WO2006051323A1

WO2006051323A1 - Polymer electrolyte

Info

Publication number: WO2006051323A1
Application number: PCT/GB2005/004372
Authority: WO
Inventors: Peter V. Wright; Yungui Zheng; Jianguo Liu
Original assignee: University of Sheffield
Current assignee: University of Sheffield
Priority date: 2004-11-15
Filing date: 2005-11-11
Publication date: 2006-05-18
Anticipated expiration: 2007-05-15

Abstract

A polymer electrolyte configured to provide ion transport, said polymer electrolyte comprising: a main-chain first repeating unit configured to provide a primary coordinating site for an ion, said first repeating unit being interdispersed between a main-chain second repeating unit to form an ion coordinating channel, said second repeating unit being less strongly ion coordinating than said first repeating unit; wherein said polymer electrolyte is configured to provide ion transport within said coordinating channel involving coordination and release of said ion by said primary coordinating site.

Description

POLYMER ELECTROLYTE

Field of the Invention The present invention relates to polymers and in particular, although not exclusively, to organised polymer electrolyte complexes configured for ion transport.

Background to the Invention Within the field of polymer electrolytes four distinct types of material, reflecting four different mechanistic approaches to ion mobility, have been recognised, i) The translation of lithium salts through liquid solvents in gels or 'hybrid' materials of various kinds, ii) Solvent-free, salt - polymer complexed systems in which the ion motion is coupled to the micro-brownian motion of segments of the polymer chains above the glass or melting transitions of the system, iii) 'Single-ion' systems, in which the lithium ion moves by a hopping process between anionic sites fixed to the polymer chain, or systems with reduced mobility of anions (solvent - containing or solvent -free), iv) Solvent- free, salt-polymer complexed systems in which ion mobility is uncoupled to the motions of polymer chain segments.

The drive towards solvent-free polymer electrolytes stems from the hazards associated with the highly reactive lithium (currently used within batteries) in contact with low-molecular weight solvents. This is especially apparent for heavy-duty> battery applications in which operation at elevated temperatures might be anticipated. Accordingly a very real risk of fire and explosion is to be associated with heavy-duty applications of such conventional lithium - organic solvent batteries.

Conventionally, solvent-free polymer electrolytes have been largely based upon complexes of lithium salts in amorphous forms of polyethylene oxide (PEO), this polymer dissolves lithium salts to give semi-crystalline or fully amorphous complex phases where ion migration through the amorphous phases gives rise to significant conductivity; M. B. Armand, in J. R. MacCallum, CA. Vincent (Eds) Polymer Electrolyte Reviews 1 , Elsevier, London, 1987, Chapter 1 ; .G.Cameron and M. D. Ingram, in J. R. MacCallum, CA. Vincent (Eds) Polymer Electrolyte Reviews 2, Elsevier, London, 1989, Chapter 5.; F. M. Gray, Polymer Electrolytes, the Royal Society of Chemistry, Cambridge, UK, 1997, Chapter 1. Ion mobilities in these systems are free-volume dependent and are essentially coupled to the segmental mobilities of the rubbery polymer, the conductivity, σ, generally following a strong temperature dependence. Whilst conductivities at temperatures above ca. 8O⁰C approach 10^"3 S cm^"1, which is adequate for successful operation of lithium batteries at such temperatures, a variety of strategies have thus far failed to bring about conductivities greater than ca. 10^"4 S cm^"1 at ambient temperatures (ca. 25⁰C).

In particular, the application of amorphous forms of PEO in ambient temperature batteries, requiring conductivities of ca. 10^"3 S cm^"1 is prohibited due to their low ambient conductivity. Other amorphous systems giving conductivities between 10^"4 to 10^'5 S cm^"1 have been proposed C A. Angell. C.

Liu and E Sanchez. Nature. 1993. 362. 137.; F. Croce. C. Appetecchi.L. Persi and B. Scrosati. Nature. 1998.394. 456.

In an attempt to address the low ambient temperature conductivities associated with PEO based electrolytes, various extended helical crystalline structures of PEO-alkyl salt complexes have been proposed forming organised low-dimensional polymer complexes, Y. Chatani and S. Okamura. Polymer. 1987 28. 1815.; P. Lightfoot. M. A. Mehta and P. G. Bruce. Science. 1993. 262.

883.; Y. G. Andreev. P. Lightfoot. And P. g. Bruce. J. Appl. Crystallogr., 1997.

18. 294; F. B. Dias. J. P. Voss. S. V. Batty. P. V. Wright and G. Ungar.

Macromol. Rapid Common., 1994. 15. 961.; F. B. Dias. S. V. Batty. G. Ungar.J.

P. Voss. And P. V. Wright. J. Chem. Soc, Faraday Trans., 1996. 92. 2599.; P. V. Wright. Y. Zheng. D Bhatt. T. Richardson and G. Ungar. Polym. Int., 1998.

47. 34.; Y. Zheng. P. V. Wright and G. Ungar. Electrochim. Acta. 2000., 45.

1161.; Y. Zheng. A Gibaud. N . cowlam. T. H. Richardson. G. Ungar and P. V. Wright. J Mater. Chem., 2000. 10. 69, Yungui Zheng, Fusiong Chia, Goran Ungar and Peter. V. Wright, Chem. Commun., 2000, 1459-1460.

Of these most recent solvent-free low-dimensional polymer electrolyte blends, a helical polymer backbone provides support for alkyl side-chains which interdigitate in a hexagonal lattice layer between the polyether helical backbones. Cations are encapsulated within the helices, one per repeat unit/helical turn, where the anions lie in the interhelical spaces. These three- component systems incorporate a long chain n-alkyl or alkane molecule, the inclusion of which provides increased conductivities resulting from highly- organised lamellar textures where the long chain n-alkyl or alkane molecule is embedded between lamellar layers.

However, such solvent-free polymer electrolyte complexes still exhibit unsatisfactory temperature dependent conductivities in addition to unsatisfactory conductivity levels at ambient temperature.

What is required therefore is a solvent-free electrolyte exhibiting reduced temperature dependent conductivities and/or increased conductivity at ambient temperature operating conditions.

Summary of the Invention

The inventors provide improved solvent-free polymer electrolytes capable of conductivities over the range 10^'4 S cm^"1 to 10^"2 S cm^"1 at ambient temperatures.

According to known solvent-free electrolyte complexes ion migration is provided via helical ionophilic polyether based coordinating channels, providing in turn, ion motion being largely de-coupled notwithstanding minimal local conformational motions of the polyether backbones. Following a realisation of enhanced ion mobility in such ionophilic channels, the inventors provide ionophilic coordinating pathways comprising oxygen-rich repeating units interdispersed between repeating units comprising less oxygens on the polymer backbones -A-

forming the ionophilic channels. When organised to form the coordinating channels, the oxygen-rich repeating units are configured to dissociate the metal salt by releasable coordination or complexing with the metal cation, in turn leaving the de-coupled anion aggregate within the ionophilic channels.

As the oxygen-rich repeating unit is interdispersed amongst the less coordinating repeating units, the conduction mechanism may be considered to be one of metal ion hoping along rows of de-coupled salt aggregates along the length of the conducting channels. Additionally, a mechanism for counter ion charge compensation within the channels may also be envisaged which does not constrain the facile cation hoping motion.

Therefore, by providing an ion conducting channel comprising regions configured to dissociate the metal cation from the salt, a polymer electrolyte is provided configured for enhanced ion mobility.

The inventors provide both a polymer electrolyte and a method of synthesising the same so as to provide a 'tuneable' polymeric self-organising ion conducting species configured to provide adjustable levels of ion conductivity, being dependent upon a ratio of the type and number of repeating units configured to complex the salt cation verses the type and number of repeating units making up the remaining part of the coordinating channel which is not configured to complex the metal cation and dissociate the salt.

Within the specification the term non-coordinating repeating units is a relative term to distinguish the oxygen-rich repeating unit configured to complex the metal cation and the repeating units which make up the majority of the coordinating channel, these later repeating units not being configured to dissociate the metal salt.

According to specific embodiments of the present invention the ratio of cation coordinating repeating units to non-coordinating repeating units may be greater or less being dependent upon the synthetic route employed. In particular, the polymer electrolyte may comprises a mixture of 15 to 25mol% coordinating repeating units and 75 to 85mol% of non-coordinating repeating units. For example, reactants, solvents and/or reaction parameters may be varied so as to achieve a desired ratio of coordinating repeating units to non-coordinating repeating units. Particularly, relative proportions of a co-solvent of dimethylsulphoxide (DMSO) and tetrahydrofuran (THF) may be varied. For example, variation of a type and/or molar quantity of a more polar solvent within a co-or multi-solvent system may be utilised in order to selectively synthesis a copolymer of desired coordinating sites to non-coordinating sites.

According to a specific implementation of the present invention ion coordinating channels are formed from polyether, polyester or polyether-ester backbones involving an oxygen-rich repeating unit, providing coordinating sites for the metal cation, being interdispersed within a relative oxygen-deficient repeating unit configured to coordinate cations to a lesser extent than the oxygen- rich repeating units.

