Abstract: A lithium ion-conductive solid electrolyte consisting of a compound represented by the chemical formula, Li.sub.1+x M.sub.x Ti.sub.2-x (PO.sub.4).sub.3 (M is at least one element selected from the group consisting of Fe, Al and rare earth elements and x is a number of 0.1 to 1.9), a compound represented by the chemical formula, Li.sub.1+y Ti.sub.2 Si.sub.y P.sub.3-y O.sub.12 (Y is a number of 0.1 to 2.9), or a compound obtained by mixing a compound represented by the chemical formula, LiTi.sub.2 (PO.sub.4).sub.3 with a lithium compound other than LiTi.sub.2 (PO.sub.4).sub.3 and sintering the resulting mixture. Said lithium ion-conductive solid electrolyte can be produced by subjecting to solid phase reaction a mixture of a titanium oxide, a lithium salt, a phosphoric salt and M.sub.2 O.sub.3 (M is at least one element selected from the group consisting of Fe, Al and rare earth elements) or a silicon oxide or a mixture of LiTi.sub.2 (PO.sub.4).sub.3 and other lithium compound.

Abstract: A solid electrolyte sheet comprising an ion-conductive inorganic solid electrolyte and an insulating elastomer, wherein the inorganic solid electrolyte powder is uniformly dispersed in the insulating elastomer in a volume fraction of 55-95% and which sheet has a hardness (ASTM A) of 65-96 and a thickness of 10-250 .mu.m, or a solid electrolyte sheet comprising a non-conductive reticulate material and a mixture of an ion-conductive inorganic solid electrolyte powder and an insulating elastomer, in which mixture the solid electrolyte powder is uniformly dispersed in the insulating elastomer in a volume fraction of 55-95%, at least the openings of the reticulate material being filled with said mixture. Said solid electrolyte sheets are superior in ion-conductivity, processability, productivity, storage stability and flexibility and are suitable for use in thin and large electrochemical elements.

Abstract: A structure comprising a pair of electrode sheets and an electrolyte sheet, the latter being sandwiched in between the former, wherein each of the pair of electrode sheets comprises a mixture comprising an insulating elastomer and an electrode active substance powder and/or an inorganic solid electrolyte powder, in which mixture the electrode active substance powder and/or the inorganic solid electrolyte powder are dispersed in a volume fraction of 75-95% in the insulating elastomer, and said electrolyte sheet comprises a mixture of an inorganic solid electrolyte powder and an insulating elastomer and optionally an electrode active substance powder, in which mixture the inorganic solid electrolyte powder and optionally the electrode active substance powder are dispersed in a volume fraction of 55-95% in the insulating elastomer. Each of said electrode sheet and said electrolyte sheet may further comprise a reticulate material sheet, the openions of which are filled with the mixture.