NOVELTY - A fluorocarbon polymer comprises repeated units containing triazole or tetrazole ring (RU(tria/tetra-zole)).    USE - A fluorocarbon polymer for composite used for solid electrolyte membrane and device e.g. electrolytic cell, fuel cell, flow battery, electric storage, electric generation device or water purification device (all claimed).    ADVANTAGE - Fluorocarbon polymer is stable and has high ion conductivity.    DETAILED DESCRIPTION - A fluorocarbon polymer comprises repeated units containing triazole or tetrazole ring (RU(tria/tetra-zole)) of formula (I).    Rf=-F and -CF3;    n=1 or 2;    Zf=direct bond, -CF2-, -CF2CF2- and -OCF2CF2-;    E,Q=C-R2 and N; and    R1,R2=H, SO3H, NO2, CN or monovalent (1-6C)hydrocarbon or bivalent (1-6C)hydrocarbon residue which taken together to form cycloalkyl or aromatic ring, or monovalent (1-6C)fluorocarbon, or bivalent (1-6C)fluorocarbon residue which are taken together to form cyclofluoroalkyl or fluorinated aromatic ring in which floating bond refers to covalent bond that attaches Zf group to C on triazole or tetrazole ring provided that C has total of four covalent bonds including the floating bond.    INDEPENDENT CLAIMS are included for:    (1) composite comprising 4-70 wt.% compound of formula H+n'XSUPERSCRIPTn'- and fluorocarbon polymer or 4-70 wt.% compound of formula M+n'YSUPERSCRIPTn'- and optionally support;    (2) solid electrolyte membrane comprising optionally solid support, and fluorocarbon polymer or composite in which total thickness of solid electrolyte membrane is 30-200 mu m and maximum tensile in machine direction for sheet processing (MD) and maximum tensile strength in transverse direction (TD) vertical to MD direction is greater than or equal to 20 MPa, preferably greater than or equal to 330 MPa under 50% relative humidity at 25 degrees C;    (3) fluorocarbon polymer comprising repeated units containing imidazole ring (RU(imidazole)) of formula (III) and optionally random or sequentially placed repeated units of tetrafluoroethylene (RU(TFE)) of formula (IV), or repeated units containing aniline ring (RU(aniline)) of formula (V) and optionally random or sequentially placed repeated units of tetrafluoroethylene of formulae (VI), (VII), (VIII) and (IX); and    (4) device comprising composite or solid electrolyte membrane.    n'=1-5;    XSUPERSCRIPTn'-,YSUPERSCRIPTn'-=negatively charged anion;    x=0-0.99;    1-x=0.01-1;    R3=R1;    RSUPERSCRIPTa-RSUPERSCRIPTd=R1;    R4,R5=H, R', -C(O)R', -S(O)R' and -S(O)2R';    R'=monovalent 1-6C hydrocarbon or bivalent 1-6C hydrocarbon residue;    Ar-=direct bond, di- or more substituted aromatic or heteroaromatic group having structure of formulae (Ar-1)-(Ar-5);    L=direct bond, -(CH2)m-, -(CH2O)m-, -(CH2CH2O)m- and -(CH2CH2NH)m-;    m=1-6;    na, nb, nc, nd, ne, nf=2 or 3;    J,J'=O or -NR'';    R''=H or 1-6C hydrocarbon; and    M+=H+, Li+, Cs+, Na+ or K+.