Additional components within the polymer electrolyte complex may comprise a first and/or second ionic bridge polymer configured to enhance conductivity levels and reduce temperature dependent conductivity characteristics. In response to a de-blending heating process, the ion conducting polymer(s) establish a lamellar and/or micellar morphology, the ion coordinating channels being provided in such organised textures. This first and/or second ionic bridge polymer(s) sit(s) between the lamellar or micellar regions serving to provide an ionic bridge between amphiphilic channels so as to offset any reduction in conductivity resulting from ion conducting polymer lattice shrinkage in response to temperature reduction.

According to a first aspect of the present invention, there is provided a polymer electrolyte configured to provide ion transport, said polymer electrolyte comprising: a main-chain first repeating unit configured to provide a primary coordinating site for an ion, said first repeating unit being interdispersed between a main-chain second repeating unit to form an ion coordinating channel, said second repeating unit being less strongly ion coordinating than said first repeating unit; wherein said polymer electrolyte is configured to provide ion transport within said coordinating channel involving coordination and release of said ion by said primary coordinating site.

Preferably, said main-chain first repeating unit and/or said main-chain second repeating unit comprise a hydrocarbon side-chain extending from said main-chain repeating unit, said hydrocarbon side-chain being configured to interdigitate with hydrocarbon side-chains of neighbouring main-chain repeating units.

Preferably, said ion coordinating channel is oxygen-rich at said primary coordinating site; and said ion coordinating channel is oxygen-deficient in the region of said second repeating unit relative to said primary coordinating site.

Preferably, said main-chain first repeating unit comprises a plurality of methylene-oxy-methylene linkages and said main-chain second repeating unit comprises a plurality of methylene-oxy-methylene linkages, said main-chain second repeating unit comprising less methylene-oxy-methylene linkages than said main-chain first repeating unit.

Preferably, said main-chain first and second repeating units comprises alkylene ether linkages.

Preferably, said main-chain first repeating unit comprises between 4 to 8 oxyethylene linkages.

Preferably, said main-chain second repeating unit comprises between 1 and

3 oxyethylene linkages. Preferably, said main-chain first repeating unit comprises at least one ester linkage; at least one carbonate linkage and/or at least one ketone linkage.

said main-chain second repeating unit comprises at least one ester linkage; at least one carbonate linkage and/or at least one ketone linkage.

Preferably, said polymer electrolyte comprises a greater mole concentration of said main-chain second repeating unit relative to said main-chain first repeating unit.

Preferably, the interdigitated hydrocarbon side-chains are organized into crystal or liquid crystal ionophobic regions, said polymer electrolyte comprising a plurality of ion coordinating channels organized into ionophilic regions to form a polymer electrolyte lattice of ionophobic regions and ion conducting ionophilic regions.

Preferably, the polymer electrolyte further comprises a second polymer comprising ionophilic polyoxyalkylene units.

Preferably, the polymer electrolyte comprises a mixture of 15 to 25mol% of said main-chain first repeating unit and 75 to 85mol% of said main-chain second repeating unit.

Preferably, the polymer electrolyte further comprises a main-chain third repeating unit interdispersed between said first and second repeating units.

Preferably, said main-chain third repeating unit is less strongly ion coordinating than said first repeating unit.

Preferably, said main-chain third repeating unit comprises a single methylene-oxy-methylene linkage. Preferably, said main-chain third repeating unit comprises an ester linkage; a carbonate linkage and/or a ketone linkage.

Preferably, the polymer electrolyte further comprises a greater mole concentration of said main-chain second repeating unit relative to said main- chain first repeating unit; and a greater molar concentration of said main-chain third repeating unit relative to said main-chain first repeating unit.

According to a second aspect of the present invention there is provided a polymer comprising repeating units being represented by general formula (1) and (2):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or alkyl-phenyl and 8 ≥ n > 3, preferably n is 5 and 3 > r > 2, preferably r is 2.

Preferably, R¹ is a benzene nucleus or CH, R² is oxygen or CH₂, and R³ is a substantially straight chain hydrocarbon preferably -(CH₂)_m-H where 30 > m ≥ 5, more preferably m is 12, 16 or 18.

Preferably, said polymer comprises a combination of said straight chain hydrocarbon where m is 12 and 18.

Preferably, said polymer comprises a 50:50 mixture of Ci₂H₂₅ and C₁₈H₃₇ substantially straight chain hydrocarbon. Preferably, the polymer further comprises a repeating unit being represented by general formula (10):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or alkyl-phenyl and 8 > s ≥ 1.

Preferably, the polymer further comprises a repeating unit being represented by general formula (12):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or alkyl-phenyl.

Preferably, the polymer further comprises a repeating unit represented by general formula (11):

Preferably, wherein a molar amount of repeating unit (1) is less than repeating unit (2). Preferably, a molar amount of repeating unit (11) is greater than repeating unit (1) but less than repeating unit (2).

Preferably, the polymer further comprises a second polymer comprising repeating units being represented by general formula (3):

where A is alkylene or phenylene; B is alkylene, phenylene, alkylene ether, phenylene ether, alkylene-phenylene ether, alkoxy-phenylene ether or alkyl- phenylene ether; 40 > x > 20.

Preferably, A is (CH₂)t 6 > t ≥ 2; B is a substantially straight chain hydrocarbon preferably (CH₂)_m or B is -0-C₆H₄-O-(CH₂)_I2-O-C₆H₄-O-.

According to a third aspect of the present invention there is provided a polymer electrolyte being configured to provide ion transport, said polymer electrolyte comprising: a main-chain polyether repeating unit being configured to provide ion transport; an alkylene group or benzene nucleus being interdispersed within said polyether repeating unit; a hydrocarbon side-chain extending from said alkylene group or said benzene nucleus, said hydrocarbon side-chain being configured to interdigitate with hydrocarbon side-chains of neighbouring polyether repeating units; said polymer electrolyte characterised in that: said main-chain polyether repeating unit comprises between 1 to 3 oxyethylene linkages; wherein ion transport may be provided within a coordinating channel formed by said repeating unit.

Preferably, the polymer electrolyte further comprises a second main-chain polyether repeating unit comprising between 4 to 8 oxyethylene linkages interdispersed between said oxyethylene linkages of said main-chain polyether comprising between 1 to 3 oxyethylene linkages. Preferably, the polymer electrolyte further comprises a polyester repeating unit comprising between 1 to 8 oxyethylene linkages.

According to a fourth aspect of the present invention there is provided a polymer electrolyte being configured to provide ion transport, said polymer electrolyte comprising: a main-chain polyester repeating unit being configured to provide ion transport; an alkylene group or benzene nucleus being interdispersed within said polyester repeating unit; a hydrocarbon side-chain extending from said alkylene group or said benzene nucleus, said hydrocarbon side-chain being configured to interdigitate with hydrocarbon side-chains of neighbouring polyester repeating units; said polymer electrolyte characterised in that: said main-chain polyester repeating unit comprises between 1 to 8 oxyethylene linkages; said ion transport being provided within a coordinating channel formed by said repeating unit.

Preferably, the polymer electrolyte further comprises a main-chain polyether repeating unit comprising between 1 to 8 oxyethylene linkages interdispersed between said main-chain polyester repeating units.

Preferably, said polymer electrolyte is arranged as multilayers comprising ionophilic regions of polyester repeating units and ionophobic regions of hydrocarbon side-chains.

According to a fifth aspect of the present invention there is provided a polymer comprising a repeating unit being represented by general formula (2):

where R¹ is alkylene or a benzene nucleus; R² is oxygen or NH, alkylene, phenylene or CH₂; R i3 _: is alkyl, phenyl, alkyl-phenyl or hydrogen; and 3 ≥ r > 2. Preferably, the polymer further comprises an additional repeating unit being represented by general formula (1):

where 8 ≥ n > 3, preferably n is 5; wherein the formula (1) repeating units are interspersed between the formula (2) repeating units to form a mixed polyether skeletal sequence.

A galvanic cell is provided comprising a polymer, polymer electrolyte or polymer blend as described herein, and in particular the galvanic cell is configured as a solvent-free galvanic cell configured for use with lithium cations.

Preferably, the galvanic cell is configured for use with any one or a combination of the following anions:

CIO₄ ^", BF₄ ^", CF₃SO₃ ^" and/or (CF₃SO₂)N^"

According to a sixth aspect of the present invention there is provided a galvanic cell comprising a polymer electrolyte being formed from a first repeating unit being represented by general formula (10):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or alkyl-phenyl 8 > s ≥ 2, preferably s is 2.

Preferably, the galvanic cell further comprises a polymer electrolyte being formed from a second repeating unit being represented by general formula (12):

Preferably, the polymer electrolyte of the galvanic cell comprises a further repeating unit being represented by general formula (11):

R²-R³

-KHyfr (11)

Preferably, the polymer electrolyte of the galvanic cell comprises a further repeating unit being represented by general formula (2):

R²-R³

+^R1V^ (2) where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or alkyl-phenyl, and 3 ≥ r > 2, preferably r is 2.

