Lithium and sodium insertion in ternary chromium oxides

LITHIUI~I AND SODIUM INSERTION EN TERNARY CltROMIUM OXIDES R. KOKSBANG, S. yDEoANDERSEN

K. WEST, B ZACHAU-CHRISTI ANSEN and g SKAtuRUP ~ 0 r~,r162 v , tmffRv of ~ . m ~ r g Dg280~ ~ , g ~ . O~mark

~thlom ~a8 sod~ami n t r ~iag p~O pol~er 9 co~. At ~ a ~ a

in MCr~a (M~LLN~ K) h~ bet. institutedby cydi~Sof L] ~fl Na ~]Is.I ~ I 2 S ' C

e~ns and by chemical~ i ~

~

~ b m h ~ n a ~ m at~

t e m ~ t a ~ Mr

m~d forf ~ h ~

tmger~tu~ tb~ aumb~r ofLi=o~a i n c a ~ f~uI= unh e x ~ s fo~ foran ~fials wni~ on1~o ~ Na

capadtum t ~ a t ~ tempmm~ is dueto a pha~ r u ~ I~ insmion.T~e *pealfieener~i~~l~t~ted f~m Oe f i ~ di~ r162 to 1.SV~ g $ U, a~ ~50, 97Sand I ] oo ~ oxidef0[LUKCr,Os,L~,Cf,Oh and L ~ t sos ~tp~v~7, and [7~ Wle~ o~id~f ~ disharget o 1.0V~r Na ofNatKCr,O,~[1~.

L Intrcr

~t~r The lithium ions ace distribmed randomly o w r all the oczahedml sites,rendering this material

S e r i a l binary e h ~ m l o m oxide~ e.g, Cr20s and

a f r a m ~ o r k st~eture rather than a layer ~ t ~ c t u ~

Cr~Os t I~1, h a w been in~stigated as active ma-

lceluts i n ~ h a ~ g e ~ l e litblumbattr of m~fials has a~trar

"l~is group

atle~fion due to high ~po-

gifie~elFjr (CrjOm: ~ 1200 WIl/kg oxide). In this l~per, ~suRs a ~ predated on l i t h i u minsettion into anotherscd~ o f c h ~ m l u moxldr MCY~O~ ( M = Li, Na, K). Thes~ ox~d~ have open stmclures as seen from their low densities (LiCraOs: 3.46 g / ~ , NaCr~Os: 3.23 # r ~, KCtaOs: 3.02 g/cma) cornpared to other r chromium oxld~, e.g. Cr~Os (5.21 gtcm~), According Io Wilhelnti [7,8] the i ~ s t r u c t m l c~pOUnds NaCrsO, and KCr~Os a~const~cted o f CI'O~ octahcdra and CrO~ tetrahedra a~anged i n l a y ~ by comer sharlng.~ r laye~ ~ held togeth~ by int~layer a]kallmetal iota coordinaledto t ~ ~ ~g9 atom~ Thv st~ r o f LiCX/~Oa|g,9] ks c1~12 ~r 1o that o f ( N g K)Cr,O~, By packingthe laye~ o f the lattercl~r theconrdinationnumbcrofthe interlayerions is ~du~:ed to fix, as i n the LiCr~Os

Structurally,the (Na, K)Cr~O~ st~ctu~ provides

p o~ibililyfor l i t h i u mdiffusionp a ~ i n two dimenmi~xygen luyr However, wlthlnthe layr and paralld to i b m , ~ r o n ~ dimensionalchannelswith d i a r a e t ~ ( ~ 1 ~ ) larger 1ban tho a v ~ g e interlayerspacing I n LiCr~O~thesa channelsa ~ the onlyd i f f ~ i ~ paths lefti n the s t ~ t ~ . I n t h e e h a n n d s , four4~oordtnatcd~ply~itcs per f o ~ u l a uaJt ~ a be id~t~fied. 10r obse~ed average e h r o m i u m ~ x y g ~ distaztces i n thr ~ t a h e d ~ and tet~hedra ~ e 2.05 and 165/~, ~stmctively,i n LiCr~Oe ~ d 1.92 aud 1.63 A in KCr~Os. The chromium-oxygendlstaaces i n oetahedra and let~hedra expected from standard ionicradil f ~ Cr(]II) and Cr(VI ) a ~ 1 96 and 1.61 A. Similarly.the lithlum-oxygendlst~ce for oet~hed~-al~ m d i n a t l o no f l lfhlum is ~ p ec~edto be 2.11 /~ [ IO]. Tnls ~s i n good agreementwhh the val~cs o b ~ M for tetrahedral~ordlnatioa in both s ~ tures and for oetaht:dral ~ o r d i n a l i o n in gCr~Os, where~ lh~ octahedml c h ~ m l m n - o x y g ~ distance ~ons between r162r

