Patent Application: US-44512807-A

Abstract:
this invention concerns a novel method for surface derivatization of electrode materials for li - ion batteries . the derivatization is based on adsorption of a composite assembly consisting of amphiphilic redox active molecule attached to single walled carbon nanotube . its role consists in the enhancement of electronic conductivity of electrode materials , such as phosphate olivines , without requesting any significant increase of the electrode volume and mass . the swcnt is linked to the redox molecule via non - covalent or covalent interaction with the hydrophobic part of the molecule or electrostatic interaction . the hydrophilic part of the molecule serves as the anchoring site for surface modification of the electrode active material . the redox potential of the molecule is close to the redox potential of the electrode active material . the adsorbed assembly of redox - molecule & amp ; swcnt thus improves the charge transfer from a current collector to the electrode active material .

Description:
a redox active centre may be an organic compound or a metal complex having suitable redox potential as that of the lithium insertion material . in a preferred configuration the redox active centre is of the type given below , wherein π represents schematically the π system of the aforesaid substituent , ral represents an aliphatic substituent with a saturated chain portion bound to the π system , and wherein q represents an integer , indicating that π may bear more than one substituent ral . the π system π may be an unsaturated chain of conjugated double or triple bonds of the type wherein rar is a h or monocyclic or oligocyclic aryl from c6 to c22 , wherein r1 , r ′ 1 are same or different from — ch 2 po 3 h 2 , — ch 2 co 2 h , — ch 2 so 3 h , — ch 2 conhoh , — ch 2 po 4 h 2 , — ch 2 so 4 h 2 , x ≧ 0 , and 0 & lt ; n & lt ; 20 . according to a preferred embodiment , d is selected from benzol , naphtaline , indene , substituted triarylamine , fluorene , phenantrene , anthracene , triphenylene , pyrene , pentalene , perylene , indene , azulene , heptalene , biphenylene , indacene , phenalene , acenaphtene , fluoranthene , and heterocyclic compounds pyridine , pyrimidine , pyridazine , quinolizidine , quinoline , isoquinoline , quinoxaline , phtalazine , naphthyridine , quinazoline , cinnoline , pteridine , indolizine , indole , isoindole , carbazole , carboline , acridine , phenanthridine , 1 , 10 - phenanthroline , thiophene , thianthrene , oxanthrene , and derivatives thereof , optionally be substituted . according to a preferred embodiment , d is selected from structures of formula ( 1 - 11 ) given below : in which each of z 1 , z 2 and z 3 is the same or different and is selected from the group consisting of o , s , so , so 2 , nr 1 , n + ( r 1 ′ )( 1 ″ ), c ( r 2 )( r 3 ), si ( r 2 ′ )( r 3 ′ ) and p ( o )( or 4 ), wherein r 1 , r 1 ′ and r 1 ″ are the same or different and each is selected from the group consisting of hydrogen atoms , alkyl groups , haloalkyl groups , alkoxy groups , alkoxyalkyl groups , aryl groups , aryloxy groups , and aralkyl groups , which are substituted with at least one group of formula — n + ( r 5 ) 3 wherein each group r 5 is the same or different and is selected from the group consisting of hydrogen atoms , alkyl groups and aryl groups , r 2 , r 3 , r 2 ′ and r 3 ′ are the same or different and each is selected from the group consisting of hydrogen atoms , alkyl groups , haloalkyl groups , alkoxy groups , halogen atoms , nitro groups , cyano groups , alkoxyalkyl groups , aryl groups , aryloxy groups and aralkyl groups or r 2 and r 3 together with the carbon atom to which they are attached represent a carbonyl group , and r 4 is selected from the group consisting of hydrogen atoms , alkyl groups , haloalkyl groups , alkoxyalkyl groups , aryl groups , aryloxy groups and aralkyl groups . x = po 3 h 2 or co 2 h or so 3 h or conhoh or po 4 h 2 a = f or cl or br i or no 2 or coor or alkyl ( c 1 to c 20 ) or cf 3 or cor or och 3 or h b = f or cl or br i or no 2 or coor or alkyl ( c 1 to c 20 ) or cf 3 or cor or och 3 x = po 3 h 2 or co 2 h or so 3 h or conhoh or po 4 h 2 x = po 3 h 2 or co 2 h or so 3 h or conhoh or po 4 h 2 f or cl or br i or no 2 or coor or alkyl ( c 1 to c 20 ) or cf 3 or cor or och 3 or h wherein a and b are same or different from h , or , cl , br , f , i , no2 , cf3 , cocf3 , r is h or ( ch 2 ) p - e n -( ch 2 ) m - acc ( p = 0 to 24 , linear or branched or with cycles ; n = 0 to 24 , m = 0 to 24 , linear or branched or with cycles ; e is — ch ═ ch —, or — c ≡ c —, or — och 2 ch 2 —, and acc is po 3 h 2 or co 2 h or so 3 h or conhoh or po 4 h 2 or so 4 h 2 wherein x and y are same or different from h , or , cl , br , f , i , no2 , cf3 , cocf3 , r is h or ( ch 2 ) p - e n -( ch 2 ) m - acc ( p = 0 to 24 , linear or branched or with cycles ; n = 0 to 24 , m = 0 to 24 , linear or branched or with cycles ; e is — ch ═ ch —, or — c ≡ c —, or — och 2 ch 2 —, and acc is po 3 h 2 or co 2 h or so 3 h or conhoh or po 4 h 2 or so 4 h 2 wherein a , b and c are same or different from h , or , cl , br , f , i , no2 , cf3 , cocf3 , linear or branched alkyl group from 1 to 20 carbon atoms , r is h or ( ch 2 ) p - e n -( ch 2 ) m - acc ( p = 0 to 24 , linear or branched or with cycles ; n = 0 to 24 , m = 0 to 24 , linear or branched or with cycles ; e is — ch ═ ch —, or — c ≡ c —, or — och 2 ch 2 —, and acc is po 3 h 2 or co 2 h or so 3 h or conhoh or po 4 h 2 or so 4 h 2 alternatively a redox active centre may be a metal complex