NOVELTY - A positive mix layer containing lithium-containing complex oxide is supported on a positive-electrode collector to form a positive electrode. The positive electrode is washed with a washing liquid containing organic boranes and an aprotic solvent.    USE - Manufacture of positive electrode for nonaqueous electrolyte secondary batteries (claimed) e.g. lithium ion battery and polymer electrolyte secondary battery used as power supply of electronic devices and vehicles, and for electric power storage. Uses include but are not limited to mobile telephones, personal digital assistants, notebook personal computers, digital cameras, handheld game machines, electric vehicles, hybrid vehicles, and aircraft.    ADVANTAGE - The method enables manufacture of positive electrodes which improve cycle characteristics, storage characteristics, and reliability of nonaqueous electrolyte secondary batteries, by suppressing inclusion of lithium hydroxide and lithium carbonate during production.    DETAILED DESCRIPTION - A positive mix layer containing lithium-containing complex oxide of formula: LixMyM'e1-yO2+d, is supported on a positive-electrode collector to form a positive electrode. The positive electrode is washed with a washing liquid containing organic boranes and an aprotic solvent. The organic boranes are of formula: BR1R2R3.    R1-R3=aryl or alkyl (both optionally substituted by fluoro);    M=Ni, Co and/or Mn;    M'e=metallic element different from M;    x=0.98-1.1;    y=0.9-1;and    d=portion for oxygen defect or surplus oxygen.    An INDEPENDENT CLAIM is included for nonaqueous electrolyte secondary battery consisting of the positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and a nonaqueous electrolyte containing the organic boranes.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the nonaqueous electrolyte secondary battery.    Electrode group (1)    Battery case (2)    Insulation board (7)    Insulation packing (8)    Safety valve (10)