NOVELTY - A solid ion conductor comprises garnet oxide (I), and boron trioxide.    USE - Solid ion conductor is used for solid electrolyte for all-solid-state lithium battery, lithium battery and lithium air battery (all claimed) for electric vehicles e.g. hybrid electric vehicles and plug-in hybrid electric vehicles, and large-scale storage batteries.    ADVANTAGE - The solid ion conductor has high ion conductivity, excellent low temperature properties, and improved energy efficiency.    DETAILED DESCRIPTION - A solid ion conductor comprises garnet oxide of formula: L5+x+2y(D'y,E3-y)(Mez,M2-z)Od (I), in which O is partially or totally substituted with pentavalent anion, hexavalent anion or heptavalent anion, and boron trioxide.    L=monovalent cation or divalent cation;    D'=monovalent cation;    E=trivalent cation;    Me,M=trivalent cation, tetravalent cation, pentavalent cation or hexavalent cation;    x+2y=0-3 (excluding 0);    y=0-0.5;    z=0-2 (excluding 2);and    d=0-12 (excluding 0).    INDEPENDENT CLAIMS are included for the following:    (1) lithium battery, which consists of a positive electrode (22) comprising a positive active material, a negative electrode (24) comprising a negative active material, and an organic electrolytic solution, in which positive electrode, negative electrode and/or organic electrolytic solution comprises the solid ion conductor;    (2) lithium air battery, which consists of a positive electrode, a negative electrode, a separator, and an ion conductive membrane comprising the solid ion conductor provided on surface of positive electrode, negative electrode and/or separator; and    (3) manufacture of solid ion conductor, which involves contacting precursors of garnet oxide, forming precursor mixture, calcining the precursor mixture, combining the calcined mixture and boron trioxide, and sintering the obtained mixture.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of all-solid-state lithium battery.    Positive electrode (22)    Positive active material layer (22b)    Negative electrode (24)    Negative active material layer (24a)    All-solid-state lithium battery (30)