0167-2738/88/$ 03.50 9 EI~Vi ~ science Pnblishc~ B.V. (North-HollandPhysics PublishingDivision)

in LiCr~O~ is i~tr bm~ the ~lues exIx~Ctcd for Cr{III) ~d Li(I) cctahedraOy cowdl~ted to oxygen, This indi~les the pm~nce of Cr( Ill) and Cr(VI), coordinated octahedmlly and tstrahedtally~spcctively, in the compounds From tha~ obviations, and measu~ments of the ma Bnctlc svsccpt[bility o f KCr3Os [ 11 ], it is ~ncluded that oh~mium is e~ntially p~sent in lhe tdval~t a n d hexavalent oxidatio~ ~tat~ in the ratio 1 : 2. In c h ~ m i u m oxides the obse~cd oxyg#n ~oedination is tctrahedral for Cr(VI) a n d Cr(V), tetra. hedral a n d octahedml for Cr(IV) a n d oclahed~l for Cr(HI) [ 121. From a stmctu~l point o f v i ~ , i t is thcrcfo~ pusslble to r e d u ~ the tetrahedml Cr(VI) to Cr(IV), ~ponthng to insertion of four lithium pet formula unit, without changing the c h ~ m i ~ c ~ r d i nmion. Further ~duCtion o f c h ~ m i u m must lead m st~ctml b~kdo~.

fiomad FC 124) in a~tonit rile(Mc~k, analyse))~st onaninert substrate,Thethielmcssofthefilmsdrlcd in vacuum al 60~ ov~ight was 50-60 pro. Composits cathodeS, r 50~0 we% MCr~Os, 5I0 ~% Shawthlg~ black, the remaining part being (PEO)gLiCF~SO~, ~ easton Ni-foi[and dried at ] 20~C in v a ~ n m ove~ighL The thickness of the cathodes WaS ~ 50 p.m, Cells with the ~nfigumlioa Li[ (PEO)~LICF~SO~ IMCeaOs cathode ~ r e moun~ed with spring load b e r g e n Ni-platcd brass discs and housed in a scaled brass contains. The ~]ls w ~ e dlscharg~d and charged g a J ~ n ~ t a t i~lly at 125*C, or discharged potentlost atleally to a p r ~ t voHagclevel a f i ~ which the ~ t h o d r mat r w e ~ investigated b y X - ~ y a n d I R ~alysis. 3. Results and ~lisemsion

2. Ex$*eti~ntal L i C r D s , NaCraO~ a n d KCr~Os ~ e p~parcaJ as dc~rihed orllcr [7,9,13]. Mixtur~ of M~Cr20~ (M = Li. No, K, Merck analyse) and CtOs (Mc~k, ~alysc),in the molar ratio I: 2 ~ m ginned in quartz c~cibles and slowly h ~ t e d in air to 350'C, where they were k~pt for 2 h. T h e ex~ss M~Cr~O, was used to p ~ v ~ t formation of Cr~Os, one of the c h ~ m i ~ suboxid~ formed during the~al de~mpositlon of CrO~ [14-16], Hon-~cted M~Cr~O, wasextracted with distilled water. The black MCr~O~ compounds am i ~ l u b l e in water. X-ray powder patterns w e ~ in good agr~ment with litemtu~ data [ 7-9]. No t ~ r of Cr~Os or other p h ~ s w e ~ obse~ed. T h e alkali content of the ~ m p o u ~ d s ~ s determined by flame photometry ~ d the c h ~ m i u m ~ n t ~ t by atomic absorption. The analysis ~ n f i ~ e d the stoichiometricnatureofther169 [7.9,13]. The m ~ i m u m lithit,m uptake of ~he oxides at r ~ m t ~ p c m t u ~ was dctCiminod b y ~actioa with n-buthyllithi~ for two ~ e k s [ 17 ]. The products w ~ r investigated by X-my a n d IR technique. Polymer electrolyte films, with the r (PEO)~LiCF~SO~, ~ prepared f ~ m a ~lution of P E n (BDH. MW 600000) a n d LiCF~SOa (3M,

Constam c u m i n discharge a n d charge cu~cs o f LiCr~Os, NaCr~O, and KCraO~ at 125 ~ a m s h n ~ in fig. 1. It is s ~ that for NaCr~Oe a n d KCraOa the lithiuminscrtiontak~ p t a ~ a t axdrtually~nstant voltage, ~ 2.75 V for x < 2, indicating a t w ~ p h a ~

