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), Rrepresents 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.