Preferably, the polymer of said first repeating unit is positioned at or towards the cathode of said galvanic cell.

Preferably, the galvanic cell further comprises a second polymer comprising repeating units being represented by general formula (3):

where A is alkylene or phenylene, preferably (CH₂)t 6 ≥ t ≥ 2; B is alkylene, phenylene, alkylene ether, phenylene ether, alkylene-phenylene ether, alkoxy- phenylene ether or alkyl-phenylene ether;, preferably a substantially straight chain hydrocarbon, preferably (CH₂)m where 30 > m ≥ 5 or B is -0-C₆H₄-O-

(CH₂)_I2-O-C₆H₄-O- ; 40 > x > 20.

According to an seventh aspect of the present invention there is provided a process for the preparation of a polymer being represented by general formula (1):

where R¹ is alkylene or a benzene nucleus, R² is oxygen, alkylene, phenylene or CH₂; R³ is alkyl, phenyl, a substantially straight chain hydrocarbon preferably-(CH₂)_m-H where 30 ≥ m > 5, more preferably m is 12, 16 or 18; 8 ≥ n ≥ 2, said process comprising the steps of:

(a) reacting a compound being represented by general formula (7):

where Y is a halogen, preferably Br or Cl; with a compound being represented by general formula (8):

where 7 > p > 1. Preferably, the process further comprises a step of:

(b) reacting said compound of general formula (7) and general formula (8) with a compound being represented by general formula (9):

Preferably, wherein compounds (7), (8) and (9) are reacted in a DMSO solvent or a solvent mixture of DMSO:THF

According to an eighth aspect of the present invention there is provided a process for the preparation of a copolymer, said copolymer comprising repeating units being represented by general formula (1) and (2):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, alkylene, phenylene or CH₂; R³ is alkyl, phenyl, alkyl-phenyl, or a substantially straight chain hydrocarbon, preferably -(CH2)_m-H where 30 > m ≥ 5, more preferably m is 12, 16 or 18; 8 > n > 3 and 3 > r > 2.

said process comprising the steps of:

(a) reacting a compound being represented by the general formula (7):

where Y is a halogen, preferably Cl or Br; with a compound being represented by general formula (8):

where 7 > p ≥ 1.

According to a ninth aspect of the present invention there is provided a process for the preparation of a polymer electrolyte comprising the steps of:

(a) forming an ion conducting polymeric material having repeating units being represented by general formula (2):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, alkyiene, phenylene or CH2; R³ is alkyl, phenyl, alkyl-phenyl, or a substantially straight chain hydrocarbon, preferably -(CH₂)m-H where 30 ≥ m > 5, more preferably m is 12, 16 or 18, and 3 ≥ r > 2.

(b) heating said polymer electrolyte above a transition temperature.

Preferably, the process further comprises the steps of:

(c) prior to said heating step (b) blending compound (2) with a compound being represented by general formula (1):

where 8 > n > 2, preferably n is 5.

Preferably, the process further comprises step of:

(d) prior to said heating step (b) blending compound (2) with an ionic bridge polymer, said ionic bridge polymer being represented by general formula (3):

where A is alkylene or phenylene, preferably (CH₂)_t 6 ≥ t ≥ 2; B is alkylene, phenylene, alkylene ether, phenylene ether, alkylene-phenylene ether, alkoxy- phenylene ether or alkyl-phenylene ether;, preferably a substantially straight chain hydrocarbon, preferably (CH₂)_m where 30 > m > 5 or B is -0-C₆H₄-O- (CH₂)_I2-O-C₆H₄-O- ; 40 > x > 20.

Preferably, the process further comprises the step of:

(e) prior to said heating step (b) blending compound (2) and compound (1) with an ionic bridge polymer, said ionic polymer being represented by general formula (3):

where A is alkylene or phenylene, preferably (CH₂)_t 6 ≥ t ≥ 2; B is alkylene, phenylene, alkylene ether, phenylene ether, alkylene-phenylene ether, alkoxy- phenylene ether or alkyl-phenylene ether;, preferably a substantially straight chain hydrocarbon, preferably (CH₂)_m where 30 ≥ m > 5 or B is -0-C₆H₄-O- (CH₂)_I2-O-C₆H₄-O- ; 40 > x > 20.

Preferably, said second ionic bridge polymer is represented by the general formula (15):

where D is alkylene or phenylene, preferably (CH₂),-, where 5 ≥ r > 2, prefe jrraabbllyy r r i iss 44;; R R⁵⁵ i iss a allkkyyll,, p phheennyyll,, a a i straight chain or branched aliphatic hydrocarbon preferably C₁₈H₃₇; 40 ≥ s ≥ 20.

According to a further aspect of the present invention the polymer electrolyte comprises a repeating unit represented by general formula (13):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or alkyl-phenyl; R⁴ is an ester linkage, a carbonate linkage or a ketone linkage.

According to a specific implementation of the present invention the second ionic bridge polymer may be bonded to at least one end of the ion conducting polymer. For example, R⁵ of general formula (10) may be replaced with the repeating unit, being represented by general formula (2). Accordingly, the second ionic bridge polymer is maintained at the interface between the amphiphilic ion coordinating regions and the interdispersed first ionic bridge polymer.

Accordingly enhanced conductivity of the polymer electrolyte may be associated with the ionic bridge-ion conducting polymer hybrid species due to the even distribution of the second ionic bridge polymer at the interface with the first ionic bridge polymer. The bonding of the second ionic bridge polymer to the end units of the ion coordinating regions or channels may avoid a requirement to incorporate the separate and mobile second ionic bridge polymer in combination with the first ionic bridge polymer.

A possible synthetic route for the preparation of the above second ionic bridge polymer - ion conducting polymer hybrid species involves the preparation of the ion conducting polymer followed by introduction of the second ionic bridge polymer within a suitable solvent medium. The second ionic bridge polymer is therefore "tagged" onto the end of the ion conducting polymer following the polymerisation of the ion conducting polymer.

Brief description of the drawings For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which:

Fig. 1 illustrates schematically an organised, de-blended electrolyte complex;

Fig. 2 illustrates schematically an ion conducting channel within the electrolyte complex;

Fig. 3 illustrates schematically the electrolyte complex arranged as a lamellar texture;

Fig. 4 is a log conductivity vs 1/T plot for an electrolyte system according to a specific implementation of the present invention;

Detailed description of a specific mode for carrying out the invention There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description.

Within this specification the repeating units of the ion conducting polymer are represented by PO2-sc in the case of a main-chain second repeating unit configured to be non-coordinating with the metal cation and PO5-sc for a main- chain first repeating unit configured for coordination of the cation. According to specific implementations of the present invention PO2-sc comprises a single oxyethylene linkage within the repeating unit - optionally in addition to a hydrocarbon side-chain extending from the main-chain. PO5-sc comprises four oxyethylene linkages within the repeating unit (i.e. the main-chain repeating unit comprises five oxygens available for cation coordination) optionally in addition to a hydrocarbon side-chain. This nomenclature does in no way restrict the present invention to utilisation of an ion conducting polymer comprising these specific numbers of alkylene oxide linkages within repeating units of the main-chain. As will be appreciated by those skilled in the art, the present invention may include any number of alkylene oxide linkages within a repeating unit (single or plurality) forming part of the main-chain, in accordance with the teachings of the present invention.

Additionally, within this specification a first ionic bridge polymer is represented by 1 BP and a second ionic bridge polymer is represented by 2BP.

Referring to Figure 1 herein there is illustrated a schematic view of the polymer electrolyte comprising an ion conducting polymer 100 and a first ionic bridge polymer 101 , exhibiting an ordered morphology. Following a de-blending process, described below, the electrolyte system adopts a well-defined morphology where the ion conducting polymer is arranged in discreet lamellar or micellar regions, ion transport within such regions being provided by the amphiphilic main-chain first and second repeating units, PO5-sc and PO2-sc, respectively. Ionic bridge polymer 101 (1 BP or 2BP) provides a binding function being interdispersed between the micellar or lamellar regions. Ion transport therefore occurs between regions 100 and 101 where, for example, the electrolyte complex is provided between electrods of a battery.

Referring to Figure 2 herein there is illustrated a schematic view of a coordinating channel of the electrolyte system as detailed with reference to Figure 1 herein comprising PO5-sc repeating units 200; PO2-sc repeating units 201 ; hydrocarbon side-chain repeating units 202; metal cation 203; coordinating atoms 204; de-coupled anions 205; neutrally charged salt 206 and charged salt complex 208.

Following the de-blending process, described below, the electrolyte system adopts a well-defined morphology being arranged into ionophobic repeating unit regions involving an interdigitation of side-chains 202 as detailed with reference to Figure 3 herein, and ionophilic repeating unit regions or channels resulting from the organisation of main-chain first and second repeating units 200, 201. According to the specific implementation of the present invention the PO5-sc repeating units 200 are organised into substantially helical ion coordinating regions 200 within the channel predominately formed by the PO2-sc repeating units 201.