having suitable redox potential as that of the lithium insertion material . in metal complexes as redox active centers , the preferred ligands coordinated to the metal , according to the invention are metal complexes having a formula selected from x = po 3 h 2 or co 2 h or so 3 h or conhoh or po 4 h 2 or so 4 h 2 p = f or cl or br or i or no 2 or cn or ncse or ncs or nco wherein b = alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 is same or different from coors or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or a linear or branched alkyl ( c 1 to c 20 ) or h ( where r 3 is an alkyl ( c 1 to c 20 ) or h ) or comprises an additional π system located in conjugated relationship with the primary π system , the said substituent is of the type wherein π represents schematically the π system of the aforesaid substituent , ral represents an aliphatic substituent with a saturated chain portion bound to the π system , and wherein q represents an integer , indicating that π may bear more than one substituent ral . wherein at least one of substituents — r , — r 1 , — r 2 is of formula ( 1 ), ( 2 ) or ( 3 ) wherein rar is a h or monocyclic or oligocyclic aryl from c6 to c22 , wherein - ral is a h or — r1 or — o — r1 or — n ( r1 ) 2 or — nhr1 or wherein r1 , r ′ 1 are same or different from — ch 2 po 3 h 2 , — ch 2 co 2 h , — ch 2 so 3 h , — ch 2 conhoh , — ch 2 po 4 h 2 , — ch 2 so 4 h 2 , x ≧ 0 , and 0 & lt ; n & lt ; 20 . wherein the other one ( s ) of substituent ( s ) — r , — r 1 , — r 2 is ( are ) the same or a different substituent of formula ( 1 ), ( 2 ) or ( 3 ), or is ( are ) selected from — h , — oh , — r 3 , — or 3 , cooh , cocf3 , cn , br , cl , f , i , cf3 , or — n ( r 3 ) 2 , wherein r 3 is a linear or branched alkyl of 1 to 20 carbon atoms . x = f or cl or br or i or no 2 or cn or ncse or ncs or nco wherein b = linear or branched alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 is same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or a linear or branched alkyl ( c 1 to c 20 ) or h ( where r 3 is an alkyl ( c 1 to c 20 ) or h ) or comprises an additional π system located in conjugated relationship with the primary π system , the said substituent is of the type wherein π represents schematically the π system of the aforesaid substituent , ral represents an aliphatic substituent with a saturated chain portion bound to the π system , and wherein q represents an integer , indicating that π may bear more than one substituent ral . wherein at least one of substituents — r , — r 1 , — r 2 is of formula ( 1 ), ( 2 ) or ( 3 ) wherein rar is a h or monocyclic or oligocyclic aryl from c6 to c22 , wherein - ral is a h or — r1 or — o — r1 or — n ( r1 ) 2 or — nhr1 or wherein r1 , r ′ 1 are same or different from — ch 2 po 3 h 2 , — ch 2 co 2 h , — ch 2 so 3 h , — ch 2 conhoh , — ch 2 po 4 h 2 , — ch 2 so 4 h 2 , x ≧ 0 , and 0 & lt ; n & lt ; 20 . wherein the other one ( s ) of substituent ( s ) — r , — r 1 , — r 2 is ( are ) the same or a different substituent of formula ( 1 ), ( 2 ) or ( 3 ), or is ( are ) selected from — h , — oh , — r 3 , — or 3 , cooh , cocf 3 , cn , br , cl , f , i , cf3 , or — n ( r 3 ) 2 , wherein r 3 is a linear or branched alkyl of 1 to 20 carbon atoms . wherein b = alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 may be same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or alkyl ( c 1 to c 20 ) or h where r 3 is an alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 is same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or a linear or branched alkyl ( c 1 to c 20 ) or h ( where r 3 is a linear or branched alkyl ( c 1 to c 20 ) or h ) or comprises an additional π system located in conjugated relationship with the primary π system , the said substituent is of the type wherein π represents schematically the π system of the aforesaid substituent , ral represents an aliphatic substituent with a saturated chain portion bound to the π system , and wherein q represents an integer , indicating that π may bear more than one substituent ral . wherein at least one of substituents — r , — r 1 , — r 2 is of formula ( 1 ), ( 2 ) or ( 3 ) wherein rar is a h or monocyclic or oligocyclic aryl from c6 to c22 , wherein - ral is a h or — r1 or — o — r1 or — n ( r1 ) 2 or — nhr1 or wherein r1 , r ′ 1 are same or different from — ch 2 po 3 h 2 , — ch 2 co 2 h , — ch 2 so 3 h , — ch 2 conhoh , — ch 2 po 4 h 2 , — ch 2 so 4 h 2 , x ≧ 0 , and 0 & lt ; n & lt ; 20 . wherein the other one ( s ) of substituent ( s ) — r , — r 1 , — r 2 is ( are ) the same or a different substituent of formula ( 1 ), ( 2 ) or ( 3 ), or is ( are ) selected from — h , — oh , — r 3 , — or 3 , cooh , cocf3 , cn , br , cl , f , i , cf3 , or — n ( r 3 ) 2 , wherein r 3 is a linear or branched alkyl of 1 to 20 carbon atoms . r , r 1 , r 2 may be same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or alkyl ( c 1 to c 20 ) or h where r 3 is an alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 is same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or a linear or branched alkyl ( c 1 to c 20 ) or h ( where r 3 is a linear or branched alkyl ( c 1 to c 20 ) or h ) or comprises an additional π system located in conjugated relationship with the primary π system , the said substituent is of the type wherein π represents schematically the π system of the aforesaid substituent , ral represents an aliphatic substituent with a saturated chain portion bound to the π system , and wherein q represents an integer , indicating that π may bear more than one substituent ral . wherein at least one