Composition for electrochemical device functional layer, functional layer for electrochemical device, and electrochemical device
Provided is a composition for an electrochemical device functional layer capable of providing an electrochemical device having low volume expansion. The composition for an electrochemical device functional layer contains a solvent and a polymer including an oxide structure-containing monomer unit. The oxide structure-containing monomer unit has a structure indicated by the following formula (I) (in formula (I), R 1 represents an optionally substituted alkylene group and n is a positive integer), and the polymer has a number-average molecular weight of not less than 5,000 and not more than 15,000.
1. A functional layer for an electrochemical device comprising: a polymer including an oxide structure-containing monomer unit, wherein
the functional layer does not include electrode active materials,
the functional layer further includes a binder,
the binder is at least one selected from a group consisting of a fluoropolymer, an aliphatic conjugated diene/aromatic vinyl copolymer, a hydrogenated product of an aliphatic conjugated diene/aromatic vinyl copolymer, an aliphatic conjugated diene/acrylonitrile copolymer, a hydrogenated product of an aliphatic conjugated diene/acrylonitrile copolymer, and a polyvinyl alcohol polymer,
the fluoropolymer is polyvinylidene fluoride,
the oxide structure-containing monomer unit has a structure indicated by a formula (I), shown below,
where, in the formula (I), R 1 represents an alkylene group or a substituted alkylene group and n is a positive integer,
the polymer further includes a monomer unit X other than the oxide structure-containing monomer unit,
the monomer unit X includes at least one of a (meth)acrylic acid alkyl ester monomer unit and a (meth)acrylonitrile unit,
the monomer unit X does not include a carboxy group-containing monomer unit, and
the polymer has a number-average molecular weight of not less than 5,000 and not more than 15,000.
2. The functional layer for an electrochemical device according to claim 1 , wherein R 1 is one selected from the group consisting of an ethylene group, a propylene group, and a phenylethylene group.
3. The functional layer for an electrochemical device according to claim 1 , wherein n is an integer of not less than 2 and not more than 30.
4. The functional layer for an electrochemical device according to claim 1 , wherein the polymer includes the oxide structure-containing monomer unit in a proportion of not less than 20 mol % and not more than 80 mol %.
5. The functional layer for an electrochemical device according to claim 1 , further comprising non-conductive particles.
6. The functional layer for an electrochemical device according to claim 1 , wherein the non-conductive particles include either or both of inorganic particles and organic particles.
7. An electrochemical device comprising the functional layer according to claim 1 .