Accordingly, the mechanism for ion transfer and hence conductivity may be considered as extended cation hoping through the ionophilic channels via rows of de-coupled salt complexes.

By way of example and with reference to figure 2 herein, the conductivity mechanism may involve an initial separation or dissociation of the salt complex by coordination of the metal cation 203 by the main-chain first repeating unit comprising the five coordinating oxygens 200. This creates charge instability within the channel, in turn facilitating a cation jump 207 from the helical turn 200 onto a neighbouring salt aggregate 208. Charge compensation for the hoping cations may be provided by local ion migrations within channels or rows of separate anions and cations.

By providing a polymer backbone comprising ionophilic repeating units exhibiting little or no cation complexing characteristics together with interdispersed relatively strongly complexing units 200, a coordinating channel is provided configured to dissociate the salt complex whilst in turn providing a means by which this dissociated cation may travel along the channel.

1BP 101 acts as an ionic bridge or 'glue' between lamellar or micellar regions. According to specific implementations of the present invention a second ionic bridge polymer 2BP 206 is provided, acting as an interface between ion conducting polymer regions 100 and ionic bridge 101. Incorporation of 2BP increases the observed conductivity in addition to weakening the temperature dependence of conductivity.

Due to a relative motional freedom enjoyed by 1 BP and/or 2BP within the electrolyte system, on cooling the electrolyte an otherwise observed decrease in ion conductivity due to shrinkage and/or a freezing of the hydrocarbon ionophobic regions is offset by the 'glue'-like effect of the interdispersed 1BP and/or 2BP serving as an ionic bridge. Ion conductivity is therefore not substantially decreased following a decrease in temperature on passing through the melting and/or glass transition temperature of the interdigitated side-chains.

Referring to Figure 3 herein there is illustrated a schematic view of the electrolyte complex comprising a lamellar morphology the lamellar layers of ion conducting polymer 300 being separated by layers of 1 BP 301. As will be appreciated by those skilled in the art, following the de-blending process detailed below, interdigitation of the ionophobic hydrocarbon side-chains 202 and interaction between the metal salt and the ionophilic main-chain repeating units PO2-sc and PO5-sc provides an organised lamellar morphology. Incorporation of 2BP within the complex, may to serve to facilitate regular termination of the main-chains in turn promoting aggregation and a possible micellar morphology.

According to a second embodiment of the present invention ion transference is provided via ion coordinating channels comprising PO2-sc without incorporation or substantial incorporation of PO5-sc. A polymer electrolyte comprising a main-chain backbone of PO2-sc may provide mechanical advantages resulting from the increased chain rigidity. Electrolyte films of increased durability may therefore be provided in turn providing a more compact lightweight battery.

According to the second specific embodiment of the present invention 1BP and/or 2BP are utilised to maintain conductivity at ambient and reduced temperatures, such ionic bridge polymers serving to offset any temperature dependent conductivity effect on passing through the hydrocarbon side-chain melting and/or glass transition temperature(s).

According to further specific embodiments, the skeletal polymer backbone may comprise solely polyester or polyether-ester repeating units. Alternatively, the polyether-ester repeating units may be interdispersed amongst polyether repeating units.

In particular, the main-chain polymer backbone may comprise the polyester version of PO2-sc in which a carbonyl group is provided between the alkylene ether linkages and the hydrocarbon side chain. Additionally, the polymer electrolyte may be a block co-polymer of the ether and ester versions or may comprise a random mixture of the polyester and polyether versions of PO2-sc and/or PO5-sc.

There will now be described specific examples according to certain aspects of the present invention.

PO2-sc may be represented by specific formula (I):

PO5-SC may be represented by specific formula (II):

1BP may be represented by specific formula (III):

2BP may be represented by specific formula (IV):

Ci₈H₃₂ - O-|-(CH₂)₄ - OJ-C₁₈H_{37 (|V)}

The polyester may be represented by specific formula (V):

Referring to Figure 4 there is illustrated AC conductivities measured by complex impedance spectroscopy as a log σ vs 1/T plot for the ion conducting polymer formed as a copolymer of compounds (I) and (II): compound (III): compound (IV): LJBF₄ in molar ratios (1 :0.8:0.2:1.3). During an initial heating (de- blending process) up to ca. 100⁰C the conductivity rose steeply 400. On cooling 401 the conductivity remained high down to ambient temperature where following a second heating cycle 402 and cooling cycle 403, the conductivities remained high exhibiting reduced temperature dependence of the first heating cycle.

Accordingly, conductivities within the range 10^"2 to 10^"4 S cm^"1 have been observed with this system.

According to specific implementations of the present invention as a weight fraction the electrolyte system comprises 1 BP or 1 BP/2BP present as < ca. 50%.

Referring to Figure 4 herein the de-blending process establishing the lamellar or micellar morphologies is onset by initial heating cycle 400 the established morphology being maintained through the first and successive cooling cycles providing in turn enhanced electrolyte ion conductivities having reduced temperature-dependent characteristics.

DC polarisation measurements using lithium electrods gave ambient conductivities in the range 10^"3 to 10^"2 S cm^"1 in good accord with AC impedance measurements. Such DC conductivities thereby implying Li⁺ transport between electrods. Moreover, conductivities approaching 10^"2 S cm^"1 were observed at ambient temperature; such conductivities being established and maintained following an initial "electrolyte-ordering".

There will now be described specific preparations and examples to illustrate specific aspects of the present invention.

General preparation procedure for copolymer of (I) and (II) [example 1]

The copolymer of compound (I) and (II) was prepared in dry DMSO: THF co-solvent. By adjusting the relative proportions of DMSO to THF a tunable synthetic procedure is provided whereby a desired amount of main-chain first repeating units (compound (H)) and main-chain second repeating units

(compound (I)) are incorporated within the main-chain polymer backbone. In particular, increasing the amount of DMSO (being a substantially polar solvent) has the effect of increasing aggregation of the hydrocarbon side-chains thereby promoting synthesis of an ion conducting polymer being compound (I) rich.

Conversely, if the molar concentration of THF is increased, aggregation of the hydrocarbon side-chains is less and an ion conducting polymer having enhanced main-chain second repeating unit content (compound (II)) may be obtained.

General preparation procedure for copolymer of (I) and (II) [example 2]

Copolymers of compound (I) and compound (II) mixed polyether skeletal sequences were obtained from reactions involving appropriate molar proportions of the three types of monomer 5-alkyloxy~1,3-bis(bromomethyl)benzene, 5- alkyloxybenzene-1 ,3-dimethanol and tetraethylene glycol. For copolymers with greater proportions of compound (I) units a proportion of tetraethylene glycol was replaced by the alkyloxybenzene-1 ,3-dimethanol. However, the relative monomer proportions were determined by solubility considerations rather than stoichiometry owing to the amphiphilic nature of the side chain bearing monomers and the polymer product. The reaction also involved dehydration condensation between benzylic hydroxyls as well as the Williamson type condensations between hydroxyls and halogen functionalities. Copolymers with mixed alkyl side chains were readily prepared by mixing the appropriate side chain bearing monomers in the desired molar proportion. In this case the molar proportions in the monomer mixture are apparently reproduced in the polymer product in which they are presumably in random sequence.

Synthesis of 5-hydroxybenzene-1 ,3-dicarboxylic acid diethyl ester

36.5g (0.2mol) 5-hydroxyisophthalic acid, 150ml ethanol and 2ml concentrated sulphuric acid were refluxed for 3 hrs. The ethanol was removed under vacuum and the white crystals were washed with water and then dissolved in 200ml ethyl acetate. The solution was washed sequentially with aqueous sodium bicarbonate solution and water and finally dried over magnesium sulphate. After concentrating the solution under vacuum, white needles separated. The yield of 5-hydroxybenzene-1 ,3-dicarboxylic acid diethyl ester, m.p. 106°C, was 43.4g (91%). IR: 3291.4, 2985, 2907, 1804 - 1700, 1400-1250 cm -1

Synthesis of 5-hexadecyloxybenzene-1 ,3-dicarboxylic acid diethyl ester

16.5g (0.069mol) 5-hydroxybenzene-1 ,3-dicarboxylic acid diethyl ester, 21 g (0.069mol) 1-bromohexadecane and 120ml acetone were refluxed in the presence of 11.9g (0.086mol) potassium carbonate for 24 hrs. After addition of 100ml water, the solution was extracted with pentane. The pentane solution was washed with aqueous potassium hydroxide solution, water and then dried over magnesium sulphate. The solvent was evaporated under reduced pressure. The yield of 5-hexadecyloxybenzene-1 ,3-dicarboxylic acid diethyl ester, m.p.45°C, was 24g (75%). IR: 3042, 2935, 1724, 1608, 1501 , 1475 and 1251 cm^"1.