of substituents — r , — r 1 , — r 2 is of formula ( 1 ), ( 2 ) or ( 3 ) wherein rar is a h or monocyclic or oligocyclic aryl from c6 to c22 , wherein - ral is a h or — r1 or — o — r1 or — n ( r1 ) 2 or — nhr1 or wherein r1 , r ′ 1 are same or different from — ch 2 po 3 h 2 , — ch 2 co 2 h , — ch 2 so 3 h , — ch 2 conhoh , — ch 2 po 4 h 2 , — ch 2 so 4 h 2 , x ≧ 0 , and 0 & lt ; n & lt ; 20 . wherein the other one ( s ) of substituent ( s ) — r , — r 1 , — r 2 is ( are ) the same or a different substituent of formula ( 1 ), ( 2 ) or ( 3 ), or is ( are ) selected from — h , — oh , — r 3 , — or 3 , cooh , cocf 3 , cn , br , cl , f , i , cf3 , or — n ( r 3 ) 2 , wherein r 3 is a linear or branched alkyl of 1 to 20 carbon atoms . x = po 3 h 2 or co 2 h or so 3 h or conhoh or po 4 h 2 or so 4 h 2 p = f or cl or br or i or no 2 or cn or ncse or ncs or nco wherein b = alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 may be same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or alkyl ( c 1 to c 20 ) or h where r 3 is an alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 is same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or a linear or branched alkyl ( c 1 to c 20 ) or h ( where r 3 is a linear or branched alkyl ( c 1 to c 20 ) or h ) or comprises an additional π system located in conjugated relationship with the primary π system , the said substituent is of the type wherein π represents schematically the π system of the aforesaid substituent , ral represents an aliphatic substituent with a saturated chain portion bound to the π system , and wherein q represents an integer , indicating that π may bear more than one substituent ral . wherein at least one of substituents — r , — r 1 , — r 2 is of formula ( 1 ), ( 2 ) or ( 3 ) wherein rar is a h or monocyclic or oligocyclic aryl from c6 to c22 , wherein - ral is a h or — r1 or — o — r1 or — n ( r1 ) 2 or — nhr1 or wherein r1 , r ′ 1 are same or different from — ch 2 po 3 h 2 , — ch 2 co 2 h , — ch 2 so 3 h , — ch 2 conhoh , — ch 2 po 4 h 2 , — ch 2 so 4 h 2 , x ≧ 0 , and 0 & lt ; n & lt ; 20 . wherein the other one ( s ) of substituent ( s ) — r , — r 1 , — r 2 is ( are ) the same or a different substituent of formula ( 1 ), ( 2 ) or ( 3 ), or is ( are ) selected from — h , — oh , — r 3 , — or 3 , cooh , cocf 3 , cn , br , cl , f , i , cf 3 , or — n ( r 3 ) 2 , wherein r 3 is a linear or branched alkyl of 1 to 20 carbon atoms . x = po 3 h 2 or co 2 h or so 3 h or conhoh or po 4 h 2 or so 4 h 2 wherein b = alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 may be same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or alkyl ( c 1 to c 20 ) or h where r 3 is an alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 is same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or a linear or branched alkyl ( c 1 to c 20 ) or h ( where r 3 is a linear or branched alkyl ( c 1 to c 20 ) or h ) or comprises an additional π system located in conjugated relationship with the primary π system , the said substituent is of the type wherein π represents schematically the π system of the aforesaid substituent , ral represents an aliphatic substituent with a saturated chain portion bound to the π system , and wherein q represents an integer , indicating that π may bear more than one substituent ral . wherein at least one of substituents — r , — r 1 , — r 2 is of formula ( 1 ), ( 2 ) or ( 3 ) wherein rar is a h or monocyclic or oligocyclic aryl from c6 to c22 , wherein - ral is h or — r1 or — o — r1 or — n ( r1 ) 2 or — nhr1 or wherein r1 , r ′ 1 are same or different from — ch 2 po 3 h 2 , — ch 2 co 2 h , — ch 2 so 3 h , — ch 2 conhoh , — ch 2 po 4 h 2 , — ch 2 so 4 h 2 , x ≧ 0 , and 0 & lt ; n & lt ; 20 . wherein the other one ( s ) of substituent ( s ) — r , — r 1 , — r 2 is ( are ) the same or a different substituent of formula ( 1 ), ( 2 ) or ( 3 ), or is ( are ) selected from — h , — oh , — r 3 , — or 3 , cooh , cocf 3 , cn , br , cl , f , i , cf 3 , or — n ( r 3 ) 2 , wherein r 3 is a linear or branched alkyl of 1 to 20 carbon atoms . x = po 3 h 2 or co 2 h or so 3 h or conhoh or po 4 h 2 or so 4 h 2 wherein b = alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 may be same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or alkyl ( c 1 to c 20 ) or h where r 3 is an alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 is same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or a linear or branched alkyl ( c 1 to c 20 ) or h ( where r 3 is a linear or branched alkyl ( c 1 to c 20 ) or h ) or comprises an additional π system located in conjugated relationship with the primary π system , the said substituent is of the type wherein π represents schematically the π system of the aforesaid substituent , ral represents an aliphatic substituent with a saturated chain portion bound to the π system , and wherein q represents an integer , indicating that π may bear more than one substituent ral . wherein at least one of substituents — r , — r 1 , — r 2 is of formula ( 1 ), ( 2 ) or ( 3 ) wherein rar is a h or monocyclic or oligocyclic aryl from c6 to c22 , wherein - ral is a h — r1 or — o — r1 or — n ( r1 ) 2 or — nhr1 or wherein r1 , r ′ 1 are same or different from — ch 2 po 3 h 2 , — ch 2 co 2 h , — ch 2 so 3 h , — ch 2 conhoh , — ch 2 po 4 h 2 , — ch 2 so 4 h 2 , x ≧ 0 , and 0 & lt ; n & lt ; 20 . wherein the other one ( s ) of substituent ( s ) — r , — r 1 , — r 2 is ( are ) the same or a different substituent of formula ( 1 ), ( 2 ) or ( 3 ), or is ( are ) selected from — h , — oh , — r 3 , — or 3 , cooh , cocf3 , cn , br , cl , f , i , cf3 , or — n ( r 3 ) 2 , wherein r 3 is a linear or branched alkyl of 1 to 20 carbon atoms . wherein b = alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 may be same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or alkyl ( c 1 to c 20 ) or h where r 3 is an alkyl ( c 1 to c 20 ) or h r , r 1 , r 2 is same or different from coor 3 or po 3 r 3 or so 3 r 3 or conr 3 or 3 or so 4 r 3 or cor 3 or cf 3 or cocf 3 or or 3 or no 2 or f or cl or br or i or nr 3 or a linear or branched alkyl ( c 1 to c 20 ) or h ( where r 3 is a linear or branched alkyl ( c 1 to c 20 ) or h ) or comprises an additional π system located in conjugated relationship with the primary π system , the said substituent is of the type wherein π represents schematically the π system of the aforesaid substituent , ral represents an aliphatic substituent with a saturated chain portion bound to the π system , and wherein q represents an integer , indicating that π may bear more than one substituent ral . wherein at least one of substituents — r , — r 1 , — r 2 is of formula ( 1 ), ( 2 ) or ( 3 ) wherein rar is a h or monocyclic or oligocyclic aryl from c6 to c22 , wherein r1 , r ′ 1 are same or different from — ch 2 po 3 h 2 , — ch 2 co 2 h , — ch 2 so 3 h , — ch 2 conhoh , — ch 2 po 4 h 2 , — ch 2 so 4 h 2 , x ≧ 0 , and 0 & lt ; n & lt ; 10 . wherein the other one ( s ) of substituent ( s ) — r , — r 1 , — r 2 is ( are ) the same or a different substituent of formula ( 1 ), ( 2 ) or ( 3 ), or is ( are ) selected from — h , — oh , — r 3 , — or 3 , cooh , cocf3 , cn , br , cl , f , i , cf3 , or — n ( r 3 ) 2 , wherein r 3 is a linear or branched alkyl of 1 to 20 carbon atoms . lifepo 4 was synthesized by a variant of solid state reaction [ 15 ] employing fec 2 o 4 . 2h 2 o and lih 2 po 4 as precursors . their stoichiometric amounts were mixed and ground in a planetary ball - milling machine for 4 h . then the powder was calcined in a tube furnace with flowing ar — h 2 ( 92 : 8 v / v ) at 600 ° c . for 24 h . after cooling down to room temperature , the sample was ground in agate mortar . the bet surface area of the powder was ca . 5 m 2 / g with an average particle size of 400 nm . x - ray diffraction confirmed the phase purity . the ru - bipyridine complex , naru ( 4 - carboxylic acid - 4 ′- carboxylate ( 4 , 4 ′- dionyl - 2 , 2 ′ bipyridine )( ncs ) 2 , coded as z - 907na was synthesized as described elsewhere [ 16 ] . single walled carbon nanotubes were grown by catalytic laser ablation method . the average diameter of tubes was determined by raman and vis - nir spectroscopy to be ca . 1 . 3 - 1 . 4 nm . other chemicals were from commercial sources and were used as received . swcnt were dispersed with solutions of surfactants ( either pyrene butanoic acid in dimethylformamide ( dmf ) or z - 907na in acetonitrile + tert - butanol ( 1 : 1 ) ( an / t - buoh ) by sonication . the optimized synthetic protocol for z - 907na was as follows : 9 mg of swcnt was sonicated for 2 hours with 10 ml of 6 · 10 − 4 m z - 907na in acetonitrile + t - butanol ( 1 : 1 ). the resulting black - brown solution was centrifuged at 5000 rpm for 1 hour , while ca . 4 mg of undissolved carbon remained as a sediment . this working solution ( abbreviated further as z - 907na / swcnt ) was stable for at least weeks at room temperature without precipitation . hence , the solution contained ca . 5 mg of dispersed swcnt ( 417 μmol ) and 6 μmol of z - 907na ( molar ratio c / z - 907na ≈ 70 ). the olivine lifepo 4 ( 200 mg ) was mixed with several portions ( 0 . 5 - 0 . 7 ml ) of this working solution . at the initial stages , the supernatant turned to colorless within several seconds after mixing . after each addition of the z - 907na / swcnt solution , the slurry was centrifuged , supernatant separated and a next portion of the solution was added . this procedure was repeated until the supernatant did not decolorize . the total amount of applied solution was 1 . 5 ml . finally the powder was washed with an / t - buoh and dried at room temperature . the same synthetic protocol was also adopted also for surface derivatization of lifepo 4 with pyrenebutanoic acid / swcnt . electrodes were prepared by mixing the powder of surface derivatized lifepo 4 with 5 wt % of polyvinylidene fluoride ( pvdf ) dissolved in n - methyl - 2 - pyrolidone . the resulting homogeneous slurry was then doctor - bladed onto f - doped conducting glass ( fto ) and dried at 100 ° c . overnight . alternatively the slurry was coated on alumina current collector and dried at 100 ° c . overnight . the typical film mass was 1 . 5 - 2 mg / cm 2 . blank electrodes from pure lifepo 4 were prepared in the same way for reference experiments . a second reference material was a carbon - coated lifepo 4 ( nanomyte be - 20 from nei corporation , usa ). the electrode was assembled in the electrochemical cell with li reference and counter electrodes or alternatively in the swagelok cell with li negative electrode . vis - nir spectra were measured at varian cary 5 spectrometer in 2 mm glass optical cells . the measurement was carried out in transmission mode with integrating sphere . electrochemical experiments employed an autolab pgstat 30 potentiostat . the electrolyte was 1 m lipf 6 in ethylene carbonate ( ec )/ dimethyl carbonate ( dmc ) ( 1 : 1 , v : v ). the reference and counter electrodes were from li - metal . fig1 shows the vis - nir spectra of 6 × 10 − 4 m solution of z - 907na complex and the working solution z - 907na / swcnt . in the latter case , we detected the characteristic features of carbon nanotubes . semiconducting swcnt are characterized by optical transitions between van hove singularities at ca . 