A composition including a fluoropolymer and substantially free from a compound represented by the following formula (3): (H(CF.sub.2).sub.8SO.sub.3).sub.qM.sup.2, wherein M.sup.2 is H, a metal atom, NR.sup.5.sub.4, imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent; R.sup.5s are each H or an organic group and are the same as or different from each other; and q is 1 or 2.

An electrode comprising a space group Pna2.sub.1 VOPO.sub.4 lattice, capable of electrochemical insertion and release of alkali metal ions, e.g., sodium ions. The VOPO.sub.4 lattice may be formed by solid phase synthesis of KVOPO.sub.4, milled with carbon particles to increase conductivity. A method of forming an electrode is provided, comprising milling a mixture of ammonium metavanadate, ammonium phosphate monobasic, and potassium carbonate; heating the milled mixture to a reaction temperature, and holding the reaction temperature until a solid phase synthesis of KVOPO.sub.4 occurs; milling the KVOPO.sub.4 together with conductive particles to form a conductive mixture of fine particles; and adding binder material to form a conductive cathode. A sodium ion battery is provided having a conductive NaVOPO.sub.4 cathode derived by replacement of potassium in KVOPO.sub.4, a sodium ion donor anode, and a sodium ion transport electrolyte. The VOPO.sub.4, preferably has a volume greater than 90 ?.sup.3 per VOPO.sub.4.

A crosslinking agent includes a compound represented by the following formula (1).

##STR00001##

wherein R.sup.1, R.sup.2, and R.sup.3 are independently a hydrogen atom, a fluorine atom, an alkyl group, a fluoroalkyl group, or a substituted or unsubstituted aryl group, a plurality of R.sup.1 are identical to or different from each other, a plurality of R.sup.2 are identical to or different from each other, a plurality of R.sup.3 are identical to or different from each other, provided that at least one of R.sup.1, R.sup.2, and R.sup.3 is a hydrogen atom, and at least one of R.sup.1, R.sup.2, and R.sup.3 is a fluorine atom or a fluorine atom-containing group, m is an integer from 2 to 6, l is an integer from 0 to 2, and each hydrogen on the benzene ring(s) may be substituted.

A crosslinking agent includes a compound represented by the following formula (1).

##STR00001##

wherein R.sup.1, R.sup.2, and R.sup.3 are independently a hydrogen atom, a fluorine atom, an alkyl group, a fluoroalkyl group, or a substituted or unsubstituted aryl group, a plurality of R.sup.1 are identical to or different from each other, a plurality of R.sup.2 are identical to or different from each other, a plurality of R.sup.3 are identical to or different from each other, provided that at least one of R.sup.1, R.sup.2, and R.sup.3 is a hydrogen atom, and at least one of R.sup.1, R.sup.2, and R.sup.3 is a fluorine atom or a fluorine atom-containing group, m is an integer from 2 to 6, l is an integer from 0 to 2, and each hydrogen on the benzene ring(s) may be substituted.

The purpose of the present invention is to provide a redox flow secondary battery which has low electrical resistance and excellent current efficiency in addition to durability. The present invention relates to: an electrolyte membrane for redox flow secondary batteries, which contains an ion exchange resin composition containing a fluorine-based polymer electrolyte; and a redox flow secondary battery which uses the electrolyte membrane for redox flow secondary batteries.

The purpose of the present invention is to provide a redox flow secondary battery which has low electrical resistance and excellent current efficiency in addition to durability. The present invention relates to: an electrolyte membrane for redox flow secondary batteries, which contains an ion exchange resin composition containing a fluorine-based polymer electrolyte; and a redox flow secondary battery which uses the electrolyte membrane for redox flow secondary batteries.

An aqueous perfluoroelastomer dispersion and method for producing a perfluoroelastomer using a specific fluorosurfactant and capable of achieving a sufficient number of particles and a sufficient polymerization rate. The method includes providing an aqueous dispersion containing perfluoroelastomer particles by emulsion-polymerizing a perfluoromonomer in an aqueous medium in the presence of a specific fluorosurfactant in an amount of 2 parts by mass or more for 100 parts by mass of the aqueous medium.

An aqueous perfluoroelastomer dispersion and method for producing a perfluoroelastomer using a specific fluorosurfactant and capable of achieving a sufficient number of particles and a sufficient polymerization rate. The method includes providing an aqueous dispersion containing perfluoroelastomer particles by emulsion-polymerizing a perfluoromonomer in an aqueous medium in the presence of a specific fluorosurfactant in an amount of 2 parts by mass or more for 100 parts by mass of the aqueous medium.

This invention pertains to fluoroallylsulfonyl azide compounds of formula: CF.sub.2CFCF.sub.2R.sub.fSO.sub.2N.sub.3 formula (I) wherein R.sub.f is a divalent (per)fluorinated group, optionally comprising one or more than one ethereal oxygen atom [monomer (Az)], which are useful as functional monomers in fluoropolymers, to the fluoropolymers which comprise recurring units derived from such fluoroallylsulfonyl azide compounds, to a process for their manufacture, to a curable compound comprising the same and to a method for crosslinking the same.

This invention pertains to fluoroallylsulfonyl azide compounds of formula: CF.sub.2CFCF.sub.2R.sub.fSO.sub.2N.sub.3 formula (I) wherein R.sub.f is a divalent (per)fluorinated group, optionally comprising one or more than one ethereal oxygen atom [monomer (Az)], which are useful as functional monomers in fluoropolymers, to the fluoropolymers which comprise recurring units derived from such fluoroallylsulfonyl azide compounds, to a process for their manufacture, to a curable compound comprising the same and to a method for crosslinking the same.