ELECTROLYTE, ELECTROCHEMICAL DEVICE, LITHIUM-ION SECONDARY BATTERY, AND MODULE

An electrolyte solution containing a compound represented by formula (1) and a compound represented, for example, by formula (11-1), the formula (1) being: wherein Mis P or P═O; Ris a group such as a C1-C11 alkylsilyloxy group; n101 is an oxidation number of Mminus 1 or an oxidation number of Mminus 3; and Rto Rare each individually a group such as a C1-C11 alkyl group; the formula (11-1) being: wherein Rand Rare the same as or different from each other and are each an atom or group such as a hydrogen atom; and Ris a group such as an alkyl group free from a fluorine atom.