0 . 7 ev and 1 . 3 ev for the first and second pair of singularities , respectively . metallic tubes manifest themselves by a transition at 1 . 8 - 1 . 9 ev , which corresponds to the first pair of van hove singularities . the main peak of z - 907na occurs at ca . 2 . 35 ev , and it is blue shifted by ca . 50 mev in the swcnt - containing solution ( fig1 ). obviously , the z - 907na complex acts as an efficient surfactant for swcnt , due to the presence of hydrophobic aliphatic c9 chains ( scheme 1 ), which interact with the carbon tube surface . there are many other molecules reported for solubilization of swcnt , the most popular being sodium dodecyl sulfate [ 17 ] , but , to the best of our knowledge , the solubilization of swcnt by ru - bipyridine complexes is here demonstrated for the first time . fig2 ( left chart ) shows the cyclic voltammogram of a pure ( carbon free ) lifepo 4 ( bonded with 5 % pvdf ), which was treated by dip - coating into 6 × 10 − 4 mol / l solution of z - 907na for 3 hours , rinsed with an / t - buoh and dried in vacuum at room temperature . the right chart plots analogous data for pure lifepo 4 electrode , which was treated with z - 907na / swcnt solution in the same way . we see a plateau anodic current , which indicates the so - called “ molecular wiring ” of lifepo 4 [ 18 ] . the z - 907na complex ( as in scheme 1 , can transport electronic charge via surface percolation in adsorbed monolayer even on insulating surfaces like al 2 o 3 [ 19 ] . here , the ncs groups act as mediators for the surface - confined hole percolation , and the bipyridine ligands transport electrons . the hole diffusion coefficient within adsorbed z - 907na was of the order of 10 − 9 cm 2 / s above the charge percolation threshold , ca . 50 % of surface coverage [ 19 ] . the effect of molecular wiring was recently applied to the lifepo 4 electrode material , which can be wired by 4 -( bis ( 4 - methoxyphenyl ) amino ) benzylphosphonic acid [ 20 ] . in this case , the cross - surface hole percolation was followed by interfacial charging and discharging of lifepo 4 with li + ions [ 20 ] . our data confirm that the hole - transport wiring is possible also with the z - 907na complex , while a similar anodic current ( exceeding 0 . 2 ma / cm 2 ) can be wired to the lifepo 4 electrode at 0 . 1 v / s . the formal redox potential of z - 907na adsorbed on inert tio 2 surface was about 3 . 5 v vs . li / li +[ 19 , 21 ] , which is just sufficient for the anodic wiring of lifepo 4 ( redox potential 3 . 45 v vs . li / li + ) but not for cathodic wiring [ 20 ] . our data on fig2 also confirm that the cooh / coona are suitable anchoring groups for lifepo 4 , similar to the phosphonic acid anchoring group employed previously [ 20 ] . the total anodic charge was between 2 to 4 mc ( 0 . 4 to 0 . 7 mah / g ) for the electrode in fig2 ( left chart ) at the given scan rates . this charge was not much larger at slower scanning and moreover , the electrode was unstable during repeated cycling at slower scan rates . the molecular wiring via adsorbed z - 907na is sensitive to imperfections in the surface layer , which hamper the hole percolation . fig2 ( right chart ) shows a variant of the previous experiment , where the lifepo 4 film was treated by dip - coating into z - 907na / swcnt solution . surprisingly , the anodic current is now considerably smaller , which may be due to poor accessibility of the pores in the pre - deposited lifepo 4 layer for swcnt . as the carbon tubes are typically 1 - 10 μm long , they cannot easily interpenetrate the compact porous solid . hence , the z - 907na / swcnt assemblies reside prevailingly on top of the lifepo 4 layer . we may assume that either some free complex ( z - 907na ) may still be present in our working solution z - 907na / swcnt or may be partly released from the swcnt upon interaction with the lifepo 4 surface . this causes poor surface coverage and attenuated molecular wiring in this case . however , this situation changes dramatically , if the surface derivatization is carried out with the starting lifepo 4 powder instead of the doctor - bladed porous film . fig3 ( left chart ) shows cyclic voltammogram of this electrode compared to the voltammograms of an electrode , which was fabricated in the same way , but instead of using z - 907na complex as a surfactant , the swcnt were solubilized by pyrene butanoic acid . obviously , this electrode shows practically no activity , indicating that the sole carbon nanotubes do not promote the charging / discharging of lifepo 4 . also the electrode from carbon - coated lifepo 4 ( nanomyte be - 20 , nei ) shows much smaller activity compared to our z - 907na / swcnt electrode at the same conditions . a comparative experiment with z - 907na / swcnt treated limnpo 4 powder also showed practically no electrochemical activity ( data not shown ). the charging / discharging of lifepo 4 via the surface attached z - 907na / swcnt assemblies was reasonably reversible , providing at 0 . 1 mv / s scan rate the specific capacity of ca . 41 mah / h for anodic process and 40 mah / g for cathodic process ( see data on fig3 ). the electrode was also quite stable , showing no obvious capacity fading in repeated voltammetric scans . the exceptional properties of our z - 907na / swcnt electrode are further demonstrated by galvanostatic charging / discharging cycle . fig3 ( right chart ) demonstrates that the z - 907na / swcnt electrode delivered at the charge rate c / 5 and cut - off potentials 4 and 2 . 