- Email: [email protected]
Solid electrolyte battery research within the EEC research programme on energy conservation
Solid State Ionics 5 (1981)9 14
North-HollandPublishingCompany
SOLID ELECTROLYTE BATTERY RESEARCH WITHIN THE RESEARCH PROGRAMME ON ENERGY CONSERVATION J.
EEC
JENSEN
Energy Research Laboratory Odense University, Campusvej 5230 O d e n s e M, D e n m a r k
55
Traditionally E u r o p e a n b a t t e r y R & D has b e e n t a k e n c a r e of by the b a t t e r y i n d u s t r y i t s e l f . In r e c e n t y e a r s a r a t h e r s u d d e n i n c r e a s e in r e s e a r c h involving universities and s c i e n t i f i c l a b o r a t o r i e s h a s t a k e n p l a c e in the f i e l d of s e c o n d a r y b a t t e r i e s . The a p p e a r a n c e of a r a n g e of c o m p l e t e ly n e w i d e a s for a d v a n c e d b a t t e r i e s i n s p i r e d the E u r o p e a n C o m m u n i t y (EC) to set up a b a t t e r y r e s e a r c h p r o g r a m m e in 1976. F i v e o u t of six p r o j e c t s have been covering solid electrolyte r e s e a r c h . The l a r g e s t b a s i c r e s e a r c h p r o j e c t c o n t r a c t e d by the EC w a s the A n g l o / D a n i s h p r o j e c t "Mat e r i a l s R e s e a r c h for A d v a n c e d B a t t e r i e s " s t a r t e d in 1978 at s e v e r a l laboratories in the UK and D e n m a r k .
1.
INTRODUCTION
S i n c e the d i s c o v e r y of v e r y h i g h s o d i u m ion m o b i l i t y in s o d i u m b e t a - a l u m i n a by W e b e r and K u m m e r at the F o r d M o t o r C o m pany fifteen years ago many research programmes t h r o u g h o u t the w o r l d w e r e set in m o t i o n to d e v e l o p s o d i u m - s u l p h u r batteries. In E u r o p e the l a r g e s t i n v e s t m e n t s in R & D h a v e b e e n m a d e in the UK f o l l o w e d by G e r m a n y and F r a n c e . The w o r k has b e e n f i n a n c e d by n a t i o n a l g o v e r n m e n t s and by i n d u s t r y (UK : C h l o r i d e , G e r m a n y : B B C and F r a n c e : C G E ) , and scientific laboratories s u c h as Ilarwell, UK and B a t t e l l e , G e r m a n y h a v e b e e n involved. Simultaneously w i t h the w o r k on N a - S battery development in the e a r l y s e v e n ties, m a n y r e s e a r c h c e n t e r s and u n i v e r sity laboratories in E u r o p e s t a r t e d p r o g r a m m e s to try to d i s c o v e r new f a s t ion conducting solid electrolyte materials. T h e s u c c e s s of t h e s e p r o g r a m m e s together w i t h the c o n c e p t of the i n s e r t i o n c o m p o u n d or s o l i d s o l u t i o n e l e c t r o d e f i r s t o u t l i n e d by S t e e l e at I m p e r i a l C o l l e g e , L o n d o n and W h i t t i n g h a m at E x x o n , USA, m a d e the a p p e a r a n c e of a r a n g e of new i d e a s for a d v a n c e d b a t t e r i e s p o s s i b l e in the m i d s e v e n t i e s . T h i s b r o u g h t a b o u t the EC and n a t i o n a l p u b l i c f u n d s for r a t h e r f u n d a m e n t a l r e s e a r c h in s e v e r a l ~European c o u n t r i e s . 2.
TIIE EC A D V A N C E D
BATTERY
RESEARCH
The EC b a t t e r y r e s e a r c h p r o g r a m m e c l u d e two m a i n t y p e s of b a t t e r i e s solid electrolytes, namely :
inwith
a)
liquid/solid/liquid
b)
solid/solid/solid
The f i r s t EC c o n t r a c t in f o r c e s i n c e J a n u a r y , 1976 w a s c o n c l u d e d w i t h the R e s e a r c h C e n t r e at M a r c o u s s i s of the Compagnie G6n6rale d'E]ectricit6, France T h e p r o j e c t r e l a t e d to t y p e a) and ent i t l e d " O p t i m i z a t i o n of b e t a - a l u m i n a as solid electrolyte for N a - S b a t t e r i e s " had the a i m to s t u d y and to s o l v e the technological and e c o n o m i c p r o b l e m s in the d e v e l o p m e n t and i n d u s t r i a l p r o d u c t ion of a b e t a - a l u m i n a electrolyte for a b a t t e r y of 242 Ah. A l a r g e n u m b e r of methods was investigated to find the most satisfactory s t a r t i n g m a t e r i a l , and a m i x t u r e of b e t a - a l u m i n a s o b t a i n e d by f u s i o n and by s o l i d s t a t e r e a c t i o n w a s f o u n d to be the b e s t one. P r e p a r a t i o n of the g r e e n t u b e by e l e c t r o p h o r e t i c depos i t i o n of the p o w d e r w a s f o u n d to l e a d to a v e r y u n i f o r m tube. In 1 9 7 8 t h r e e s m a l l EC c o n t r a c t s on exp l o r a t o r y r e s e a r c h w e r e s i g n e d w i t h the French universities at B o r d e a u x , N a n t e s and R e n n e s . At B o r d e a u x (Hagenm~ller) s y n t h e s i s and c h a r a c t e r i z a t i o n of n e w solid lithium electrolytes was carried out. G l a s s e s f o r m e d f r o m the c o m p o n e n t s B203-LiO2-LiCI were investigated. The p r o j e c t w h i c h is p a r t of the new EC p r o g r a m m e ( s t a r t e d in 1980) s h o w e d p r o m i s ing r e s u l t s . At N a n t e s (Rouxel) the r e s e a r c h w a s f o c u s e d on the d e v e l o p m e n t of new e l e c t r o d e m a t e r i a l s b a s e d on lithium intercalation, and Rennes (Lucas) d i d a s t u d y on n e w e l e c t r o l y t e m a t e r i a l s w i t h f l u o r i d e ion c o n d u c t i o n .