Synthesis of 5-hexadecyloxybenzene-i ,3-dimethanol

LiAIH₄ Ether '

15g (0.0325mol) 5-hexadecyloxybenzene-1 ,3-dicarboxylic acid diethyl ester was reduced using 3.1g (0.082mol) lithium aluminium hydride by refluxing in ethyl ether for 4 hrs. Ethyl acetate was added into the solution to decompose the remaining lithium aluminium hydride. The solution was poured into cooled 20% sulphuric acid. The mixture was extracted with chloroform. After drying over magnesium sulphate, the extract was evaporated under reduced pressure. The crude product was recrystallized from dichloromethane to afford white crystals.

The yield of 5-hexadecyloxy benzene-1 ,3-dimethanol, m.p.90°C, was 1Og (81%).

IR: 3256, 3060, 2917, 1600, 1472, 1150 and 1031 cm^"1. Elemental analysis, required: (%) C (76.19), 1-1(11.11 ); found: (%) C (76.07), H (11.40).

¹HNMR(CDCI₃) δ 0.85 (t, 3H), 1.25 (s 24H), 1.45 (5 peaks, 2H), 1.75 (5 peaks, 2H), 3.9 (t 2H), 4.65 ( d, 4H), 6.85 (s, 2H), 6.95 (s, 1 H).

Synthesis of 5-hexadecyloxy-1,3-bis(bromomethyl)benzene

5 g of 5-hexadecyIoxybenzene -1 , 3-dimethanol was suspended in 20 ml dry ethyl ether and stirred under a dry atmosphere and cooled down to 0⁰C. Into the suspension, 3.18g of phosphorous tribromide was added drop-wise, while keeping the temperature of the mixture below 5⁰C. After completion of the addition, the solution was allowed to warm up to room temperature and stirred for 10 hrs. The reaction mixture was then poured into a crushed ice bath, the separated organic layer was washed with a 10% sodium carbonate in water solution. The product was dried over anhydrous potassium carbonate and the solvents evaporated to yield white crystals. ¹H NMR(CDCI₃)δ: 0.85 (t, 3H), 1.25 (s, 28H), 1.45 (5 peaks, 2H), 1.75 (5 peaks, 2H), 3.95 (t, 2H), 4.40 (s, 4H), 6.85 (s, 2H). 6.95 (s, 1 H). Elemental analysis: Br, required 31.68%, found 31.49%.

Synthesis of compound (II)

Compound (II), was prepared by heating with gentle stirring at 3~50°C of 1g

(0.002mol) 5-hexadecyloxy-1 ,3-bis(bromomethyl)benzene, 0.385g (0.002mol) tetraethylene glycol, and 0.44g (0.008mol) potassium hydroxide in 1 ml dimethyl sulphoxide and 1 ml THF for 3 hours. The polymer was precipitated in water. The mixture was neutralized with concentrated acetic acid. The polymer was separated and washed with hot water 3 times to remove inorganic salt and finally with hot methanol 3 times to remove monomer. ¹H NMR(CDCI₃) δ: 0.85 (t, 3H), 1.25 (s, 28H), 1.75 (5 peaks, 2H), 3.65 (d, 15H), 3.95 (t, 2H), 4.50 (s, 4H), 6.80 (d, 3H). Hot stage microscopy indicates that the polymer melts at 27°C. The FTIR spectrum shows that the peak of OH group (3256 cm^"1) is not present. Synthesis of compound (I) [example 1]

Compound (I), was prepared as above but the molar equivalent of ethylene glycol was used. The yield was 64%. ¹H NMR: 5H(400MHZ; solvent CDCI₃; standard SiMe₄) 0.86 (3H, t, CH₃), 1.25 (25H, s, 12CH₂), 1.45 (2H, m, γ- CH₂), 1.75 (2H, m, β-CH₂), 3.65 (4H, s, 2 CH₂ ethoxy), 3.92 (2H, t, α-CH₂), 4.45 (4H, s, α-CH₂, benzyl), 6.85 (3H, m, C₆H₃aromatic). GPC molar mass averages M_n = 9,110, M_w = 74,063, M_z = 284,061. DSC of compound (I) indicates that the polymer melts at 37.76°C.

Synthesis of copolymer of (I) and (II) [specific example 1]

The copolymer was prepared by heating with gentle stirring at 70°C of 0.4g compound (II), 0.6g compound (I), 0.1g 1 , 3-bis (dibromomethyl) -5- hexadecyloxybenzene, and 0.045g potassium hydroxide in 1.8ml dimethyl sulphoxide for 3 days. The polymer was precipitated in water. The mixture was neutralized by addition of concentrated acetic acid. The polymer was separated and washed with hot water several times to remove inorganic salt and finally with hot methanol several times to remove monomer. The yield is 0.62g. The GPC gave molar mass averages M_n = 6,048, M_w = 29,746, M_z = 122,776. The polymer melts at 36°C.

Synthesis of copolymer of (I) and (II) variant [specific example 2]

Based on the procedure above [specific example 1] in the following example both types of copolymerisation skeletal chain and side chain were combined to give a copolymer of compound (I) and (II) having 50/50 molar mixture of -C₁₂H_2S and -Ci₈H₃₇ side chains and replacing the Ci₆ H₃₃ side chains of compounds (I) and (II). The different repeating units were mixed to give a copolymer comprising 80mol% of the compound (I) variant and 20mol% of the compound (II) variant.

Synthesis of "compound (III)

HO-[-(-CH₂-)₄.O-]_x-H ^B^_H ^Br > -{O-[-(-CH ₂-)₄-O-]_x-R-}_n-

*where _x ~ 23

where R= -(-CH₂-)-₁₂

*Compound (III) was prepared by standard Williamson condensation of hydroxy-terminated polytetrahydrofuran (M_n = 1688 g mol^"1) with 1 ,12- dibromododecane and excess powdered KOH (8 molar ratio) at 9O⁰C. *compound (III) was purified by washing with dilute aqueous acetic acid followed by water and dried under vacuum. . Gel permeation chromatography showed that <M_W> = 2.5 x 10⁴. IR: 2940cm^"1, 2859cm^'1 (CH₂ stretch) and 1113cm^"1 (C-O stretch). DSC of *compound (III) indicates that the polymer melts at 24°C.

Synthesis of ^compound (IV)

Ci₈H₃₇Br

H0-(- CH₂CH₂CH₂CH₂Q^ H >- C₁₈H₃₇CK-CH₂CH₂CH₂CH₂Q)- C₁₈H₃₇ ^x KOH ^x

*Where x is ~ 45.

*Compound (IV) was prepared by standard Williamson condensation of 8.44g (O.OOδmol) hydroxy-terminated polytetrahydrofuran (M_n = 1688 g mol^"1 ) with 3.33g (O.OOδmol) 1-bromododecane and excess powdered (8 molar ratio)

2.24g KOH in 40ml dimethyl sulphoxide for 7 days at 9O⁰C. *Compound (IV) was purified by washing with dilute aqueous acetic acid followed by water and dried under vacuum. The GPC result gave molar mass averages Mn = 3250; M_w = 4724. DSC of *compound (IV) indicates that the polymer melts over the range 10 - 35°C. IR 3482 (vOH), shoulder 3000-2950 (v-CH₃) 2923, 2798, 2740, (vCH₂)- 1110 (vC-O )

Synthesis of compound (V)

^(V>

5-hexadecyloxybenzene-1 ,3-dicarboxylic acid bis-(2-hydroxythyl)ester was heated at 200°C under vacuum to remove one ethylene hydroxide unit by ester interchange with a catalyst to catalyse polymerisation.

According to further specific implementations of the present invention, where higher molecular weight glycols are reacted with the dibromomethylebenzene, equal molar amounts of the glycol and the dibromomethylbenzene are reacted together.

Synthesis of diethyl 2-octadecyl propandioate, synthesis of diethyl 2- octadecyl propanedioate

After dissolving 2.3g of Na (0.1 mole) in 250ml anhydrous EtOH, 16g of diethylmalonate (0.1 mole ) was added dropwise under argon. After one hour at 50°C, 33.3g (0.1 mole) of 1 -bromooctadecane was added and the mixture stirred for 15h. The solution was concentrated to dryness and washed with hot CHCI₃. The precipitate of NaBr is filtered and the solution dried over MgSO₄. After evaporation, a yellow oil was obtained and distilled to give, 23g of diethyl 2- octadecyl propanedioate, yield 56%, bp: 185-190°C /0.04 torn Mp: 28°C. IR: 2918cm^'1 (CH₃ stretch), 2850cm^"1 (CH₂ stretch) and 1733cιτf¹ (C=O stretch).

Ref: M.V.D. Nguyen, M. E. Brik, B.N. Ouvrard, J. Courtieu, L. Nicolas and A. 5 Gaudemer, Bull. Soc. Chim. BeIg., 1996, 105(14), 181-3.

