(JP10116516-A)      A polymeric solid electrolyte comprises: a polymer matrix composed of a copolymer of a polymerisable monomer of formula H2C=C(R1)-C(=O)-N(R2)R3 (I) and a crosslinking agent of formula H2C=C(R4)-C(=O)-(OCH2CH2)n-O-C(=O)-C(R5)=CH2 (II); a polymerisation initiator; an electrolyte solution containing an inorganic salt and a solvent. In the formulae: R1, R4 and R5 = H or methyl; R2 and R3 = H, 1-6C alkyl, -(R)N(R')2 or -(R")OH; n = 3-30; and R, R' and R" = 1-6C alkyl.    Also claimed is a lithium secondary cell adopting the above polymeric solid electrolyte.    USE -   The polymeric solid electrolyte is useful in lithium secondary cells (claimed).    ADVANTAGE -   The polymeric solid electrolyte has good conductivity of at least 10-3 S/cm, can be easily processed due to its good mechanical properties, e.g. flexibility and plasticity, and has an good organic electrolyte solution capacity, i.e. does not leak organic electrolyte solution. When used in lithium secondary cells, the polymeric solid electrolyte provides improved operating voltage, lifetime and energy density.    (US5952126-A)      A polymeric solid electrolyte comprises: a polymer matrix composed of a copolymer of a polymerisable monomer of formula H2C=C(R1)-C(=O)-N(R2)R3 (I) and a crosslinking agent of formula H2C=C(R4)-C(=O)-(OCH2CH2)n-O-C(=O)-C(R5)=CH2 (II); a polymerisation initiator; an electrolyte solution containing an inorganic salt and a solvent. In the formulae: R1, R4 and R5 = H or methyl; R2 and R3 = H, 1-6C alkyl, -(R)N(R')2 or -(R")OH; n = 3-30; and R, R' and R" = 1-6C alkyl.    Also claimed is a lithium secondary cell adopting the above polymeric solid electrolyte.    USE -   The polymeric solid electrolyte is useful in lithium secondary cells (claimed).    ADVANTAGE -   The polymeric solid electrolyte has good conductivity of at least 10-3 S/cm, can be easily processed due to its good mechanical properties, e.g. flexibility and plasticity, and has an good organic electrolyte solution capacity, i.e. does not leak organic electrolyte solution. When used in lithium secondary cells, the polymeric solid electrolyte provides improved operating voltage, lifetime and energy density.