~aclion.Athigh~xvalu~(2 3. I:~spite the stmctu~l similaritiesbetween LiCraOs ~d (N~. K)Cr~Oa, the fo~er produces a qnltc diffe~nt Fffst discharge ~. Th~ plateaus a ~ obsc~r the largest existing at ~ 2,25 V in the ~ n g e 0,65 < x < Z $ . T h e fully discharged materials couId only be partially r~hargcd a n d the following di~harge o u ~ s show only Utile or no ~ b l a n ~ to t h a f l ~ t di~harge eulwes T n e ~ o b s e ~ t i o n s i n dinar e that the reaction which takes p l a ~ during the first di~hargr i n ~ l v ~ a n i~vers/ble structural change of the positivc ~ t e l i a l s . At 125~ the m ~ imum number o f lithium th~rtcd per f ~ u l a unil ~ds four for all mateoals, The specific energies calculated from the first di~harse ~ 850, 975 ~ d ] 100 Wh/kg oxide for Li/KCr ~Os. Li,qqaCr~Os a n d Li/LiCr#Os, respectivety. Disthargr of Na/KCr~Oa cells at 80~ (fig. 2). u ~ ingPEO-NaCIOa(O/Na=12)ctectm[yte, thowsthat

~ 1 ..... ,,It,

~

! L _ _ , , ...... ~

2*theta (degrees)

~0 KCr,O~

t. con~ant ~,,eat ~s:~ame a ~ c ~ s e ~a~es m v c ~ 314V. 0. I mmcm~.~r

aumbe~ a ~ i~ieat ed in Oe figure.

only one ~ d i u m is in~rted per fommla unit al potentla]s above I V ~ u s ~ d i u m . Sodium insertion t ~ I ~ d s to an i ~ r s ~ h l e st~ttural change. The specific ~ e r g y is 175 Wldkg oxide for the Na/ KCrsOs ~upl 9 Comparison o f X-ray diagrams of LiCrsO, a n d Li~LiCrsOs from potendostatlcatly disbursed r162 s h o ~ that the ~ c t i o n in~lves st~cturat b ~ a k down of the pristine material (figs. 3a a n d 3b). Furt h e ~ o r e , all X-ray diagrams of LixLiCrsOs ~[]s

Ng.2. ~ a n l cu~nl ~el~ I end 5 of N ~ ~ e a t ~ensity 25 ~Alcm~.

cell (~.C).

discharged to x - v ~ . ~ in the range O.S
~ d s t i n g e r than the C r ( l I l ) - O bonds, they have

m A / ~ z ~ s used i n bOth ehargc and discharge. Un-

hlgh~ vibrational ~tretching frequ~cies [18A9].

der the~ndhionsthe~pacitydecre~es fa~and

The p~gn~sive reductinu o f Cr(VI) to chromium i n low~ oxidationStates ~ould, therefore~ re~ult i n a gradualIowerlng o f the Cr~D vib~tlonalsttr chlv$ flequ~clcz.~ d an a ~ p t ~ made to f o l l ~ i t by meanso f i~f r a u d spcctr oseap2/. It proved dlfl~r to obtain umble spect~ of the r162 rocbcmlcallylitbiat~ r but t~e s ~ t n l m o f pure KCr30 s i s e o m ~ r c d w t h t h z o Li, taKo*,Cr,o, s s i n f i g .4 KOran, ~ n t a i n s eve very sbvrt (153 ~.} f r ~ CrY3 b ~ d i n each tctrai~edma (two per unit ~ l t ) . This bond ~ s p o n d s fomxaUy to ~ double bo~d, and the t w o . r i d s at h i g h e rG't~aencies (954 and 986 ~-I) a ~ a ~ c i a t e d with this f ~ r bone. All the other oxygen atom~ arc shared betwee~t telcaJ~edra and ocmhr m and togethert h ~ ~ m plexCr~O v l b ~ t l o m giverise t o the broad aL~o~t(on witha m a x i m u mat 8I I c m -I. On insertloar L I I ]ithlam,the weaR. eningo f the t ~ d s ~ a ~ s ~ n i n ~ d m e ~ o f the hlgh9 frequency (to ?aS r -~) and the zgpeara n ~ ~ f = absorption shoglder el ~ 700 em -I. At tins levy d ~g~ee o f ~ d u ~ i o ~ the ~ibrafio~al f r ~ queneies ate s~ill ~ n s l d e ~ b l y higherlhan i n Cr:O, (64O and 580 era-'), In fig. 5a the developmeulo f the discharge ~paetry is shown as a functiono f cyclingo f a Li/KCr~O,

cvemna]ly] e ~ l s o f f at appmximatdy one l i t h i u m !0~ Copula uliit. A Lit~'qaCr~Os~11 was recharged t o 3.8 V (fig. 5b ). The initiale.~pacity was the ~ m e as hi the p ~ o u s experiment(fig. 5a). H o ~ e r , up to 85% o f the inltial ~ p a c i l y w ~ ~ d despite the inefficient charge o f the ceil ~ u s e d by the r 1 6 2 instabilJr/oftheelectrolyte at t h e ~ r k i n g t ~ u p e v aturc [201. Morn t h ~ 50~ o f the i n i ~ l capacity ~ s retained after ~0 ot~lcs, ~ c s ~ n d i n g to a Slg~fic energyo f = ~fl0 VcWkg.

eellbetweenlS~d3.4V.