Synthesis of 2-octadecyl propane-1 ,3-diol

23g (0.056mol) diethyl 2-octadecyl propanedioate was reduced using 5.4g 0 (0.14mol) lithium aluminium hydride by refluxing in ethyl ether for 6 hrs. Ethyl acetate was added into the solution to decompose the extra lithium aluminium hydride. The solution was poured into cooled 20% sulphuric acid. Collect the white solid after ether was evaporated. Wash the solid with water, aqueous

K₂CO₃ solution and then water. After drying in an oven, the product was 5 extracted in dichloromethane using a soxhlet apparatus and evaporation of the solvent gave the pure white product. The yield of 2-octadecyl propane-1 ,3-diol, m.p.88°C, was 15g (81%).

Synthesis of aliphatic compound (II) variant

(L_N Br-fCH₂CH₂ CHkCH₂CH₂ Br | _o HCCH/ VOH NaH^/DMF 4_OC_{H H2} + _{OCH2 CH2} ^_n

1.64g (O.Oδmol) 2-octadecyl propane-1 ,3-diol and 0.24g (O.Oδmol) NaH were mixed under an argon atmosphere and 15ml DMF was added. The mixture was heated slowly with stirring to 90°C over 1 hour. 1.6g of tetraethyleneglycol di- bromide in 5ml DMF was added dropwise into the reaction and stirring was 5 maintained at this temperature for 1 day. A second portion of 0.24g NaH was then added and stirring continued at 90⁰C for a further 3 days. After the reaction mixture was cooled, water was added, followed acetic acid to neutralise the solution. The solid was separated by filtration and twice washed with water. The solid was precipitated from methanol. The aliphatic compound (II) variant, mostly melts at 45°C. ¹H NMR(400MHz, CDCI₃): δ=0.86(t, 3H, CH₃), 1.22 (s, 34H, alkyl chain 17CH₂), 1.75 (m, 1 H, CH), 3.60(t, 8H, OCH₂).

Synthesis of aliphatic version of compound (V)

The aliphatic ester version of compound (V) was synthesised according to the procedure detailed above for the aromatic ester. The reaction proceeds via ester interchange reaction with glycol in equal molar amounts to yield high molecular weight polyester according to the present invention.

Synthesis of poly[ 2-oxatrimethylene(5-hexadecyloxy-1 ,3-phenylene)] general formula (II)

The polymer represented by general formula (II) was prepared as above but the glycol was replaced by the molar equivalent of 5- hexadecyloxybenzene -1 , 3-dimethanol (i). The product is white and the yield was 63%. ¹H NMR: δ_H(400MHz; solvent CDCI₃; standard SiMe₄) 0.86 (3H, t, CH₃), 1.25 (25H, s, 12CH₂), 1.45 (2H, m, γ-CH₂), 1.75 (2H, m, β-CH₂), 3.92 (2H, t, α-CH₂), 4.45 (4H, s, OC-CH₂, benzyl), 6.85 (3H, m, C₆H₃aromatic). GPC molar mass averages M_n = 4,272, Mw = 10,594, M_z = 17,510. DSC of C16O1 indicates that the polymer melts at 40.92°C.

Alternative synthesis of general formula (II)

The polymer of general formula (II) was prepared by heating with gentle stirring at 6O⁰C of 1.00g (0.00264mol) 5- hexadecyloxybenzene -1 , 3- dimethanol, and 3g (0.04mol) potassium hydroxide in 5ml dimethyl sulphoxide for 7 days. The polymer was precipitated in water; the mixture was neutralized by addition of concentrated acetic acid and extracted into chloroform. After evaporation of the chloroform, the residue was washed with hot water several times to remove inorganic salt and finally with hot methanol several times to remove the monomer. ¹H NMR: δ_H(400MHz; solvent CDCI₃; standard SiMe₄) 0.86 (3H, t, CH₃), 1.25 (25H, s, 12CH₂), 1.45 (2H, m, γ-CH₂), 1.75 (2H, m, β- CH₂), 3.92 (2H, t, (X-CH₂), 4.45 - 4.9 (2H, s, Ct-CH₂, benzyl), 6.85 - 7.8 (3H, m, C₆H₃aromatic). FTIR showed a strong band at 1720 cm^"1. GPC molar mass average M_w =10,000. DSC of the polymer indicates that the polymer melts at 42⁰C.

Synthesis of poly[2,5,8,11 -tetraoxadodecamethylene(5-hexadecyloxy- 1,3-phenylene]

The polymer poly[2,5,8,11-tetraoxadodecamethylene(5-hexadecyloxy-1 ,3- phenylene] (100%) was prepared as above but the molar equivalent of Methylene glycol was used. The yield is (75%). ¹H NMR: δ_H(400MHz; solvent CDCI₃; standard SiMe₄) 0.86 (3H, t, CH₃), 1.25 (24H, s, 12CH₂), 1.45 (2H, m, γ- CH₂), 1.75 (2H, m, β-CH₂), 3.65 (12H, s, 6CH₂ ethoxy), 3.92 (2H, t, α-CH₂), 4.45 (4H, s, CC-CH₂, benzyl), 6.85 (3H, m, C₆H₃aromatic). GPC: molar mass averages M_n = 8,369, M_w = 21 ,555, M₂ = 39,720. DSC of the polymer indicates that the polymer melts at 28.07⁰C.

Synthesis of poly[2,5,8,-trioxanonamethylene(5-hexadecyloxy-1 ,3- phenylene

The polymer poly[2,5,8,-trioxanonamethylene(5-hexadecyloxy-1 ,3- phenylene (100%) was prepared as above but the molar equivalent of diethylene glycol, was used. The yield was 79%. ¹H NMR: 5H(400MHZ; solvent

CDCI₃; standard SiMe₄) 0.86 (3H, t, CH₃), 1.25 (25H, s, 12CH₂), 1.45 (2H, m, γ-

CH₂), 1.75 (2H, m, P-CH₂), 3.65 (8H, s, 4 CH₂ ethoxy), 3.92 (2H, t, α-CH₂),

4.45 (4H, s, α-CH₂, benzyl), 6.85 (3H₁ m, C₆H₃aromatic). GPC molar mass averages M_n = 8,174, M_w = 17,409, M₂ = 29,000. DSC of the polymer indicates that the polymer melts at 32.53⁰C. Synthesis of compound (lll)-derivatives-o-M- CH₂ - )— o-j- R-)-

L ³ Jx J

The above compound (lll)-derivative may be prepared by a ring opening cationic polymerisation. The cyclic ether may be cleaved with BF₃/dietherate so as to generate the required polyalkylene oxide. Such a process may similarly be employed for other similar compound (I I Invariants.

According to the compound (lll)-derivatives the R group is derived from a cyclic ether whereby copolymers may be synthesised involving cyclic ether ring opening polymerisations providing in turn high molecular weight polymers (M_w ca 10⁵). Where the compound (lll)-derivative comprises -(CH₂)₃- the cyclic ether derived R group may optionally comprise additional hydrocarbon side groups appended to the cyclic ether ring (for example methyl groups). Such side groups enhance the hydrophobic character of the polymer.

Specific examples of the compound (lll)-derivative copolymers comprise:

- [ - (CH₂)₃ - O - ] - [ - (CH₂)₄ - O - ] -; or

- [ - (CH₂)₃ - O - ] - [ - CH₂ - C(CH₃)₂ - CH₂ - O - ] -; where repeating units are randomly mixed. Moreover, the ionophobic character of the resulting polymer may be selectively adjusted by varying the relative amount of the cyclic ether containing at least one side group, during polymerisation of the above compound

(lll)-derivatives.

Accordingly and owing to the large polymer molecular weight distributions, electrolyte systems may be provided with enhanced mechanical properties being advantageous in the manufacture of batteries. Preparation of polyester, polycarbonate and polvether-ketone

Polyesters may be prepared by condensation of 5-hexadecyIoxybenzene -1 , 3-dimethanol with diacyl chlorides in basic media. The reaction would be performed with equimolar proportions of reagents in a solvent mixture such as THF/pyridine. Alternatively, the benzylic functions may be sufficiently reactive to support an interfacial mechanism.

base e.g. pyridine CIOC(CH ₂)_nCOCI ». + HCI

When the diacyl chloride is phosgene, a polycarbonate is obtained.

A polyether-ketone would be obtained from the Williamson condensation of equimolar proportions of 5-hexadecyloxy-1 ,3-bis(bromomethyl)benzene with dihydroxy acetone.

Electrolvte preparation

Complexes were prepared by mixing the ion conducting polymer with 1BP and/or 2BP together with appropriate molar proportion of Li salt, being selected from, for example, LiCIO₄, LiBF₄, LiCF₃SO₃, or Li(CF₃SO₂)N, in a mixed solvent of dichloromethane/acetone. After removal of solvent with simultaneous stirring complexes were dried under vacuum at 50°C-60°C.

An alternative preparation of the electrolytes may involve the known process of freeze-drying, following which the highly expanded polymer is collapsed as a powder and gently sintered below the de-blending temperature (ca. below 5O⁰C).

