compositions and method for providing a solid conductive electrolyte composition containing a polyhydroxyalkanoate poly(hydroxyalkanoate) (PHA) and a salt of a conductive metal are described. The PHA is a biodegradable and biocompatible and provides a basis for batteries which are more environmentally degradable. Naturally occurring polymers including polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV) can be used to prepare the compositions.
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17. In a method for providing a solid conductive electrolyte composition has as a conductor, the improvement which comprises providing a polyhydroxyalkanoate poly(hydroxyalkanoate) polymer having repeating units selected from the group consisting of the formula: ##STR4## in admixture with a salt, where R is a lower alkyl and a lower alkenyl containing 1 to 10 carbon atoms and n is a number which produces a molecular weight between about 104 and 106.
1. A solid conductive electrolyte composition which comprises in admixture:
(a) a polyhydroxyalkanoate poly(hydroxyalkanoate) polymer having repeating units selected from the group consisting of the formula: ##STR3## wherein R is selected from the group consisting of a lower alkyl and a lower alkenyl containing 1 to 10 carbon atoms and n is a number which produces a molecular weight between about 104 and 106 ; and (b) a salt of a conductive metal, wherein the mole ratio of polymer to salt is between about 20 to 1 and 5 to 1.
33. In a battery including a thin film of an electrolyte composition between an anode and a cathode the improvement which comprises a solid conductive electrolyte composition which comprises in admixture:
(a) a polyhydroxyalkanoate poly(hydroxyalkanoate) polymer having repeating units selected from the group consisting of the formula: ##STR5## wherein R is selected from the group consisting of a lower alkyl and a lower alkenyl containing 1 to 10 carbon atoms and n is a number which produces a molecular weight between about 104 and 106 ; and (b) a salt of a conductive metal, wherein the mole ratio of polymer to salt is between about 20 to 1 and 5 to 1.
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This application was made with Government support under Grant No. NIH RO1GM33375 awarded by the National Institute of Health. The Government has certain rights in the invention.
(1) Field of the Invention
The present invention relates to solid conductive electrolyte compositions incorporating a branched LiClCO4 LiClO4
Preparation 2.
(a) 89% PHB/PHV copolymer, av MW 650,000.
PHV content 7% (Aldrich).
(b) 11% LiClCO4 LiClO4
Preparation 3.
(a) 89% PHB/PHV copolymer, av MW 650,000.
PHV content 24% (Aldrich).
(b) 11% LiClCO4 LiClO4
The conductivity at 41°C is recorded for Preparations 2 and 3 in FIG. 3. In FIG. 3, □ PHB/PHV 93% /17%; 93/7% ΔPHB/PHV 76%/24% MW >600,000. The mixture of PHV and PHB provided improved results where there is more PHV, thus indicating longer branches improve conductivity. The conductivity of preparation 1 at 41°C Was too low for measurement (<10-7 S/cm) at this temperature. At higher temperatures Preparation 1 would be conductive.
Following the procedure of Example 1, polymeric films of 600 μm were prepared using the following components (where the amounts are in mole percents):
Preparation 1.
(a) 89% PHB MW 30,000
(b) 7% LiClCO4 LiClO4
(c) 14% propylene carbonate
Preparation 2.
(a) 69% PHB MW 437,000 10% PHB MW 30,000
(b) 7%) LiClO4
(c) 14% propylene carbonate
Preparation 3.
(a) 79% PHB MW 437,000
(b) 7% LiClCO4 LiClO4
(c) 14% propylene carbonate
The time dependence of the dc conductivity at room temperature (24° C.) of preparations 2 and 3 is shown in FIG. 4. Preparation 1 conductivity was too low for measurement (<10-7 S/cm). In FIG. 4, ΔPHB ave MW 37,000 MW 437,000 □PHB ave MW 30,000. The results show that the low molecular weight PHB significantly improves the conductivity of the film. At higher temperatures Preparation 1 would be conductive.
