Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Patent
1995-06-05
1998-03-24
Tung, T.
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
260665R, 264109, 429232, H01M 460
Patent
active
057311072
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a polyacetylene-lithium insertion compound, more particularly usable as a negative electrode in a storage battery or electric accumulator.
Some years ago lithium electrochemical generators were developed due to their very high potential specific energy. These electrochemical generators comprise a positive electrode, a lithium ion-conducting liquid or solid electrolyte and a lithium-based negative electrode. Generally, the operation of these generators involves lithium intercalation and then deintercalation processes.
For the negative electrode, it is possible to use low potential insertion compounds for the lithium compared with the latter. Among the compounds of this type are known polyacetylene-lithium insertion compounds like those described by Fouletier et al in Solid State Ionics, 8, 1983, pp.165-168, Shacklette et al in J. Electrochem. Soc., vol.132, no.7, 1985, pp.1529-1535 and Jow et al in J. Electrochem. Soc., vol. 135, no.3, 1988, pp.541-548.
The polyacetylene-lithium insertion compounds described in the above documents are prepared electrochemically using an electrolyte in a solid or liquid organic medium.
Chemical processes for the preparation of lithium-doped polyacetylenes are known like those described by Murthy et al in Phys. Rev. B, Rapid Comm., vol.40, no.18, 1989, pp.12550-12553 and Leitner et al in Synth. Met., vol.28, 1989, pp.D225-D229.
The process described by Murthy et al consists of doping a polyacetylene film using an organic solvent containing a lithium compound, e.g. butyl lithium in hexane, phenyl lithium in a cyclohexane-diethyl ether mixture, or biphenyl lithium in 2-methyl tetrahydrofuran. The process described by Leitner et al consists of using a method for the vacuum evaporation of lithium on a polyacetylene film.
These processes are easier to put into effect than electrochemical processes, but do not make it possible to control the stoichiometry of the polyacetylene-lithium insertion compound obtained and in particular do not make it possible to saturate the polyacetylene with lithium in order to obtain at least the Li(CH).sub.6 stoichiometry.
The present invention relates to a process for the preparation of insertion compounds of the conjugate polymer-lithium type and in particular polyacetylene-lithium insertion compounds, which makes it possible to obtain higher lithium stoichiometries of the compounds.
The invention also relates to a polyacetylene-lithium insertion compound constituted solely by polyacetylene and lithium chains, characterized in that it contains at least six CH groups per lithium atom and in that it has a mono-clinic crystal structure.
Therefore this polyacetylene-lithium insertion compound is very interesting, because its high lithium content gives it much better electrical conductivity and electrochemical capacity or capacitance characteristics than those of the known, lithium-doped polyacetylenes.
When this insertion compound contains six CH groups per lithium atom, it has an electrical conductivity of approximately 250 S/cm.
Its crystal structure is also different from that of the known polyacetylene-lithium insertion compounds, which have been identified as being amorphous or belonging to the trigonal or hexagonal system.
Moreover, this insertion compound can be prepared by a simple, rapid and easily performable process requiring no difficult manipulations of often toxic solvents.
The invention also relates to a process for the preparation of a conjugate polymer-lithium insertion compound consisting of mixing a conjugate polymer with lithium and compressing the thus obtained mixtures.
The conjugate polymers usable in this process are polymers which can be doped by lithium such as polyacetylene, polyparaphenylene, poly(paraphenylene vinylene), poly(paraphenylene acetylene) and composite combinations of these polymers in substituted or unsubstituted form with dielectric polymers such as polystyrene, polyethylene and polypropylene.
For the performance of this process, the polymer and in particular polyacetylene can b
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J.Chem.Soc.Faraday Trans., vol. 80 (1984 month unavailable) pp. 2109-2118, "Electrochemistry of Polyacetylene, (CH)," Richard B. Kaner and Alan G. MacDiarmid.
Takeo Ito et al. "Simultaneous Polymerization and Formation of Polyacetylene Film on the Surface of Concentrated Soluble Ziegler-Type Catalyst Solution". Journal of Polymer Science, vol. 12, pp. 11-20. 1974 month unavailable.
K. Akagi et al. "Synthesis of Polyacetylene Films with High Density and High Mechanical Strength". Synthetic Metals, vol. 28, pp. D1-D10. 1989 month unavailable.
D. Begin et al. "Effects of the Stretching on the Crystalline Organization of Highly Oriented Trans Polyacetylene(HOPA)". Solid State Communications, vol. 76, No. 5, pp. 591-594. 1990 month unavailable.
Solid State Ionics, vol. 8, 1983 month unavailable, pp. 165-168, M. Fouletier, et al., "Lithium Intercalation in Polyacetylene".
Billaud Denis
Henry Fran.cedilla.ois Xavier
Willmann Patrick
Centre National d'Etudes Spatiales
Tung T.
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