0 167 2738/81/0000 0000/$02.75 © North-Holland Publishing Company
J. Jensen / Solid electrolyte battery research within the EEC
10
These rather small p r o j e c t s were c l o s e l y linked to the l a r g e s t basic r e s e a r c h ECproject -the A n g l o / D a n i s h p r o j e c t entitled " M a t e r i a l s R e s e a r c h for A d v a n c e d B a t t e r i e s " . T h e r e has been a f r e q u e n t i n f o r m a t i o n e x c h a n g e b e t w e e n the r e s e a r c h g r o u p s of all these four p r o j e c t s thus l e a d i n g to an A n g l o / D a n i s h / French c o l l a b o r a t i o n .
The most i m p o r t a n t e x p e r i m e n t a l result was the d e v e l o p m e n t of new p r e p a r a t i v e t e c h n i q u e s r e l a t e d to hydrogen-do~)ed Li3N " Single c r y s t a l s were g r o w n by the C z o c h r a l s k i m e t h o d (Figure ]) •
The A n g l o / D a n i s h p r o j e c t began in J a n u a r y 1978 and c o n t i n u e d until M a r c h 1980. The p r o j e c t involved seven p a r t i c i p a t i n g laboratories, four in B r i t a i n (at AERE, Harwell} Leeds U n i v e r s i t y ; I m p e r i a l College, L o n d o n and O x f o r d University) and three in D e n m a r k (at O d e n s e U n i v e r sity; the D a n i s h T e c h n i c a l U n i v e r s i t y , L y n g b y and R i s e N a t i o n a l L a b o r a t o r y ) . The EC, who paid half of the cost of the r e s e a r c h from its E n e r g y C o n s e r v a t i o n p r o g r a m m e , p l a c e d separate c o n t r a c t s with H a r w e l l in the UK and O d e n s e U n i v e r s i t y in Denmark. The aim of the p r o j e c t w h i c h has r i g h t l y been d e s c r i b e d as "A N e w E x p e r i m e n t in S c i e n c e and T e c h n o l o g y " [i] has been to d e v e l o p and c h a r a c t e r i z e m a t e r i a l s for second g e n e r a t i o n advanced, r e c h a r g e a b l e (secondary) b a t t e r i e s and to i d e n t i f y m a t e r i a l s and cell types most p r o m i s i n g for further d e v e l o p m e n t . A p r o g r e s s overv i e w c o v e r i n g m a t e r i a l s r e s e a r c h [2] and a p p l i c a t i o n s t u d i e s [3] is g i v e n in the following. 3.
ADVANCED
SOLID
ELECTROLYTES
The e v a l u a t i o n of l i t h i u m halide based composite electrolytes reproduced earlier work d e m o n s t r a t i n g the e n h a n c e m e n t of ionic c o n d u c t i v i t y a c h i e v a b l e by d i s p e r sion of the halide in a v e r y - f i n e l y - d i v i ded alumina. S e v e r a l likely m e c h a n i s m s were revealed, d e p e n d i n g on the t e m p e r a ture, the salt used and the humidity, but all were d e p e n d e n t on i n t e r r a c i a l g r a i n - b o u n d a r y c o n d u c t i o n processes. The p o s s i b l e role of water or h y d r o x i d e cannot be d i s c o u n t e d in work with very h y g r o s c o p i c c o m p o u n d s such as LiI and LiCl. A theoretical sub-project demonstrated the d i f f i c u l t i e s of c o m p u t e r s i m u l a t i o n of o x y g e n - i o n c o n d u c t o r s w h e r e all interatomic p o t e n t i a l s are not very well known. In c o n t r a s t the work on b e t a - a l u m i n a and l i t h i u m n i t r i d e r e v e a l e d the u t i l i t y of m o l e c u l a r d y n a m i c s c a l c u l a t ions w h e r e p o t e n t i a l s and atom p o s i t i o n s are well e s t a b l i s h e d . For Li3N the high ionic c o n d u c t i v i t y was shown to be the result of h i g h l y m o b i l e l i t h i u m vacancies.
Figure
Source
1
Top : C z o c h r a l s k i - g r o w n L i 3 N boule w i t h c y l i n d r i c a l section about 15 mm diameter. B o t t o m : Single c r y s t a l slice 1.5 mm thick. Length al out i 0 mm : Ref. 2 (DTH, Denmark)
The c o n d u c t i v i t y of the o p t i m u m d o p e d c r y s t a l at room t e m p e r a t u r e is very high (6.10-3 ohm -I cm-l) , a factor of two higher than p r e v i o u s l y a c h i e v e d elsewhere. In Figure 2 the effect <)i h y d r o g e n dopant level is shown. The h i g h e s t c o n d u c t i v i t y was o b s e r v e d wilen doping with 0.5 atomic % hydrogen. P o l y c r y s t a l l i n e m a t e r i a l has ~)een mado by m e l t i n g and fast cooling. The samL~les w h i c h have good m e c h a n i c a l pro<~erties have a c o n d u c t i v i t y of 2-3-10 -° ohm -I cm -I at room t e m p e r a t u r e .
