2 www.advancedscience.com electrode and PVCA-SPE after 2 wileyonlinelibrary.com C with the voltage range of 2.5–4.3 V; 2.5–4.3 of range voltage the with °C electrode coated with PVCA-LiDFOB polymer 2 C for 10 h, the pouch type battery was charged toC for 10 h, the pouch type battery was charged electrode. 2 C. Then, the battery endured six consecutive nail pene C. Then, the battery endured six consecutive ). By a sharp contrast, the pouch type battery ). By using 8 a) The digital image of LiCoO Figure electrolyte (without cellulose). Inset was the surface SEM micrograph of pristine LiCoO disassembly; b) the cross-section SEM micrograph of LiCoO Figure 7. with PVCA-based polymer electrolyte (with cellulose); c) surface SEM micrograph of LiCoO based pouch type batteries. After heating process at 60 ° based pouch type batteries. After in 24 h and 80 ° 4.3 V at 50 ° the battery kept a goodtration tests. It is worthwhile to note that and displayed a relativeshape without any flame and explosion nail tests (seen after high voltage at 4.02 V without short circuit

2 /Li cells at 5th and 150th cycles at 50 at cycles 150th and 5th at cells /Li 2 a. SEM was SEM 7a. /Li cells at a current density of 0.1 C with the voltage range of 2.5–4.3 V according to cycles; /Li cells at a current density of 0.1 C with the voltage 2 was achieved at −1 at 0.5 C, which was Figure −1 electrode. From Figure 7b, Figure electrode. From 2 /PVCA-SPE/Li cells at varied current densities at 50 °C; d) discharge capacity of LiCoO /PVCA-SPE/Li cells at varied current densities at 2 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2016 The Authors. Published by WILEY-VCH Verlag © /PVCA-SPE/Li battery could deliver a /PVCA-SPE/Li 2 electrode (seen in Figure S11, Supporting S11, Supporting electrode (seen in Figure 2 a) The charge/discharge curves of PVCA-SPE based LiCoO based PVCA-SPE of curves charge/discharge The a) electrode with PVCA-SPE and the surface morphology and the electrode with PVCA-SPE electrode and polymer electrolyte. Some polymer elec- 2016, 1600377 2 2 Sci. Safety is a key concern for lithium batteries, especially for In order to find out the morphology changes of LiCoO of changes morphology the out find to order In www.MaterialsViews.com at varied current densities. c) charge/discharge curves of LiCoO Figure 6. Figure b) specific discharge capacity of PVCA-SPE based LiCoO b) specific discharge capacity of PVCA-SPE based Adv. 0.2 C, which was about 78% of the capacity at a rate of 0.1 C. 0.2 C, which was about 78% of the capacity the LiCoO Significantly, Information) was disassembled after in situ polymerization of Information) was disassembled after in shown was image digital its and PVCA used to investigate the microstructure of the cross-section of LiCoO electrode and PVCA-SPE, the cell with a smaller cellulose non- electrode and PVCA-SPE, woven than LiCoO A reversible discharge capacity of 114 mAh g A reversible discharge capacity of 114 mAh of PVCA-LiDFOB coated LiCoO coated of PVCA-LiDFOB trolyte was even incorporated into the porous cathodes origi- nated from the in situ polymerization of PVCA on the surface find- 7c). These or even inside of the cathode (shown in Figure ings manifested that close contact between the SPE and cathode reduction impedance for beneficial greatly be would interface and charge/discharge improvement. large energy storage equipments, such as electric vehicles and smart power grids. In order to evaluate the safety characteristics as solid batteries using PVCA-SPE the pouch type of PVCA-SPE, electrolyte were assembled. The preparation process of pouch type batteries was similar to that of traditional liquid electrolyte it could be seen that there was a compact adhesion between LiCoO due to the excellent interface compatibility between polymer due to the excellent interface compatibility analysis above, it was electrolyte and electrode. Based on the solid polymer elec- believed that PVCA would be a promising trolyte for high energy lithium batteries. reversible discharge capacity of 73 mAh g Full paper 1600377 high voltagePVCA-based solid-stateLiCoO higher energydensity(260WhKg for polymerelectrolytewhichseparated cathodeandanode.Later, the battery, wherecelluloseseparator wasadoptedasSupportingInformation Chemical ReagentCo., Ltd.).Thesolution wasinjectedinto2032lithium ≈ PVCA-SPE was onlyabout2.23×10 graphite (4.2V)batteries.Althoughtheionicconductivityof compatibility towardlithiumanodeandhigh-voltageLiCoO polymerization process,whichpossessedbothinterfacial trolyte was successfully prepared by afacile in situradical In thiswork,akindofnovelPVCA-based solidpolymerelec- 3. Conclusion SPE withoutflammable-electrolytepresentinherentsafety. prove thatpouchtypebatteryusinginsitugenerationofPVAC- drastic expansion.Theseresultswerepowerfulevidencesto conventional liquidelectrolytereleasedflameandunderwent ventional liquidelectrolyteafternailtests. as solidelectrolyteandsafetycomparisonbetweenpouchtypecellsusingPVCA-SPEcon- Figure 8. to getahomogeneousandtransparent solution(1.0 Co., Ltd.,99.9%)wasdissolved into10mLVC(EnergyChemica.,99.9%) 4. ExperimentalSection cathode (4.3VvsLi/Li decent ionicconductivityof9.82×10 date forhighenergysolidstatelithiumbatteries. lyte couldbeaverypromisingsolidpolymerelectrolytecandi - was demonstratedthatinsitugeneratedPVCAbasedelectro - ionic conductivityofPVCA-based solidpolymerelectrolyte.It ticles, copolymerizationwould be effective methodtoimprove ture, addingplasticizers,inorganicionicconductorornanopar electrochemical stabilitywindowupto4.5VversusLi/Li voltage ofLiCoO able ratecapabilityandexcellentcyclicperformance.Thehigh resented superiorcharge/dischargeperformance,consider www.advancedscience.com 9.6% (w/w)), then the solution was added 10 mg AIBN (Sinopharm 9.6% (w/w)),thenthesolutionwas added10mgAIBN(Sinopharm Synthesis ofMaterials:1.43gLiDFOB(Innochem(Beijing) Technology (8 of9) The consecutive nail penetration tests of the pouch type batteries using PVCA-SPE 2 wileyonlinelibrary.com wouldendowthelithiumionbatterieshavea + ). ThePVCA-SPE displayedasuperior −1 ) thanthepreviousLiCoO −5 Scm −5 Scm © 2016TheAuthors.Published byWILEY-VCHVerlag GmbH&Co. KGaA,Weinheim −1 2 atroomtempera- /Li batteriesrep- −1 m at50°C.The LiDFOB in VC, LiDFOBinVC, + and 2 / 2 - -

