Ionic rubber, polymer electrolytes

Poly(styrene-co-butadiene) rubber and poly(acrylonitrile-co-butadiene) rubber latex mixture films were evaluated as precursors of polymer electrolytes. A 50 50 blend was the optimum for mechanical strength and ionic conductivity. A simple equivalent mechanical model for the relationship between the mechanical strength and the structure was developed, which gave good agreement with experimental results, including materials with co-continuous phase morphologies. 26 refs. 

An ionic rubber comprising a low-temperature molten salt mixture and a small amount of high-molecular-weight polymer. On a structural level, these electrolytes have some features in common with gel electrolytes. They were first reported in the literature in 1993 [5] and are in the early stages of development. 

O.2UCIO4 is added with a small amount of polymer such as PPO and lithimn poly(lithium vinyl sulfonate), an ionic rubber that can transfer ions is obtained, with an ionic conductivity of 1(T S/cm at room temperature. However, the electrochemical window of the prepared ionic liquid currently is limited to about 3.5 V. As a result, the applications for the obtained gel polymer electrolyte are also limited and cannot meet the demands of high-voltage Uthiiun-ion batteries. 

Among the polymer electrolytes obtained from natural polymers, Klink-lai et reported ionic conductivity and NMR spectroscopy of polymer electrolytes formed by the mixture of liquid epoxidized natural rubber with Uthium salts. The authors discussed the correlation between the spin-lattice relaxation times with the solubility of the different lithium salts in the deprotonized liquid rubber. Based on the NMR chemical shift and the resonance half-width and the spin-lattice relaxation times results they concluded that lithium bis(trifiuoro methane sulfonyl)imide is a suitable salt for forming polymer electrolytes with deprotonized liquid natural rubber. 

Various workers have studied electrol5des made by blending ionic liquids with solvents [3536,43,51,61-63], polymer electrolytes [26,48303538,64-68], polymers as electrode binders [21,4833,69] and ionomers whereby elements of the ionic liquids are incorporated into the pol)rmer backbone [70-75]. Such work has opened up new fields for these materials and simultaneously blurred the distinctions among ionic liquids, and rubber, glassy, gel, ionomer and polymer electrolytes. This is exemplified by a complex scheme in a review by AngeU [26]. hi this chapter, we have included such materials only when the salt forms the major component of the electrolyte, such as polymer-in-a-salt electrolytes or PISE [76,77]. 

It is known that plasticized rubber, which is made of a copolymer of PVDF and HFP and impregnated with electrolyte solution, shows high ionic conductivity [37]. Thus by increasing the ratio of HFP to PVDF, the ionic conductivity and processability can be improved. A research team as Bellcore Co. Reported that if the HFP content is increased in the HFP/PVDF copolymer used as the polymer matrix, the melting point of the copolymer decreases. At 12% HFP, the copolymer can be processed at 120 to 130°C. A gel is prepared using an electrolyte composition of 1 mol/fLiPFg/EC/DMC, and this gel electrolyte was used for the 4-V... 

In addition, polymers with free carboxylic acid groups such as PAA and poly(methacrylic acid) can form copolymer electrolytes with PEO, leading to a sharp increase in ionic conductivity. Apparently, the PAA or other polycarboxylic acids can increase the lithium-ion transference number by decreasing the transfer of anions. The ionic conductivities of these copolymer electrolytes can be further increased by adding boron trifluoride diethyl etherate (Bp30Et2), which can promote the dissolution of lithium cations and carboxylic acid anions. Epoxidized natural rubber can also increase the ionic conductivity of PEO. Addition of symmetric poly(styrene-Wocfc-ethylene oxide) copolymers obviously affects the distribution of Lb ions. In contrast to current solid and liquid electrolytes, its ionic conductivity increases with increasing molecular weight of the copolymers. 

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