J. Jensen / Solid electrolyte battery research within the EEC
11
Z,,5 2"01 LOG r.T LI3N:H.~ AC - coxoucv,v i Tv
40
L,xCOO2
1.0 Celt EMF (voltS)
LixNIO 2
35"
_i
30
)
I
I
I
02
0'4
0'6
0"8
x
25
30
3,5
Figure
3
Source
: Ref.
In
1.0
L,xMO 2
Open-circuit voltages f u n c t i o n of x for the
'
as a cells
LixCoO2/Li, LixNiO2/Li Figure
Source
2
Ionic conductivity of L i 3 N crystals with varying amounts of h y d r o g e n . H y d r o g e n d o p a n t l e v e l i n c r e a s e s in the o r d e r L-25
T h e a p p l i c a t i o n of l i t h i u m n i t r i d e as an electrolyte in r e c h a r g e a b l e batteries w i l l n o w d e p e n d on the a b i l i t y to f a b r i cate thin ceramic material successfully and the d e g r e e to w h i c h the l o w d e c o m p o s i t i o n p o t e n t i a l c a n be k i n e t i c a l l y h i n d e r e d o v e r the l i f e t i m e of a cell. 4.
INSERTION
ELECTRODES
2
(Oxford,
U.,
U.K°)
42
o > 39 J 38 37 36
,
0.5
016
~
,
,
i x ,n L, Co02
07
08
09
~0
i 07
' 08
! 09
' 10
~.~ l.O 3,9
The c o n c e p t of p r e p a r a t i o n of n e w i n s e r t i o n e l e c t r o d e s by e l e c t r o l y t i c e x t r a c t i o n of m o b i l e i o n s f r o m a h o s t m a t r i x at low t e m p e r a t u r e s h a s b e e n studied. Layered metallic oxides AxMO 2 (0
38
' 05
0'6
42 ¸ &.1 •
40' 3.9 38 37 36 05
Figure 4 Source
o6 o7 &8 o9 Cell-voltage versus ion x for L i x C o O 2 / L i current densities : Ref. 2 (Oxford, U.,
i0 compositat v a r i o u s U.K.)
J. Jensen / SolM electro!rte batte
12
The E x x o n c o m p o u n d TiS 2 has b e e n e v a l u a ted u s i n g p o l y e t h y l e n e - o x i d e (PEO)-based c o m p o s i t e as e l e c t r o l y t e m a t e r i a l . The room temperature free-energy/composition c u r v e of L i x T i S 2 s t o i c h i o m e t r i c in s u l p h u r w a s c o n f i r m e d by e x t r a p o l a t i o n from d a t a c o l l e c t e d b e t w e e n 6 0 O c and 120°C ( F i g u r e 5).
i
Slice of I Lithium m e t a l ~ (~O.5mm fhick ~ 6mm diam.)
2.8
=¢~
?
i , i 1~0 pieces of PEO[LiCF3SO3) electrolyte l ~ 50#m thick~ lOmm diam) Folycrystalline pellet of 1"iSz ( ~ 5 m m thick; 6turn diam.)
2"4 Whitfingam, Steele results a tlene29c~o~KOrmfe
2.2
2"0
I I'~ I I.~
t
0 Extrapolated data using PEO electrolyte This work
o
o12
o'.4
o!6
o'.8
~'.o
1!2
X in LixTiS2
Figure Source
5
Open-circuit voltage versus x in L i x T i S 2 : Ref. 2 ( I m p e r i a l C o l l e g e , U.K.)
P r e v i o u s d a t a on L i x T i S 2 h a v e b e e n a s s e s sed and electrochemical studies indic a t e the p r e s e n c e of a c h a r g e - t r a n s f e r r e s i s t a n c e for l i t h i u m e x c h a n g e a c r o s s a liquid electrolyte/TiS 2 interface, p r o b a b l y a r i s i n g f r o m s o l v a t i o n of the l i t h i u m ion in the e l e c t r o l y t e . Transport data measurements using a solid electrolyte t e n d to c o n f i r m the c h a n g e in Li + m o b i l i t y , i n d i c a t i n g t h a t coi n t r o d u c t i o n of s o l v e n t into the TiS 2 lattice from a liquid electrolyte cannot be d i s c o u n t e d . F u r t h e r w o r k is n e e d e d to a c c u m u l a t e d a t a on Li + t r a n s p o r t in T i S ~ , these data being partlcularly important in the p o r o u s c a t h o d e and a l l - s o l i d state cell-modelling w o r k w h i c h has just been started. I n i t i a l w o r k on Cu + c o n d u c t i n g m a t e r i a l s demonstrated that ion-transport across a solid electrolyte/solid electrode interf a c e is a l m o s t s o l e l y c o n t r o l l e d b y m a s s
t r a n s p o r t w i t h the e f f e c t of c h a r g e transfer overpotential processes being negligible. A n u m b e r of i n s e r t i o n c a t h o d e m a t e r i a l s have been investigated and a s e a r c h for insertion anodes with suitable voltages w i t h r e s p e c t to m e t a l l i c l i t h i u m has been started. 5.