a conventional casting method, by mixing 80 wt% LiCoO scanning electronmicroscopy(HitachiS-4800at5kV). calculated byusingfollowingequation from 0.1Hzto1MHz.Theionicconductivityofpolymerelectrolytewas 300 withanACvoltageamplitudeof10mVoverthefrequencyrange between twostainlesssteel. Data wereacquired using BioLogic VSP- were determinedviaanACtechnique.Theelectrolytewassandwiched on aFourier transforminfraredspectrometer(BrukerVERTEX70). respectively, andI current and the initial interfacial resistance before polarization, from theauthor. Supporting Informationisavailable fromtheWileyOnlineLibraryor Supporting Information where at ascanningrateof1mVs tested onaLi/PVCA-SPE/stainlesssteelcellsbyimpedancespectroscopy resistance ofpolymerelectrode. area betweenelectrodeandelectrolyte,Rcorrespondstothebulk where state interfacialresistanceafterpolarizationfor10000s,respectively. radiation ( with aBruker-AXSMicrodiffractometer(D8Advance)usingCuK (NETZSCH) from–60°Cto200C.X-raydiffractiondatawascollected scanning calorimetryofPVCA-LiDFOBwasconductedonDSC200F3 PVCA-LiDFOB wascarriedoutonTG209F1Iris(NETZSCH).Differential tetramethylsilane asinternalreference.Thermogravimetricanalysisof spectra ofPVCAwererecordedonaBrukerAVANCE III600MHzwith material ontheelectrodeswasabout1.5mgcm acetylene black,and10wt%PVCA.Finally, thespecificdensityofactive PVCA-SPE wascalculatedfromBruce–Vincent–Evans equation LAND testingsystem(Wuhan LANDelectronicsCo., Ltd.)at50°C. charge/discharge tests of coin-type cells (CR2032) were conducted on σ t Li + = Electrochemical Measurements: Theionicconductivities of PVCA-SPE Cyclic voltammetryandlinearsweepofPVCA-SPEwere For cellperformancetests, theLiCoO =⋅ SR I l I ss l presentsthethicknessofpolymerelectrolyte,Siscontact o V istheappliedpolarizationvoltage,I

() () λ VI VI

= 1.5406Å).Infraredspectrameasurementswereconducted − − ss oo R R ss ss andR PVCA-SPE was0.013mgcm corresponding loadingamountofPVCA-LiDFOBin completion ofpolymerizationVC.Theultimate 24 hand80° lithium batterieswerekeptconstantlyat60° PVCA-SPE wasinvestigatedbyafieldemission disassembled togetthePVCA-SPE. fabricated. Afterheatprocess,thebatterieswere stainless steel/PVCA-SPE/stainlesssteelwere PVCA solidpolymerelectrolyte,symmetricbatteries in Figure1b).Inordertogetthemicrostructureof 10 h.AtranslucentPVCA-SPEwasprepared(shown electrolyte wasstoredat60°Cfor24hand80 panes. Then,thecellulosepaperwithVCliquid electrolyte wassandwichedinbetweentwoglass directly, apieceofcellulosepaperwithVCliquid conversion ofVCintoPVCAwasmorethan95%. respectively. The calculated polymerization and diethyletherasasolventprecipitant, reprecipitation methodusingdimethylformamide was purifiedafterthreecyclesofaredissolution–

Characterization: Themorphologyofthe In ordertoshowthepictureofPVCA-SPE ss arethesteady-statecurrentandsteady- −1 . Thelithiumiontransfernumberof C for 10 h in hot box to generate the C for10hinhotboxtogeneratethe 2 cathodewaspreparedin www.MaterialsViews.com o andR − 2 −2 . The obtained PVCA . TheobtainedPVCA Adv. . Thegalvanostatic Sci. o aretheinitial 2016, 1600377 1 H and 2 , 10 wt% C for C for 13 (3) (2) C α

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