Following the procedure of Example 1, polymeric films of 750 μm were prepared from the following components (where the percentages are in mole percent):
Preparation 1
(a) 77% PEO av MW 100,000
15% PEO av MW 8,000
(b) 8% LiClCO4 LiClO4
Preparation 2.
(a) 81% PHB av MW 30,000
(b) 8% LiClCO4 LiClO4
(c) 11% PEO av MW 100,000
Preparation 3.
(a) 42% PHB av MW 30,000
(b) 14% LiClCO4 LiClO4
(c) 44% PEO av MW 100,000
The time dependence of the dc conductivity at 24°C is shown in FIG. 5. Δ100K PEO 18K 84%/16%, ⊕30K PHB/100K PEO 80%/12%; ⊕30K PHB/100K PEO 49%/57%. The results show that PHB significantly improves the performance of PEO at high concentrations. The PHB with PEO makes a more amorphous composition.
It has been generally established that ion-conduction occurs in amorphous areas of a polymer and that the polymer solvent plays a very important role in the conduction process through local chain flexibility (Gray, F. M., "Solid polymer electrolytes" VCH pp 1-33 (1992)). Consequently, ion-conduction is restricted to temperatures above Tg (glass transition temperature) and below Tm (melting temperature). The aim of the present invention is to obtain a polyester with low crystallinity and low Tg with desirable mechanical properties (such as malleability). The great variability available in PHAs (such as different side chains, copolymers with different ratios and different molecular weight ranges), provides a large diversity of polymers with a range of Tgs and Tms from which to choose in designing polymer electrolytes that will conduct at any desired temperature range (Tg and Tm are generally discussed by Marchessault and Monasterios, Biotechnology and Polymers (Ed. C. G. Gebelein) Plenum Press, N.Y., pp. 47-52 (1991)). Added to this is the use of plasticizers--i.e. a low molecular weight, aprotic, polar molecule, such as propylene carbonate, ethylene carbonate and dimethylformamide, to improve conductance of complexes with too much crystallinity (the use of plasticizers is shown by Cowie, J. M. G., In "Polymer electrolyte reviews-I" (eds. J. R. MacCallum and C. A. Vincent) Elsevier Applied Science, New York, N.Y. pp. 69-101 (1987)).
The polymer can be modified to reduce crystallinity and average molecular weight by transesterification with α, Ω-diols containing 2 to 10 carbon atoms such as triethylene glycol or tetraethylene glycol to change the direction of the polymer from head to tail to tail to head. Thus high molecular weight (300,000 Dalton) PHB can be modified to reduce crystallinity and average molecular weight by transesterification with α, Ω-diols. This has been accomplished by using triethylene glycol or tetraethylene glycol (ca. 1:50 mole ratio with PHB) in refluxing dichloroethane solution, containing concentrated sulfuric acid as a catalyst. Following a 48 hour reaction period, these solutions were washed with sodium bicarbonate solution and brine, dried over anhydrous magnesium sulfate, and evaporated to a solid residue. This modified material was dried under vacuum at 100°C at 1 Torr for 24 hours. A H NMR 1 H NMR spectrum of this material shows incorporation of small amounts (ca. 2 %) of the polyether linker.
PHB average molecular weight <300,000 (Polysciences, Warrington, PA) melting point 175°-80°C 175°-180°C
PHB average molecular weight 30,000 (Polysciences, Warrington, PA) melting point 165°-167°C
PHB (300,000) treated with triethylene glycol (2% polyether linker) melting point 160°-165°C
The decline in melting point resulting from 2% crosslinking is greater than that realized by a tenfold decrease in molecular weight. This indicates that the cross-linked polymer is more amorphous. One can reasonably expect it to form more conductive salt complexes.
It is intended that the foregoing description be only illustrative of the present invention and that the present invention be limited only by the hereinafter appended claims.
Reusch, Rosetta N., Reusch, William H.
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