7 v vs . li / li + the anodic charge of 390 mc ( 51 mah / g ) and the cathodic charge of 337 mc ( 44 mah / g ). a comparative test with carbon - coated lifepo 4 ( nanomyte be - 20 , nei ) cannot be carried out due to negligible activity of this electrode at the c / 5 rate . even at ten times slower charging , this carbon - coated electrode exhibits much worse performance ( curve b in fig3 , right chart ). the applied amount of working solution z - 907na / swcnt ( 1 . 5 ml ; 6 × 10 − 4 mol / l z - 907na ) gives the upper limit of the adsorbed z - 907na to be 0 . 9 μmol and the amount of adsorbed carbon ( in the form of swcnt ) to be 6 . 3 μmol per 200 mg of lifepo 4 ( see experimental section ). the concentration of elemental carbon from swcnt was , therefore , less than 0 . 04 wt % in the final solid material ). from the bet surface area of lifepo 4 we can calculate that the surface coverage of z - 907na is equivalent to about one molecule per 2 nm 2 . this is not far from the monolayer coverage , if we take into account the usual dimensions of ru - bipyridine molecules [ 22 ] . the unprecedented activity of the electrode composite of lifepo 4 / z - 907na / swcnt is obviously due to the presence of carbon nanotubes , which can quickly transport the charge mediated by z - 907na complex towards the olivine surface . this beneficial role of carbon nanotubes even promotes the cathodic process . this is almost absent in sole molecular wiring , due to low driving force of the redox process in z - 907na for the reduction of li 1 - x fepo 4 back to the starting stoichiometric composition ( fig2 ). reagent f . w ( uma ) g ml mol i 540 . 76 0 . 5 0 . 925 · 10 − 3 hcl 37 % 35 . 5 5 method : in a 25 ml three necked round bottomed flask ( equipped with a condenser ) were placed 0 . 5 g of i dissolved in a 12n hcl water solution ( 5 ml ). the solution was stirred at reflux temperature for about one night . the reactor was kept in the dark . the reaction was followed by 1h - nmr until the signal of ch 2 of the esters has disappeared . then the excess of chlorhydric acid was distilled off at reduced pressure , and the product collected as brown viscous oil . the product was dissolved two to three times in toluene and the solvent distilled off at reduced pressure . no other purification was needed . yield : quatitative . 1 h - nmr ( cdcl 3 ): 1 . 18 - 1 . 35 ppm ( bm , 36h , h chain + c ( ch 3 ) 3 ); 1 . 48 ppm ( m , 2h , h chain ); 1 . 81 ppm ( m , 4h , h chain ); 3 . 80 ppm ( s , 3h , o ch 3 ); 3 . 94 ppm ( t , 2h , o ch 2 ch 2 ); 6 . 81 ppm ( d , 2h , h ar ). reagent f . w ( uma ) g mol i 236 . 35 1 4 . 23 · 10 − 3 ii 328 3 . 5 1 . 06 · 10 − 2 nah 24 0 . 11 4 . 6 · 10 − 3 method : in a 100 ml three necked round bottomed flask ( equipped with a schlenk cock ) were placed 0 . 11 g of nah in anhydrous thf ( 15 ml ) and 1 gram ( 4 . 23 mmol ) of i . a gas evolution occurred for a few minutes , when it was finished 3 . 5 g ( 10 mmol ) of 1 , 12 - dibromododecane ( dissolved in 15 ml of thf ) were added . the mixture was stirred at room temperature for about one hour , then the system was refluxed for 20 hours . the reactor was kept in the dark and in a inert atmosphere ( argon ). then the mixture was cooled to room temperature and 60 ml of water were added . the organic phase was extracted with dcm ( 3 × 60 ml ), dried with cacl 2 and the solvent removed under vacuum to give a slightly yellow viscous liquid . the product was purified by flash chromatography on silica gel ( ethyl acetate / petroleum ether 5 : 95 ), giving 1 . 7 g of pure ( gc / ms ) product ( colourless liquid ). yield : 83 %. ms ( ei ): 482 ( m +), 484 ( m + 2 ), 236 ; 221 ( 100 %). 1 h - nmr ( cdcl 3 , t . a . ): 1 . 28 - 1 . 32 ppm ( bm , 36h , h chain + c ( ch 3 ) 3 ); 1 . 81 ppm ( bm , 4h , h chain ); 3 . 76 ppm ( s , 3h , o ch 3 ); 3 . 90 ppm ( t , 2h , o ch 2 ch 2 ); 4 . 10 ppm ( t , 2h , ch 2 br ); 6 . 81 ppm ( bs , 2h , h ar ). reagent f . w ( uma ) g ml mol i 483 . 56 1 2 . 07 · 10 − 3 ii 166 . 16 8 method : in a 25 ml three necked round bottomed flask ( equipped with a condenser ) were placed 1 g of i dissolved in triethylphosphite ( 8 ml ). the solution was stirred at 120 ° c . for about three hour . the reactor was kept in the dark and in a inert atmosphere ( argon ). then the excess of triethylphosphite was distilled off at reduced pressure and the product collected as brown liquid . the purification was carried out by flash chromatography on silica gel ( petrol ether / ethyl acetate 5 : 1 ). the pure product is a colourless liquid ( yield : 85 %). ms ( ei ): 540 ( m +); 305 ( 100 %). 1 h - nmr ( cdcl 3 ): 1 . 18 - 1 . 35 ppm ( bm , 42h , h chain + poch 2 ch 3 + c ( ch 3 ) 3 ); 1 . 71 ppm ( m , 2h , h chain ); 1 . 81 ppm ( m , 4h , h chain ); 3 . 80 ppm ( s , 3h , o ch 3 ); 3 . 94 ppm ( t , 2h , o ch 2 ch 2 ); 4 . 09 ppm ( m , 4h , po ch 2 ch 3 ); 6 . 81 ppm ( d , 2h , h ar ). fig4 shows the cyclic voltammogram of dw adsorbed on mesoscopic tio 2 electrode . dw exhibits reversible charge - transfer reaction , despite the tio 2 is insulating in this potential region and inactive for ( dark ) electrochemistry . this is an evidence for cross - surface electron / hole percolation in the dw molecules . uv - spectrophotometry indicated the surface coverage of tio 2 with dw ref 23 to be 0 . 3 nmol / cm 2 , which translates into ≈ 2 molecules / nm 2 . ( the surface coverage is refereed to the overall physical surface of the electrode material , which was 55 cm 2 ). the integrated voltammetric charge at the slowest scan ( 1 mv / s ) was 1 . 