In particular, the inventors have devised a process for preparing and mixing the polymer electrolyte blend. This process involves the positioning of a rod, in particularly a glass rod, in a tube of larger diameter, in particular a glass tube. The polymer electrolyte is then placed between the rod and the tube whereby stirring of the rod provides a shearing of the polymer, with repeated turning providing complete mixing of the blend. To facilitate mixing further, the blend is typically heated at 5O⁰C.

Cell preparation

General

A galvanic cell utilising a polymer electrolyte according to the present invention comprises two electrods, an anode being lithium metal and a cathode being an inorganic particulate. For example lithium cobalt oxide or lithium manganese oxide, ceramic particles may be set in a matrix of the polymer electrolyte.

In order to allow the lithium to cross the interface between the electrolyte membrane and each electrod as a separated ion, a thin interface of an ion- separating polymer may be provided at each electrod. The ion-separating polymer, according to the present invention, may comprise for example polyethylene oxide or in particular PO5-sc. At the cathode the ion-separating polymer may be less than one micron in thickness (particle-particle distance). Additionally, a thin layer of identical or similar polymer configured for lithium ion separation may be applied at the lithium anode again, enabling the cation to cross the electrolyte-electrod interface. The ion-separating polymer may be applied to the electrod from a weak solution, in for example THF, before compiling the cell.

As reduction takes place at the anode, the inventors have realised that by locating at the anode a polymer electrolyte comprising predominantly polyether repeating units, according to the present invention, the electrolyte - anode junction does not degrade during use and charging of the galvanic cell.

As oxidation may occur at the cathode, the inventors have realised a requirement for a different type of electrolyte in contact with the inorganic, ceramic particles, this polymer electrolyte being stable to the inherent oxidative conditions of the cathode. One known attempt to address the problem of electrolyte degradation at the cathode involves coating the inorganic ceramic particles with lithium phosphate. Such coating may be used to coat the cathode of a galvanic cell according to the present invention.

In order to avoid the problems of electrolyte degradation at the cathode, the electrolyte material at the cathode may comprise a polyether-ester or a polyester. For example polyester compound (V) or the corresponding ester equivalent of PO5-sc, being stable to the oxidative conditions at the cathode, may be used.

For DC experiments, the Li electrods were prepared under an atmosphere of dry argon from Li pellets mounted in counter-sunk cavities (500 μm deep) in stainless steel strips. For AC experiments, cells having ITO electrods were prepared using polyester film laminated with low density polyethylene. Complex impedance measurements and DC polarisations were performed using a Solartron (RTM)

1287A electrochemical interface in conjunction with a 1250 frequency response analyser.

Metal alloys, in particular, lithium cobalt oxides, manganese oxides or tin based alloys may also be utilised within the cell as cathodic electrods being configured with a "binder" between particles and between electrod and electrolyte, the "binder" possibly being selected from any one or a combination of

PEO, PO1-SC, POδ-sc, P-nsc, 1 BP and/or 2BP.

In the freshly prepared cell the polymer electrolyte blend has low conductivity (~10^~9 S cm^"1) as shown in Figure 4 herein, so that in the early cycles only low currents (~10^"6 A) can be passed through the cell. The conductivity can be increased by raising the temperature but a requirement to raise the temperature of a lithium cell to 110° C would be both inconvenient and perhaps potentially damaging in creating high resistance interfaces at the electrod electrolyte interface. The potentiostatic DC (10-10OmV) runs with Li | polymer electrolyte | Li cells at temperatures 25-40° C indicated an apparent 'tracking' process in which the DC Li⁺ current brought about a progressive increase in conductivity eventually reaching the level of the AC impedance measurements between blocking electrods. At these temperatures lamellae of i/ncomplexed C1O5 segments are molten and those of C16O2 are close to melting. The C16O2 complexes undergo the crystal-liquid crystal transition a little higher at 42° C. The mechanism of tracking is therefore likely to involve the reorganisation of lamellae by melting and recrystallisation so that 'pathways of least resistance' are created. A similar mechanism may also be substantiated in the battery by passing a DC Li⁺ current. Furthermore, for electrods incorporating anisotropic particles it could ensure that pathways were created from the 'conducting face' of the particle and not from a planar 'non-conducting face' which might be the case with purely thermal annealing. In several potentiostatic (~3 V ) charging cycles at 30-40°C the inventors have observed the initial current to be on the order of 1 mA cm^'1 declining presumably by cell polarisation to a steady state at ca. 0.1 mA cm^"1. This suggests a 'leap' in conductivity from ~10^"9 S cm^"1 of the blend to ~10^"5 S cm^"1. Furthermore, the progressive decline over ca. 15 minutes is characteristic of a polarisation current involving ion migration and is not readily attributable to an electronic 'short' such as might arise from lithium dendrites. This is an encouraging indication that Li⁺ DC tracking might be a useful feature in these systems.

By allowing the lithium ions to establish the pathway of least resistance by passing the Li⁺ current through the electrolyte possibly involving a 'tunnelling' mechanism, at an elevated temperature and subsequently reducing the temperature to 'freeze-in' the established structure, the system is optimised to allow subsequent ion transport throughout life of the battery. Additionally, this 'tunnelling' of the Li⁺ ions at the lower temperatures of 25-40°C, may obviate the requirement to raise the temperature of the cell up to for example 110⁰C.

Claims

Claims:

1. A polymer electrolyte configured to provide ion transport, said polymer electrolyte comprising:

a main-chain first repeating unit configured to provide a primary coordinating site for an ion, said first repeating unit being interdispersed between a main-chain second repeating unit to form an ion coordinating channel, said second repeating unit being less strongly ion coordinating than said first repeating unit;

wherein said polymer electrolyte is configured to provide ion transport within said coordinating channel involving coordination and release of said ion by said primary coordinating site.

2. The polymer electrolyte as claimed in claim 1 wherein said main- chain first repeating unit and/or said main-chain second repeating unit comprise a hydrocarbon side-chain extending from said main-chain repeating unit, said hydrocarbon side-chain being configured to interdigitate with hydrocarbon side- chains of neighbouring main-chain repeating units.

3. The polymer electrolyte as claimed in claims 1 or 2 wherein said ion coordinating channel is oxygen-rich at said primary coordinating site; and

said ion coordinating channel is oxygen-deficient in the region of said second repeating unit relative to said primary coordinating site.

4. The polymer electrolyte as claimed in any preceding claim wherein said main-chain first repeating unit comprises a plurality of methylene-oxy- methylene linkages and said main-chain second repeating unit comprises a plurality of methylene-oxy-methylene linkages, said main-chain second repeating unit comprising less methylene-oxy-methylene linkages than said main-chain first repeating unit.

5. The polymer electrolyte as claimed in any preceding claim wherein said main-chain first and second repeating units comprises aikylene ether linkages.

6. The polymer electrolyte as claimed in any preceding claim wherein said main-chain first repeating unit comprises between 4 to 8 oxyethylene linkages.

7. The polymer electrolyte as claimed in any preceding claim wherein said main-chain second repeating unit comprises between 1 and 3 oxyethylene linkages.

8. The polymer electrolyte as claimed in any preceding claim wherein said main-chain first repeating unit comprises at least one ester linkage; at least one carbonate linkage and/or at least one ketone linkage; and

9. The polymer electrolyte as claimed in any preceding claim wherein said polymer electrolyte comprises a greater mole concentration of said main- chain second repeating unit relative to said main-chain first repeating unit.

10. The polymer electrolyte as claimed in any preceding claim further comprising:

a second polymer comprising ionophilic polyoxyalkylene units.

11. The polymer electrolyte as claimed in any preceding claim wherein the polymer electrolyte comprises a mixture of 15 to 25mol% of said main-chain first repeating unit and 75 to 85mol% of said main-chain second repeating unit.

12. A polymer comprising repeating units being represented by general formula (1) and (2):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH₁ alkylene, phen iyylleennee o orr C CHH₂₂;; R R³³ i iss a allkkyyll,, p phheenyl or alkyl-phenyl and 8 ≥ n > 3, preferably n is 5 and 3 ≥ r > 2, preferably r is 2.

13. The polymer as claimed in claim 12 wherein R¹ is a benzene nucleus or CH, R² is oxygen or CH₂ and R³ is a substantially straight chain hydrocarbon preferably -(CH₂)(_Ti-H where 30 > m ≥ 5, more preferably m is 12, 16 or 18.

14. The polymer as claimed in claims 12 to 13 further comprising a repeating unit being represented by general formula (10):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or alkyl-phenyl and 8 ≥ s ≥ 1.

15. The polymer as claimed in any one of claims 12 to 14 further comprising a repeating unit being represented by general formula (12):

(¹² )

16. The polymer as claimed in any one of claims 12 to 14 further comprising a repeating unit being represented by general formula (13):

17. The polymer as claimed in any one of claims 12 to 16 wherein a molar amount of repeating unit (1) is less than repeating unit (2).