APf:LICATION
AND
ASSESSMENT
STUDY
A comprehensive r e v i e w has b e e n m a d e in Sub-Project IV of the role w h i c h a d v a n ced b a t t e r i e s c a n p l a y in E u r o p e earl}, in the 2 1 s t c e n t u r y . The r e s u l t s oC the application s t u d y w e r e p u b l i s h e d as a monograph [3], and a c o n f e r e n c e to d i s c u s s the c o n c l u s i o n s w i t h i n t e r e s t e d p a r t i e s f r o m a~l m e m b e r s t a t e s o f the E u r o p e a n C o m m u n i t y w a s o r g a n i s e d by DG XII in d a n u a r y 1979. It w a s c o n c l u d e d that batteries could play a significant role in d i v e r s i f y i n g the fuel b a s e of t r a n s p o r t by f a c i l i t a t i n g the i n t r o d u c t ion of e l e c t r i c v e h i c l e s , in c o n s e r v i n g energy, particularly in c o m p a r i s o n w i t h synthesizing p e t r o l e u m f r o m coal, in facilitating the o p e r a t i o n s of the e l e c tric u t i l i t i e s , e s p e c i a l l y by local storage of d i s t r i b u t e d e l e c t r i c i t y at: l o a d c e n t r e s , and by p r o v i d i n g a s t o r a g e c o m p o n e n t for s o l a r and w i n d - g e n e r a t e < ! electricity at r e m o t e sites. The d e v e l o p m e n t of a versatile, longlife, l o w - c o s t s e c o n d a r y b a t t e r y is a cornerstone For future progress i n t>oth electric transport and stationary energy storage. An d s s e s s m o n t of systems currently under engineering development ibr traction purposes shows that all of these carry a significant uncertainty of s u c c e s s , b o t h for r e n e w a b l e en©rq'/ s t o r a g e and for t r a c t i o n [>urposes an all-solid-state a l k d l i hera] b a t t e r y £s s e e n as a v e r y a t t r a c t i v e c o n c e p t for future development, it w a s a l s o s h o w n that it is p r i m a r i l y for ~ o v e r n m e n t s to j u d g e the m o s t a p p r o p r i a t e s c a l e ell e l e c t r i c v e h i c l e use and to take up n e c e s s a r y o p t i o n s to hell> i,ring u})out their introduction. Electric vehicles are s e e n as the m a j o r E u r o p e a n m a r k e t for a d v a n c e d , r e c h a r g e a b l e batteries. F u r t h e r a s s e s s m e n t s t u d i e s w e r e rec()mm e n d e d to e x p l o r e the i m p l i c a t i o n s (>f introducing significant n u n b e r s of e l e c t r i c v e h i c l e s in E u r o p e and to h e l p d r a w up a T a r g e t e d C o m m u n i t y Plun for a c t i o n . T h e s e a s s e s s m e n t s t u d i e s sh<)uld be c a r r i e d o u t in p a r a l l e l w i t h c o n t i n u i n g R&D work. 6 The
FLNAL REMARKS ,,~nglo/ban, ish
~rojoct
"Materials
J. Jensen / Solid electrolyte battery research within the EEC
R e s e a r c h for A d v a n c e d B a t t e r i e s " and other E C - r e s e a r c h p r o j e c t s have been c o n c e r n e d with c h a r a c t e r i z a t i o n and dev e l o p m e n t of m a t e r i a l s s u i t a b l e for inc o r p o r a t i o n in a d v a n c e d solid or quasisolid batteries. An E C - c o n t r a c t has r e c e n t l y been signed r e g a r d i n g a new Anglo/Danish project "Advanced Battery D e v e l o p m e n t " . This two-year p r o j e c t (Sept. 1980 - Aug. 1982) will c o n c e n trate m a i n l y on e l e c t r o c h e m i c a l studies and cell design. It is intended to e s t a b l i s h c o n t a c t s with E u r o p e a n industry in order to f a c i l i t a t e the transfer of s c i e n t i f i c r e s u l t s to p r o m o t e engineering d e v e l o p m e n t and future m a n u f a c t ure of a d v a n c e d batteries. ACKNOWLEDGEMENTS The author w i s h e s to a d k n o w l e d g e d i s c u s sions with a number of c o l l e a g u e s w i t h i n the EC E n e r g y C o n s e r v a t i o n R e s e a r c h Programme, in p a r t i c u l a r Prof. J.A.A. Ketelaar, N e t h e r l a n d s and Drs. R.M. Dell and B.C. Tofield, UK. S u p p o r t for this work was o b t a i n e d from E C - c o n t r a c t E E / E 2 / 4 2 9 / 8 0 / D K / H ahd the D a n i s h D e p a r t m e n t of Energy.
REFERENCES
13
:
[i] Tofield, B.C.; Dell, R.M. and Jensen, J. ~ A d v a n c e d B a t t e r i e s , Nature, vol. 276, No. 5685 (1978) 2]7-220 [2] T o f i e l d , B.C. ; R.M., M a t e r i a l s ced B a t t e r i e s , for the Period 31 M a r c h 1980. G 2109 (1981) [3]
Jensen, J. and Dell, R e s e a r c h for A d v a n Final S u m m a r y R e p o r t 1 J a n u a r y 1978 to AERE H a r w e l l Report 1-22
Jensen, J.; M c G e e h i n , P. and Dell, R.M., E l e c t r i c B a t t e r i e s for E n e r g y S t o r a g e and C o n s e r v a t i o n - an applic a t i o n study, O d e n s e U n i v e r s i t y (1979) 1-225
North-HollandPublishingCompany
SOLID ELECTROLYTE BATTERY RESEARCH WITHIN THE RESEARCH PROGRAMME ON ENERGY CONSERVATION J.