51 mc , which translates into 0 . 28 nmol / cm 2 . hence , the dw makes roughly a monolayer on the tio 2 surface , and is fully active for ambipolar charge transport from the fto support . inset in fig4 shows that the forward peak current density , j p scales with the square root of the scan rate , v 1 / 2 according to the randles - sevcik equation : j p = 2 . 69 · 10 5 n 3 / 2 d + 1 / 2 c 0 v 1 / 2 ( 1 ) ( n is number of electrons ). the concentration of dw in the film ( thickness 2 . 5 μm ) equals c 0 = 3 . 3 · 10 − 4 mol / cm 3 . from the slope of the line in fig4 ( inset ) and eq . ( 1 ) we can calculate the diffusion coefficient d + = 9 · 10 − 10 cm 2 / s . this coefficient describes actually the cross surface motion of holes though the dw monolayer , and not the mass transport , because the translational motion of adsorbed molecules is obviously excluded . therefore , the charge transfer stops , if a percolation threshold is achieved . the found d + is not too far from the value for ru - bipyridine complex z - 907 adsorbed on tio 2 [ d + =( 1 . 5 to 4 . 1 )· 10 − 9 cm 2 / s ], but is by three orders of magnitude smaller than the value of “ real ” diffusion coefficient of dbb dissolved in electrolyte solution ( 1 . 6 · 10 − 6 cm 2 / s ). fig5 shows cyclic voltammograms of dw on tio 2 . the peak - to - peak splitting for the first scan was between 41 to 59 mv . the splitting is narrower than 60 / n mv expected for a reversible redox system in solution , which indicates the surface confinement of dw . during repeated scanning , the integral voltammetric charge drops by ca . 2 % per cycle and also the peak - to - peak splitting increases . this illustrates that there are certain limits of the stability of the dw / tio 2 system at these conditions . fig6 shows the cyclic voltammograms of dw adsorbed on limnpo 4 electrode . the behavior is similar to that on tio 2 ( cf . fig4 ). in other words , limnpo 4 behaves like an inert ( insulating ) support , and molecular wiring towards oxidative delithiation of limnpo 4 is absent . this is understandable because the available redox potential of dw does not provide enough driving force for this reaction . by using the same evaluation routine as for tio 2 we can calculate the diffusion coefficient from the slope of j p vs . v 1 / 2 ( inset in fig3 ) to be : d + = 3 · 10 − 9 cm 2 / s ref23 . interestingly , the cross - surface charge transport is ca . three times faster on limnpo 4 compared to tio 2 . this might be due to different surface morphology : whereas tio 2 is a mesoporous material with statistically sintered 20 - nm particles , the limnpo 4 consists of platelets ca . 200 nm in size , exposing the ( 010 ) faces on which the dw molecules can be assembled in a more organized way . although limnpo 4 is intact for molecular wiring ( cf . fig6 ), this effect is well expressed for lifepo 4 olivine . fig7 a shows that a constant current flows at potentials above ca . 4 . 1 v . this plateau (“ wiring current ”) is indicative for subsequent chemical reaction of the oxidized molecule ( dw + ) with lifepo 4 olivine causing its oxidative delithiation : interestingly , at faster scanning ( 200 mv / s ) we may trace also the parent peaks of the dw redox couple , indicating that a fast molecular charge transfer reaction foreruns the interfacial hole injection into lifepo 4 . this kind of behaviour was not yet reported for molecular wiring or targeting of lifepo 4 . at slower scanning ( 20 mv / s , the molecular couple is not seen , and the voltammogram is dominated by the wiring current only . both curves in fig7 a were acquired on fresh ( non - treated ) electrodes with roughly identical film &# 39 ; s mass and surface area . the surface coverage of lifepo 4 with dw was analyzed spectrophotometrically and found to be 0 . 5 nmol / cm 2 ( referred to the bet surface area of the electrode material ), which is ca . 3 molecules / nm 2 . this surface coverage is similar to that found for tio 2 ( vide ultra ) and also comparable to that reported for the bmabp / lifepo 4 system : 2 . 5 molecules / nm 2 . hence , the surface concentration of 2 - 3 molecules / nm 2 seems to be representative for monolayer coverage for these relatively small organic molecules with one phosphonic anchor . presumably , the gradual delithiation of lifepo 4 during repeated cycling from faster to slower scan rates might , actually , caused this effect too . also shown on fig7 a is the behaviour of a blank lifepo 4 film , which was not treated by dw . this electrode shows negligible electrochemical activity , as it is expected for a stoichiometric olivine , free from any carbon additives . the voltammogram of partly delithiated electrode also shows more clearly that the wiring current is independent of the scan rate . fig7 b presents the voltammogram of an electrode , which was delithiated by repeated cycling , followed by one - hour charging at a constant potential of 4 . 2 v . the total passed charge was equivalent to ca . 15 % of the theoretical charge capacity ( 170 mah / g ) of the used electrode . this electrode still exhibits the wiring effect , albeit the current for the 15 %- delithiated electrode is ca . 