18. The polymer as claimed in any one of claims 12 to 16 further comprising a second polymer comprising repeating units being represented by general formula (3):

where A is alkylene or phenylene; B is alkylene, phenylene, alkylene ether, phenylene ether, alkylene-phenylene ether, alkoxy-phenylene ether or alkyl- phenylene ether; 40 ≥ x ≥ 20.

19. The polymer as claimed in claim 18 wherein A is (CH₂)t 6 ≥ t ≥ 2; B is a substantially straight chain hydrocarbon preferably (CH₂)_m or B is -0-C₆H₄- O-(CH₂)₁₂-O-C₆H₄-O-.

20. A polymer electrolyte being configured to provide ion transport, said polymer electrolyte comprising:

a main-chain polyether repeating unit being configured to provide ion transport;

an alkylene group or benzene nucleus being interdispersed within said polyether repeating unit;

a hydrocarbon side-chain extending from said alkylene group or said benzene nucleus, said hydrocarbon side-chain being configured to interdigitate with hydrocarbon side-chains of neighbouring polyether repeating units;

said polymer electrolyte characterised in that:

said main-chain polyether repeating unit comprises between 1 to 3 oxyethylene linkages;

wherein ion transport may be provided within a coordinating channel formed by said repeating unit.

21. The polymer electrolyte as claimed in claim 20, wherein said hydrocarbon side-chain is alkyl, phenyl or a substantially straight chain hydrocarbon preferably -(CH₂)m-H where 30 > m ≥ 5, more preferably m is 12, 16 or 18.

22. The polymer electrolyte as claimed in claims 20 or 21 further comprising a second main-chain polyether repeating unit comprising between 4 to 8 oxyethylene linkages interdispersed between said oxyethylene linkages of said main-chain polyether comprising between 1 to 3 oxyethylene linkages.

23. The polymer electrolyte as claimed in any one of claims 20 to 22 further comprising a polyester repeating unit comprising between 1 to 8 oxyethylene linkages.

24. A polymer electrolyte being configured to provide ion transport, said polymer electrolyte comprising:

a main-chain polyester repeating unit being configured to provide ion transport;

an alkylene group or benzene nucleus being interdispersed within said polyester repeating unit;

a hydrocarbon side-chain extending from said alkylene group or said benzene nucleus, said hydrocarbon side-chain being configured to interdigitate with hydrocarbon side-chains of neighbouring polyester repeating units;

said polymer electrolyte characterised in that:

said main-chain polyester repeating unit comprises between 1 to 8 oxyethylene linkages;

said ion transport being provided within a coordinating channel formed by said repeating unit.

25. The polymer electrolyte as claimed in claim 24, wherein said hydrocarbon side-chain is alkyl, phenyl or a substantially straight chain hydrocarbon preferably -(CH₂)_m-H where 30 ≥ m ≥ 5, more preferably m is 12, 16 or 18.

26. The polymer electrolyte as claimed in claims 24 or 25 further comprising a main-chain polyether repeating unit comprising between 1 to 8 oxyethylene linkages interdispersed between said main-chain polyester repeating units.

27. A polymer comprising a repeating unit being represented by general formula (2):

R²-R³

-HΗvtf- (2)

where R¹ is alkylene or a benzene nucleus; R² is oxygen or NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl, alkyl-phenyl or hydrogen; and 3 > r > 2.

28. The polymer as claimed in claim 27 wherein R¹ is a benzene nucleus or CH, R² is CH₂ or oxygen and R³ is a substantially straight chain hydrocarbon preferably -(CH₂)_m-H where 30 ≥ m ≥ 5, more preferably m is 12, 16 or 18.

29. The polymer as claimed in claim 27 or 28 further comprising an additional repeating unit being represented by general formula (1 ):

where 8 > n > 3, preferably n is 5; wherein the formula (1) repeating units are interspersed between the formula (2) repeating units to form a mixed polyether skeletal sequence.

30. The polymer as claimed in any one of claims 27 to 29 further comprising an additional repeating unit being represented by general formula (10).

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or alkyl-phenyl 8 > s > 1.

31. The polymer as claimed in any one of claims 27 to 30 further comprising a repeating unit being represented by general formula (13):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phen iyylleennee o orr C CHH₂₂;; R R³³ i iss a allkkyyll,, p phheennyyll or alkyl-phenyl; R⁴ is an ester linkage, a carbonate linkage or a ketone linkage.

32. The polymer as claimed in any one of claims 27 to 30 further comprising a repeating unit being represented by general formula (12):

)

where R is alkylene or a benzene nucleus; R is oxygen, NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or alkyl-phenyl.

33. A polymer electrolyte comprising a repeating unit represented by general formula (13):

R²-R³

-^R U⁴-Ru¹-j-- ^{13) where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phen iyylleennee o orr C CHH₂₂;; R R³³ i iss a allkkyyll,, p phheennyyll or alkyl-phenyl; R⁴ is an ester linkage, a carbonate linkage or a ketone linkage.

34. A galvanic cell comprising a polymer electrolyte having a polymer with a repeating unit according to any preceding claim.

35. The galvanic cell as claimed in claim 34 configured for use with lithium cations.

36. A galvanic cell comprising a polymer electrolyte being formed from a first repeating unit being represented by general formula (10):

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or alkyl-phenyl 8 > s ≥ 1.

37. A galvanic cell comprising a polymer electrolyte being formed from a repeating unit being represented by general formula (12):

38. A galvanic cell comprising a polymer electrolyte formed from a repeating unit being represented by general formula (13): )

where R¹ is alkylene or a benzene nucleus; R² is oxygen, NH, alkylene, phen iyylleennee o orr C CHH₂₂;; R R³³ i iss a allkkyyll,, p phheennyyl or alkyl-phenyl; R⁴ is an ester linkage, a carbonate linkage or a ketone linkage.

39. A process for the preparation of a polymer being represented by general formula (1):

where R¹ is alkylene or a benzene nucleus, R² is oxygen, alkylene, phenylene or CH₂; R³ is alkyl, phenyl, a substantially straight chain hydrocarbon preferably-(CH₂)_m-H where 30 ≥ m > 5, more preferably m is 12, 16 or 18; 8 ≥ n > 2, said process comprising the steps of:

(a) reacting a compound being represented by general formula (7):

R²-R³

(7)

Y - CH₂ - R¹ - CH₂ - Y

where 7 > p ≥ 1.

40. The process as claimed in claim 39 further comprising a step of:

41. A process for the preparation of a copolymer, said copolymer comprising repeating units being represented by general formula (1) and (2):

R²-R³

+^yfr (2)

where R¹ is alkylene or a benzene nucleus; R² is oxygen, alkylene, phenylene or CH₂; R³ is alkyl, phenyl or a substantially straight chain hydrocarbon, preferably -(CH₂)_m-H where 30 ≥ m ≥ 5, more preferably m is 12, 16 or 18; 8 ≥ n > 3 and 3 > r > 2.

said process comprising the steps of:

(a) reacting a compound being represented by the general formula (7):

where 7 > p > 1.

42. The process as claimed in claim 41 further comprising a step of:

(b) reacting said compound of general formula (7) and general formula

(8) with a compound being represented by general formula (9):

43. A process for the preparation of a polymer electrolyte comprising the steps of:

where R¹ is alkylene or a benzene nucleus; R² is oxygen, alkylene, phenylene or CH₂; R³ is alkyl, phenyl, alkyl-phenyl or a substantially straight chain hydrocarbon, preferably -(CH₂)_m-H where 30 ≥ m > 5, more preferably m is 12, 16 or 18, and 3 > r > 2.

(c) heating said polymer electrolyte above a transition temperature.

44. The process as claimed in claim 43 further comprising the steps of:

(c) prior to said heating step (b) blending compound (2) with a compound being represented by general formula (1): R²-R³

+*Vth (1)

O

where 8 > n ≥ 2, preferably n is 5.

45. The process as claimed in claim 44 further comprising the step of:

where A is alkylene or phenylene, preferably (CH₂)_t 6 ≥ t ≥ 2; B is alkylene, phenylene, alkylene ether, phenylene ether, alkylene-phenylene ether, alkoxy- phenylene ether or alkyl-phenylene ether;, preferably a substantially straight chain hydrocarbon, preferably (CH2)_m where 30 > m ≥ 5 or B is -0-CeH₄-O- (CH₂)_I2-O-C₆H₄-O- ; 40 > x > 20.

46. The process as claimed in claim 44 further comprising the step of:

where A is alkylene or phenylene, preferably (CH₂)_t 6 ≥ t ≥ 2; B is alkylene, phenylene, alkylene ether, phenylene ether, alkylene-phenylene ether, alkoxy- phenylene ether or alkyl-phenylene ether;, preferably a substantially straight chain hydrocarbon, preferably (CH₂)m where 30 ≥ m > 5 or B is -0-C₆H₄-O- (CH₂)i₂-O-C₆H₄-O- ; 40 > x > 20.