EEC
JENSEN
Energy Research Laboratory Odense University, Campusvej 5230 O d e n s e M, D e n m a r k
55
Traditionally E u r o p e a n b a t t e r y R & D has b e e n t a k e n c a r e of by the b a t t e r y i n d u s t r y i t s e l f . In r e c e n t y e a r s a r a t h e r s u d d e n i n c r e a s e in r e s e a r c h involving universities and s c i e n t i f i c l a b o r a t o r i e s h a s t a k e n p l a c e in the f i e l d of s e c o n d a r y b a t t e r i e s . The a p p e a r a n c e of a r a n g e of c o m p l e t e ly n e w i d e a s for a d v a n c e d b a t t e r i e s i n s p i r e d the E u r o p e a n C o m m u n i t y (EC) to set up a b a t t e r y r e s e a r c h p r o g r a m m e in 1976. F i v e o u t of six p r o j e c t s have been covering solid electrolyte r e s e a r c h . The l a r g e s t b a s i c r e s e a r c h p r o j e c t c o n t r a c t e d by the EC w a s the A n g l o / D a n i s h p r o j e c t "Mat e r i a l s R e s e a r c h for A d v a n c e d B a t t e r i e s " s t a r t e d in 1978 at s e v e r a l laboratories in the UK and D e n m a r k .
1.
INTRODUCTION
S i n c e the d i s c o v e r y of v e r y h i g h s o d i u m ion m o b i l i t y in s o d i u m b e t a - a l u m i n a by W e b e r and K u m m e r at the F o r d M o t o r C o m pany fifteen years ago many research programmes t h r o u g h o u t the w o r l d w e r e set in m o t i o n to d e v e l o p s o d i u m - s u l p h u r batteries. In E u r o p e the l a r g e s t i n v e s t m e n t s in R & D h a v e b e e n m a d e in the UK f o l l o w e d by G e r m a n y and F r a n c e . The w o r k has b e e n f i n a n c e d by n a t i o n a l g o v e r n m e n t s and by i n d u s t r y (UK : C h l o r i d e , G e r m a n y : B B C and F r a n c e : C G E ) , and scientific laboratories s u c h as Ilarwell, UK and B a t t e l l e , G e r m a n y h a v e b e e n involved. Simultaneously w i t h the w o r k on N a - S battery development in the e a r l y s e v e n ties, m a n y r e s e a r c h c e n t e r s and u n i v e r sity laboratories in E u r o p e s t a r t e d p r o g r a m m e s to try to d i s c o v e r new f a s t ion conducting solid electrolyte materials. T h e s u c c e s s of t h e s e p r o g r a m m e s together w i t h the c o n c e p t of the i n s e r t i o n c o m p o u n d or s o l i d s o l u t i o n e l e c t r o d e f i r s t o u t l i n e d by S t e e l e at I m p e r i a l C o l l e g e , L o n d o n and W h i t t i n g h a m at E x x o n , USA, m a d e the a p p e a r a n c e of a r a n g e of new i d e a s for a d v a n c e d b a t t e r i e s p o s s i b l e in the m i d s e v e n t i e s . T h i s b r o u g h t a b o u t the EC and n a t i o n a l p u b l i c f u n d s for r a t h e r f u n d a m e n t a l r e s e a r c h in s e v e r a l ~European c o u n t r i e s . 2.
TIIE EC A D V A N C E D
BATTERY
RESEARCH
The EC b a t t e r y r e s e a r c h p r o g r a m m e c l u d e two m a i n t y p e s of b a t t e r i e s solid electrolytes, namely :
inwith
a)
liquid/solid/liquid
b)
solid/solid/solid
The f i r s t EC c o n t r a c t in f o r c e s i n c e J a n u a r y , 1976 w a s c o n c l u d e d w i t h the R e s e a r c h C e n t r e at M a r c o u s s i s of the Compagnie G6n6rale d'E]ectricit6, France T h e p r o j e c t r e l a t e d to t y p e a) and ent i t l e d " O p t i m i z a t i o n of b e t a - a l u m i n a as solid electrolyte for N a - S b a t t e r i e s " had the a i m to s t u d y and to s o l v e the technological and e c o n o m i c p r o b l e m s in the d e v e l o p m e n t and i n d u s t r i a l p r o d u c t ion of a b e t a - a l u m i n a electrolyte for a b a t t e r y of 242 Ah. A l a r g e n u m b e r of methods was investigated to find the most satisfactory s t a r t i n g m a t e r i a l , and a m i x t u r e of b e t a - a l u m i n a s o b t a i n e d by f u s i o n and by s o l i d s t a t e r e a c t i o n w a s f o u n d to be the b e s t one. P r e p a r a t i o n of the g r e e n t u b e by e l e c t r o p h o r e t i c depos i t i o n of the p o w d e r w a s f o u n d to l e a d to a v e r y u n i f o r m tube. In 1 9 7 8 t h r e e s m a l l EC c o n t r a c t s on exp l o r a t o r y r e s e a r c h w e r e s i g n e d w i t h the French universities at B o r d e a u x , N a n t e s and R e n n e s . At B o r d e a u x (Hagenm~ller) s y n t h e s i s and c h a r a c t e r i z a t i o n of n e w solid lithium electrolytes was carried out. G l a s s e s f o r m e d f r o m the c o m p o n e n t s B203-LiO2-LiCI were investigated. The p r o j e c t w h i c h is p a r t of the new EC p r o g r a m m e ( s t a r t e d in 1980) s h o w e d p r o m i s ing r e s u l t s . At N a n t e s (Rouxel) the r e s e a r c h w a s f o c u s e d on the d e v e l o p m e n t of new e l e c t r o d e m a t e r i a l s b a s e d on lithium intercalation, and Rennes (Lucas) d i d a s t u d y on n e w e l e c t r o l y t e m a t e r i a l s w i t h f l u o r i d e ion c o n d u c t i o n .
