TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The slurry composition further comprises conductive support agent as binder resin. Preferred Process: 100 parts mass active material, 5 parts mass conductive support agent, 2 parts mass binder resin, and 40 parts mass water are mixed to obtain slurry composition. The binder resin does not contain halogen element. The binder resin further comprises polymer (B) having structural units chosen from keto group-containing structural unit of formula (I) and (II), bivalent group-containing structural unit of formula: -(R15-O)- (III), and structural unit derived from compound of formula (IV). The bivalent group-containing structural unit (III) is of formula: =C(-R16)(-C(=O)-O-X11-R17) (V), =C(-R18)((-C=O)-O-X12-C(=O))-C(-R19)= (VI) or formula: A11-N=N-A12 (VII). The structural unit (II) and (III) has acidic group or its salt. The binder resin comprises component ( alpha ) and/or component ( beta ). The component ( alpha ) comprises polymer having structural unit of formula (VIII), and structural unit of formula (IX). The component ( beta ) comprises mixture of polymer ( beta 1) having structural unit (VIII) and polymer ( beta 2) having structural unit (IX).R11,R12,R21-R23=H, or 1-5C hydrocarbyl;R13,R17=H, or monovalent substituent;R14,R16=H, or methyl;R15,R31,R32=bivalent substituent;R33,A11,A12=monovalent substituent;s,t=0 or 1;andX11=bivalent substituent chosen from repeating unit of polyalkylene glycol, repeating unit of polyester diol, and repeating unit of polycarbonate diol.At least any 1 of R31 and R33 has vinyl structure. Preferred Process: The binder resin is obtained by hydrolyzing polymer ( beta 2). The binder resin and water are mixed, active material and conductive support agent are added and mixed, and viscosity of water is adjusted to obtain slurry composition. The slurry composition is coated to collector, dried and mixture layer having film thickness of 20-200 mu m is formed on the collector, to obtain electrode. The electrode is cut to 3 cm wide and 5 cm long, and set as test piece. The mandrel having diameter of 8 mm is applied to collector surface of test piece, and tape is fixed on one side of test piece. When a test piece is folded so that collector surface having humidity of 10% or less is observed, and flexibility of electrode is evaluated. When the flexibility test is carried out, there is no change in mixed layer is observed.