Aco~md~gltyofOA

4. C ~ d n s i o n It h ~ b ~ s h o ~ that the ~ x l m u m flumbefo f l i t h i u min~rted per Copula unit c x ~ d s four for MCr~O~( M = L i , No, K~ a t 125~C, whiteonly one I i ~ u m i s i l ~ e d I:~ KC-raC*~at ~oom temperature M m a r i o n with n - b m b y l l l t h i ~ . The discharge c o ~ show that l i t h i u minsertiona t elevated t0m!eemlore prone ads a~ tw~pi~a~ reactions, l ' h e p h ~ transitioni s i ~ v e ~ i b l e and the n ~ pha*e: f o x e d i* able to a ~ m m o d a t e m o ~ l i t h i u mthan the pri~ tlne matefialgIt i~ f n r t h e ~ o m believedto be stmerurallydifferentalthoughi l has h ~ n impo~ible to

Fig.4. Infrared~pec~ t a~v~ti~ peaksd o ~ r a s ) in the C r ~ str~tchingrr U, ,,r~,,c~,o ....

~

KCr30~ (~pp~ tm~} ~m~a~d ~th

Dr, Kjr R ~ m u s ~ n ~ d BodilF ] [ ~ o f the T~hnicalUni~rs~tyo f D c n ~ r k a ~ t h ~ k e d for h d p i nE ~ t h the infraredm~sulerncnts, o

Io

~

~0

,u

so

[I 1J o ~ B h s r 4 ~ d I~ SchSIIho~,LE l ~ t ~ e m g ~ 1~4

!t

:

I~k~6 (Iq82) 2t$ .........

FiE, 5. Di~amc capaci~ ~c~us number or c~1r [or (a) Li/ K C r ~ . [.5-~.4 V and 0+2$ ~ c m ' : ~ ] L i ~ a ~ , O , for ~ i c h

idr

~h~ pheac(s), S O ~ O1"the i~setled ]ithlum

ions 8r tlg~tIy 10ou~~ ~ d ~ o t

bg remove~[ ~ r 1 6 2

~t pog~n6al~ ~bovu 3,6 v vc~u~ lithium,| { ~ r recto than ~0% o f the initialcapacity was retainer a~et 50 cycle. Di~hargco f a Na/KCr~Os cell at 80~ shown that only one sodiumper formulaunit ~ n be i~crted at pot~tials above I V v e n u s ~ d u m . Sodium i n ~ t~oa also l ~ d s to i ~ v e r s i b l e slmcturalchanges. The sp~ifle cnerg[~ Calculated f ~ m the f i ~ t di~ ch~trg~~ w e s to 1.5 V vo~ns l i t h i u mare 8~0. 975 and l ] 00 Wh/kg oxide for LI/KCr~O~, Li/?4aCrlO~ ~ d Lb'LiCr'Oa. resp~clivclY, and 175 wh/~g oxido for d2~harge to I V v e ~ s sodium o f Na/KCrjO~ oils.

[51Y. Takcdr ~ ~ n n ~ Y.T~jJ and O. Ynmamol~ J. ~ I~hcm, S ~ ] 31 (, 984) 2~6.

[9~~-A W ~ d m i , ~ v K~i~6 ([S~) I~L [ ~~ R-D- ~ ~ 1 7 6 AV~ ~

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[ i l l w ~ e ~ m , Z ~ o ~ ~ l ~ m Chem. 301 (19~q) 32~ 112~A.F-Wells,5 ' ~ i~o~nic ~h~isc~. ~th ~ . q~arr prr O~rorr 1984) ~ 1197" [I a ] L. Suchow.t. ~nkuchen ann R, wa~l,1. Am.~ m . Soe. 74 ( 19~211678 [i 4] R S Schwartz,I. Fa~kuchen~ d R. W~d, J, Am. ~em. soc. 74 it9~21167~, [ I~] ~-A. Wilh~l~i,AclnChem.Senna.22 {t96~) 2~ 5. [ 171M.~ , in:~ t ~onI ~ a ~ 1 ; ~ ~, ~, vl~ Cool (Nonl~Hollana, ~s~rdam, L973)pp. 66S-673. [ Is l C,G,Ba~*:1o~. L ~wls ~ R.S.Nyholm,J. ~em. S~, (1959)3S52 [19]j j. F~I~I1~6A~ ~n~blZAU~lr~l~j . ~ c ~ ~ {199~) 21~ [~0] M,$ Amznd,SOlidS(alrIoni~ 9/10(1983)745