0 167 2738/81/0000 0000/$02.75 © North-Holland Publishing Company
J. Jensen / Solid electrolyte battery research within the EEC
10
These rather small p r o j e c t s were c l o s e l y linked to the l a r g e s t basic r e s e a r c h ECproject -the A n g l o / D a n i s h p r o j e c t entitled " M a t e r i a l s R e s e a r c h for A d v a n c e d B a t t e r i e s " . T h e r e has been a f r e q u e n t i n f o r m a t i o n e x c h a n g e b e t w e e n the r e s e a r c h g r o u p s of all these four p r o j e c t s thus l e a d i n g to an A n g l o / D a n i s h / French c o l l a b o r a t i o n .
The most i m p o r t a n t e x p e r i m e n t a l result was the d e v e l o p m e n t of new p r e p a r a t i v e t e c h n i q u e s r e l a t e d to hydrogen-do~)ed Li3N " Single c r y s t a l s were g r o w n by the C z o c h r a l s k i m e t h o d (Figure ]) •
The A n g l o / D a n i s h p r o j e c t began in J a n u a r y 1978 and c o n t i n u e d until M a r c h 1980. The p r o j e c t involved seven p a r t i c i p a t i n g laboratories, four in B r i t a i n (at AERE, Harwell} Leeds U n i v e r s i t y ; I m p e r i a l College, L o n d o n and O x f o r d University) and three in D e n m a r k (at O d e n s e U n i v e r sity; the D a n i s h T e c h n i c a l U n i v e r s i t y , L y n g b y and R i s e N a t i o n a l L a b o r a t o r y ) . The EC, who paid half of the cost of the r e s e a r c h from its E n e r g y C o n s e r v a t i o n p r o g r a m m e , p l a c e d separate c o n t r a c t s with H a r w e l l in the UK and O d e n s e U n i v e r s i t y in Denmark. The aim of the p r o j e c t w h i c h has r i g h t l y been d e s c r i b e d as "A N e w E x p e r i m e n t in S c i e n c e and T e c h n o l o g y " [i] has been to d e v e l o p and c h a r a c t e r i z e m a t e r i a l s for second g e n e r a t i o n advanced, r e c h a r g e a b l e (secondary) b a t t e r i e s and to i d e n t i f y m a t e r i a l s and cell types most p r o m i s i n g for further d e v e l o p m e n t . A p r o g r e s s overv i e w c o v e r i n g m a t e r i a l s r e s e a r c h [2] and a p p l i c a t i o n s t u d i e s [3] is g i v e n in the following. 3.
ADVANCED
SOLID
ELECTROLYTES
The e v a l u a t i o n of l i t h i u m halide based composite electrolytes reproduced earlier work d e m o n s t r a t i n g the e n h a n c e m e n t of ionic c o n d u c t i v i t y a c h i e v a b l e by d i s p e r sion of the halide in a v e r y - f i n e l y - d i v i ded alumina. S e v e r a l likely m e c h a n i s m s were revealed, d e p e n d i n g on the t e m p e r a ture, the salt used and the humidity, but all were d e p e n d e n t on i n t e r r a c i a l g r a i n - b o u n d a r y c o n d u c t i o n processes. The p o s s i b l e role of water or h y d r o x i d e cannot be d i s c o u n t e d in work with very h y g r o s c o p i c c o m p o u n d s such as LiI and LiCl. A theoretical sub-project demonstrated the d i f f i c u l t i e s of c o m p u t e r s i m u l a t i o n of o x y g e n - i o n c o n d u c t o r s w h e r e all interatomic p o t e n t i a l s are not very well known. In c o n t r a s t the work on b e t a - a l u m i n a and l i t h i u m n i t r i d e r e v e a l e d the u t i l i t y of m o l e c u l a r d y n a m i c s c a l c u l a t ions w h e r e p o t e n t i a l s and atom p o s i t i o n s are well e s t a b l i s h e d . For Li3N the high ionic c o n d u c t i v i t y was shown to be the result of h i g h l y m o b i l e l i t h i u m vacancies.
Figure
Source
1
Top : C z o c h r a l s k i - g r o w n L i 3 N boule w i t h c y l i n d r i c a l section about 15 mm diameter. B o t t o m : Single c r y s t a l slice 1.5 mm thick. Length al out i 0 mm : Ref. 2 (DTH, Denmark)
The c o n d u c t i v i t y of the o p t i m u m d o p e d c r y s t a l at room t e m p e r a t u r e is very high (6.10-3 ohm -I cm-l) , a factor of two higher than p r e v i o u s l y a c h i e v e d elsewhere. In Figure 2 the effect <)i h y d r o g e n dopant level is shown. The h i g h e s t c o n d u c t i v i t y was o b s e r v e d wilen doping with 0.5 atomic % hydrogen. P o l y c r y s t a l l i n e m a t e r i a l has ~)een mado by m e l t i n g and fast cooling. The samL~les w h i c h have good m e c h a n i c a l pro<~erties have a c o n d u c t i v i t y of 2-3-10 -° ohm -I cm -I at room t e m p e r a t u r e .
