NOVELTY - Siloxanes comprising an 1,3-dioxolan-2-one-4-ylethyl substituent (I) are new.    USE - For electrochemical capacitors, e.g. electric double-layer capacitors, or lithium ion secondary batteries (claimed) used in laptop computers, mobile phones, digital cameras and digital video cameras, or as auxiliary power sources for electric and hybrid automobiles.    ADVANTAGE - The electrolytic solution enables construction of batteries and capacitors having improved discharge characteristics both at low temperatures and at high outputs and improved safety.    DETAILED DESCRIPTION - Cyclic carbonate-modified siloxanes of formula (I) are new, with the proviso that straight siloxanes containing less than or equal to 3 (R1ASiO2/2) units and cyclic siloxanes of 3-6 silicon atoms are excluded.    R1aAbSiO(4-a-b)/2 (I)    INDEPENDENT CLAIMS are also included for:    (1) a method for preparing a cyclic carbonate-modified siloxane, comprising subjecting to hydrolytic condensation a cyclic carbonate-modified silane of formula (5) or a hydrolysable silane mixture;    (2) a non-aqueous electrolytic solution comprising a non-aqueous solvent, electrolyte salt and (I);    (3) a secondary battery comprising the non-aqueous electrolytic solution;    (4) an electrochemical capacitor comprising the non-aqueous electrolytic solution; and    (5) a lithium ion secondary battery comprising the non-aqueous electrolytic solution.    R1= hydroxyl, or 1-30C alkyl, aryl, aralkyl, aminoalkyl, carboxyalkyl, alkoxy or aryloxy, which may be halo-substituted;    W=OH radicals, or alkyl, aryl, aralkyl, amino-substituted alkyl, carboxyl-substituted alkyl, alkoxy, or 1-30C aryloxy radicals optionally substituted with halo;    A=cyclic carbonate radical (2);    a=1-2.5;    b=0.001-1.5;    a+b=1.001-3;    R2=alkyl, aryl, aralkyl, amino-substituted alkyl, or 1-30C carboxyl-substituted alkyl radicals optionally substituted with halo;    R3=H, OH, alkoxy, aryloxy or halo;    p=0-2;    q=1-3; and    p+q=less than or equal to3.