NOVELTY - Mixture of polymerizable compounds, comprises: aromatic functional group containing polymerizable compound (a) or (b); phosphorus-containing functional group containing polymerizable compound (c); and highly polar functional group containing polymerizable compound (d).    USE - The mixture of polymerizable compounds or the polymer is useful in an electrolyte solution and an overcharge inhibitor for a lithium secondary battery (all claimed).    ADVANTAGE - The mixture of polymerizable compounds: enhances the safety of the battery when overcharged, without decreasing the performance of the battery; and provides overcharge inhibitor, which has high electrochemical stability within the operating voltage of a battery.    DETAILED DESCRIPTION - Mixture of poylmerizable compounds, comprises: aromatic functional group containing polymerizable compound of formula (Z1-X-A) (a) or (Z1-A) (b); phosphorus-containing functional group containing polymerizable compound (Z2-Y1) (c); and highly polar functional group containing polymerizable compound (Z3-W1) (d).    Z1-Z3 = polymerizable functional groups;    X = hydrocarbon or oxyalkylene having 1-20C;    A = aromatic functional group;    Y1 = phosphorus-containing functional group; and    W1 = highly polar functional group.    INDEPENDENT CLAIMS are also included for:    (1) a polymer of formula (-(Zp1-A)e-(Zp2-Y1)f-(Zp3-W1)g) (I) or (-(Zp1-X-A)e-(Zp2-Y1)f-(Zp3-W1)g) (II), where e, f, g are indicated by a unit of mol%;    (2) a lithium secondary battery, comprising a positive electrode (1), a negative electrode (2) and an electrolyte including the mixture of polymerizable compounds or the polymer;    (3) a lithium secondary battery containing a polymer formed by polymerizing the mixture of polymerizable compounds; and    (4) producing the polymer, comprising producing a mixture including both a polymerizable compound having an aromatic functional group and a polymerizable functional group and a polymerizable compound having a phosphorus-containing functional group that contains phosphorus and having a polymerizable functional group, and polymerizing the polymerizable compounds.    Zp1-Zp3 = residues of a polymerizable functional group;    e = greater than 0 to less than or equal to 100;    f = greater than 0 to less than 100; and    g = greater than or equal to 0 to less than 100.    DESCRIPTION OF DRAWING(S) - The figure shows a partial cross-sectional view illustrating a lithium secondary battery (a tubular lithium ion battery).    Positive electrode (1)    Negative electrode (2)    Battery can (54)    Negative electrode lead (55)    Positive electrode lead (57)