J. Jensen / Solid electrolyte battery research within the EEC
11
Z,,5 2"01 LOG r.T LI3N:H.~ AC - coxoucv,v i Tv
40
L,xCOO2
1.0 Celt EMF (voltS)
LixNIO 2
35"
_i
30
)
I
I
I
02
0'4
0'6
0"8
x
25
30
3,5
Figure
3
Source
: Ref.
In
1.0
L,xMO 2
Open-circuit voltages f u n c t i o n of x for the
'
as a cells
LixCoO2/Li, LixNiO2/Li Figure
Source
2
Ionic conductivity of L i 3 N crystals with varying amounts of h y d r o g e n . H y d r o g e n d o p a n t l e v e l i n c r e a s e s in the o r d e r L-25
T h e a p p l i c a t i o n of l i t h i u m n i t r i d e as an electrolyte in r e c h a r g e a b l e batteries w i l l n o w d e p e n d on the a b i l i t y to f a b r i cate thin ceramic material successfully and the d e g r e e to w h i c h the l o w d e c o m p o s i t i o n p o t e n t i a l c a n be k i n e t i c a l l y h i n d e r e d o v e r the l i f e t i m e of a cell. 4.
INSERTION
ELECTRODES
2
(Oxford,
U.,
U.K°)
42
o > 39 J 38 37 36
,
0.5
016
~
,
,
i x ,n L, Co02
07
08
09
~0
i 07
' 08
! 09
' 10
~.~ l.O 3,9
The c o n c e p t of p r e p a r a t i o n of n e w i n s e r t i o n e l e c t r o d e s by e l e c t r o l y t i c e x t r a c t i o n of m o b i l e i o n s f r o m a h o s t m a t r i x at low t e m p e r a t u r e s h a s b e e n studied. Layered metallic oxides AxMO 2 (0
38
' 05
0'6
42 ¸ &.1 •
40' 3.9 38 37 36 05
Figure 4 Source
o6 o7 &8 o9 Cell-voltage versus ion x for L i x C o O 2 / L i current densities : Ref. 2 (Oxford, U.,
i0 compositat v a r i o u s U.K.)
J. Jensen / SolM electro!rte batte
12
The E x x o n c o m p o u n d TiS 2 has b e e n e v a l u a ted u s i n g p o l y e t h y l e n e - o x i d e (PEO)-based c o m p o s i t e as e l e c t r o l y t e m a t e r i a l . The room temperature free-energy/composition c u r v e of L i x T i S 2 s t o i c h i o m e t r i c in s u l p h u r w a s c o n f i r m e d by e x t r a p o l a t i o n from d a t a c o l l e c t e d b e t w e e n 6 0 O c and 120°C ( F i g u r e 5).
i
Slice of I Lithium m e t a l ~ (~O.5mm fhick ~ 6mm diam.)
2.8
=¢~
?
i , i 1~0 pieces of PEO[LiCF3SO3) electrolyte l ~ 50#m thick~ lOmm diam) Folycrystalline pellet of 1"iSz ( ~ 5 m m thick; 6turn diam.)
2"4 Whitfingam, Steele results a tlene29c~o~KOrmfe
2.2
2"0
I I'~ I I.~
t
0 Extrapolated data using PEO electrolyte This work
o
o12
o'.4
o!6
o'.8
~'.o
1!2
X in LixTiS2
Figure Source
5
Open-circuit voltage versus x in L i x T i S 2 : Ref. 2 ( I m p e r i a l C o l l e g e , U.K.)
P r e v i o u s d a t a on L i x T i S 2 h a v e b e e n a s s e s sed and electrochemical studies indic a t e the p r e s e n c e of a c h a r g e - t r a n s f e r r e s i s t a n c e for l i t h i u m e x c h a n g e a c r o s s a liquid electrolyte/TiS 2 interface, p r o b a b l y a r i s i n g f r o m s o l v a t i o n of the l i t h i u m ion in the e l e c t r o l y t e . Transport data measurements using a solid electrolyte t e n d to c o n f i r m the c h a n g e in Li + m o b i l i t y , i n d i c a t i n g t h a t coi n t r o d u c t i o n of s o l v e n t into the TiS 2 lattice from a liquid electrolyte cannot be d i s c o u n t e d . F u r t h e r w o r k is n e e d e d to a c c u m u l a t e d a t a on Li + t r a n s p o r t in T i S ~ , these data being partlcularly important in the p o r o u s c a t h o d e and a l l - s o l i d state cell-modelling w o r k w h i c h has just been started. I n i t i a l w o r k on Cu + c o n d u c t i n g m a t e r i a l s demonstrated that ion-transport across a solid electrolyte/solid electrode interf a c e is a l m o s t s o l e l y c o n t r o l l e d b y m a s s
t r a n s p o r t w i t h the e f f e c t of c h a r g e transfer overpotential processes being negligible. A n u m b e r of i n s e r t i o n c a t h o d e m a t e r i a l s have been investigated and a s e a r c h for insertion anodes with suitable voltages w i t h r e s p e c t to m e t a l l i c l i t h i u m has been started. 5.