40 times smaller than for the fresh electrode . to get more insight into the fading of wiring activity , we have tested the behaviour of a fresh dw / lifepo 4 electrode during ten subsequent cv scans at various scan rates . fig8 summarizes the data for six electrodes ; each plot at the given scan rate starts from a virgin electrode , while care was taken that all six electrodes had roughly identical film mass and area (≈ 3 mg / cm 2 ). the molecular couple is still seen at the scan rate of 100 mv / s ( cf . fig7 and 8 ). at the scan rates of 50 and 20 mv / s , we can trace an almost ideal molecular wiring behaviour , which is also apparent at slower scanning of partly charged electrodes . nevertheless , slower scanning of a virgin electrode confirms that the wiring current drops significantly already at the time scale of cyclic voltammetry . fig9 shows potential - step chronoamperometry test of a virgin dw - wired lifepo 4 electrode . the current is not linear with t − 1 / 2 , in other words the cotrell - like behaviour is not traceable like for redox wiring of molecules on insulating supports ( tio 2 ). this is quite understandable , because in our case , the chronoamperometry is not controlled by diffusion , but by effects associated with the interfacial molecular wiring . consequently , chronoamperometry helps to evaluate the wiring effect itself . during one - hour of constant charging at 4 . 2 v , we can pass a charge equivalent to ca . 12 % of the total faradic capacity of the electrode material ( 170 mah / g ). this is more explicitly shown in fig9 - inset , where the current is expressed in a way conventional in battery testing . obviously , charging rates of ca . c / 2 - c / 10 are applicable for fresh electrodes and shallow charging . our data confirm that the wiring current is primarily controlled by the state of the dw / lifepo 4 interface , which is most easily described as the level of the lifepo 4 charging . this is further presented on fig1 , which compiles the data from cyclic voltammetry ( plots like those in fig4 and 5 ) and chronoamperometry ( fig9 ). voltammetric data ( points ) and chronoamperometry data ( line ) are reasonably matching . the wiring current seems to be roughly inversely proportional to the level of discharge , this is represented by a dashed line in fig9 . the performance of a dw - wired lifepo 4 olivine is far from that of the up - to - date carbon - coated lifepo 4 cathodes for li - ion batteries . but it is certainly interesting , at least academically , that a monolayer of molecules can carry currents , needed for charging of conventional batteries . we may reasonably expect further performance upgrade , if the particle size of the electrode material gets smaller . fig1 . vis - nir spectrum of the working solution of single wall carbon nanotubes dispersed by ru - complex , z - 907na / swcnt ( curve a ) and pure ru - complex z - 907na ( curve b ). the concentration of ru - complex was 6 × 10 − 4 mol / l in both cases , the optical cell thickness was 2 mm . fig2 . pure lifepo 4 electrode ( with 5 % pvdf ; total film mass 1 . 54 mg / cm 2 ) treated by dip coating into 6 · 10 − 4 mol / l solution of z - 907na ( left chart ) or z - 907na / swcnt ( right chart ). scan rates ( in mv / s ): 50 , 20 , 10 , 5 for curves from top to bottom . electrolyte solution is 1 m lipf 6 in ec / dmc . fig3 . left chart : cyclic voltammograms ( scan rates 0 . 1 mv / s ); electrolyte solution 1 m lipf 6 in ec / dmc . curve a : electrode from lifepo 4 surface - derivatized with z - 907na / swcnt ( 2 . 04 mg / cm 2 ). curve b ( dashed line ): electrode from carbon - coated lifepo 4 ( nanomyte be - 20 , 2 . 28 mg / cm 2 ). curve c : electrode from lifepo 4 surface - derivatized with pyrene butanoic acid / swcnt ( 1 . 83 mg / cm 2 ). the current scale is multiplied by a factor of 10 for curve b . right chart : galvanostatic charge / discharge cycle ; electrolyte solution 1 m lipf 6 in ec / dmc . curve a : electrode from lifepo 4 surface - derivatized with z - 907na / swcnt ( 2 . 04 mg / cm 2 ) charging rate c / 5 . curve b ( dashed line ): electrode from carbon - coated lifepo 4 ( nanomyte be - 20 , 2 . 28 mg / cm 2 ) charging rate c / 50 . fig4 : cyclic voltammograms of dw adsorbed on mesoporous tio 2 film . scan rates ( in mv / s ): 200 , 100 , 50 , 20 , 10 , 5 , 2 , 1 . inset shows the forward peak current as a function of the square root of the scan rate . fig5 : cyclic voltammograms of dw adsorbed on mesoporous tio 2 film . scan rate 1 mv / s . ten successive scans were accumulated . fig6 : cyclic voltammograms of dw adsorbed on limnpo 4 electrode . scan rates ( in mv / s ): 200 , 100 , 50 , 20 , 10 , 5 , 2 , 1 . inset shows the forward peak current as a function of the square root of the scan rate . fig7 : cyclic voltammograms of dw - wired lifepo 4 electrode . a : fresh electrode : first scan at 200 mv / s ( red ), 20 mv / s ( blue ). for comparison , green line is for lifepo 4 electrode without dw ( 20 mv / s ). b : used electrode ( after 15 % charge ): scan rates ( in mv / s ): 20 ( red ), 10 ( blue ), 5 ( green ), 2 ( black ), 1 ( magenta ). fig8 : cyclic voltammograms of dw - wired lifepo 4 electrode . ten successive scans were accumulated for each given scan rate . fig9 : potential - step chronoamperometry of dw - wired lifepo 4 electrode . the potential step was from 3 . 5 v to 4 . 2 v ( 3600 s ) to 3 . 5 v ( 300 s ). inset shows the same data recalculated in c - rate charging vs . charge capacity of the actual electrode assuming 170 mah / g as the theoretical charge capacity . fig1 : compilation of the measured wiring currents as a function of the level of charging assuming 170 mah / g ( theoretical charge capacity ) as the reference 100 % charge . points : data from cv at varying scan rates between 1 to 200 mv / s . curve : data from potential - 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