APf:LICATION
AND
ASSESSMENT
STUDY
A comprehensive r e v i e w has b e e n m a d e in Sub-Project IV of the role w h i c h a d v a n ced b a t t e r i e s c a n p l a y in E u r o p e earl}, in the 2 1 s t c e n t u r y . The r e s u l t s oC the application s t u d y w e r e p u b l i s h e d as a monograph [3], and a c o n f e r e n c e to d i s c u s s the c o n c l u s i o n s w i t h i n t e r e s t e d p a r t i e s f r o m a~l m e m b e r s t a t e s o f the E u r o p e a n C o m m u n i t y w a s o r g a n i s e d by DG XII in d a n u a r y 1979. It w a s c o n c l u d e d that batteries could play a significant role in d i v e r s i f y i n g the fuel b a s e of t r a n s p o r t by f a c i l i t a t i n g the i n t r o d u c t ion of e l e c t r i c v e h i c l e s , in c o n s e r v i n g energy, particularly in c o m p a r i s o n w i t h synthesizing p e t r o l e u m f r o m coal, in facilitating the o p e r a t i o n s of the e l e c tric u t i l i t i e s , e s p e c i a l l y by local storage of d i s t r i b u t e d e l e c t r i c i t y at: l o a d c e n t r e s , and by p r o v i d i n g a s t o r a g e c o m p o n e n t for s o l a r and w i n d - g e n e r a t e < ! electricity at r e m o t e sites. The d e v e l o p m e n t of a versatile, longlife, l o w - c o s t s e c o n d a r y b a t t e r y is a cornerstone For future progress i n t>oth electric transport and stationary energy storage. An d s s e s s m o n t of systems currently under engineering development ibr traction purposes shows that all of these carry a significant uncertainty of s u c c e s s , b o t h for r e n e w a b l e en©rq'/ s t o r a g e and for t r a c t i o n [>urposes an all-solid-state a l k d l i hera] b a t t e r y £s s e e n as a v e r y a t t r a c t i v e c o n c e p t for future development, it w a s a l s o s h o w n that it is p r i m a r i l y for ~ o v e r n m e n t s to j u d g e the m o s t a p p r o p r i a t e s c a l e ell e l e c t r i c v e h i c l e use and to take up n e c e s s a r y o p t i o n s to hell> i,ring u})out their introduction. Electric vehicles are s e e n as the m a j o r E u r o p e a n m a r k e t for a d v a n c e d , r e c h a r g e a b l e batteries. F u r t h e r a s s e s s m e n t s t u d i e s w e r e rec()mm e n d e d to e x p l o r e the i m p l i c a t i o n s (>f introducing significant n u n b e r s of e l e c t r i c v e h i c l e s in E u r o p e and to h e l p d r a w up a T a r g e t e d C o m m u n i t y Plun for a c t i o n . T h e s e a s s e s s m e n t s t u d i e s sh<)uld be c a r r i e d o u t in p a r a l l e l w i t h c o n t i n u i n g R&D work. 6 The
FLNAL REMARKS ,,~nglo/ban, ish
~rojoct
"Materials
J. Jensen / Solid electrolyte battery research within the EEC
R e s e a r c h for A d v a n c e d B a t t e r i e s " and other E C - r e s e a r c h p r o j e c t s have been c o n c e r n e d with c h a r a c t e r i z a t i o n and dev e l o p m e n t of m a t e r i a l s s u i t a b l e for inc o r p o r a t i o n in a d v a n c e d solid or quasisolid batteries. An E C - c o n t r a c t has r e c e n t l y been signed r e g a r d i n g a new Anglo/Danish project "Advanced Battery D e v e l o p m e n t " . This two-year p r o j e c t (Sept. 1980 - Aug. 1982) will c o n c e n trate m a i n l y on e l e c t r o c h e m i c a l studies and cell design. It is intended to e s t a b l i s h c o n t a c t s with E u r o p e a n industry in order to f a c i l i t a t e the transfer of s c i e n t i f i c r e s u l t s to p r o m o t e engineering d e v e l o p m e n t and future m a n u f a c t ure of a d v a n c e d batteries. ACKNOWLEDGEMENTS The author w i s h e s to a d k n o w l e d g e d i s c u s sions with a number of c o l l e a g u e s w i t h i n the EC E n e r g y C o n s e r v a t i o n R e s e a r c h Programme, in p a r t i c u l a r Prof. J.A.A. Ketelaar, N e t h e r l a n d s and Drs. R.M. Dell and B.C. Tofield, UK. S u p p o r t for this work was o b t a i n e d from E C - c o n t r a c t E E / E 2 / 4 2 9 / 8 0 / D K / H ahd the D a n i s h D e p a r t m e n t of Energy.
REFERENCES
13
:
[i] Tofield, B.C.; Dell, R.M. and Jensen, J. ~ A d v a n c e d B a t t e r i e s , Nature, vol. 276, No. 5685 (1978) 2]7-220 [2] T o f i e l d , B.C. ; R.M., M a t e r i a l s ced B a t t e r i e s , for the Period 31 M a r c h 1980. G 2109 (1981) [3]
Jensen, J. and Dell, R e s e a r c h for A d v a n Final S u m m a r y R e p o r t 1 J a n u a r y 1978 to AERE H a r w e l l Report 1-22
Jensen, J.; M c G e e h i n , P. and Dell, R.M., E l e c t r i c B a t t e r i e s for E n e r g y S t o r a g e and C o n s e r v a t i o n - an applic a t i o n study, O d e n s e U n i v e r s i t y (1979) 1-225