Encapsulated cathode active material particles, lithium secondary batteries containing same, and method of manufacturing

A particulate of a positive electrode active material for a lithium battery, said particulate comprising one or a plurality of positive electrode active material particles being embraced or encapsulated by a thin layer of a polymer having a recoverable tensile strain no less than 5%, a lithium ion conductivity no less than 10−6 S/cm at room temperature, and a thickness of the thin layer is from 0.5 nm to 10 μm, wherein said polymer contains an ultrahigh molecular weight polymer having a molecular weight from 0.5×106 to 9×106 grams/mole and said ultrahigh molecular weight polymer is selected from polyethylene oxide, polypropylene oxide, polyethylene glycol, polyvinyl alcohol, polyacrylamide, poly(methyl methacrylate), poly(methyl ether acrylate), a copolymer thereof, a sulfonated derivative thereof, a chemical derivative thereof, and combinations thereof, and wherein said lithium battery is selected from a lithium-ion battery or lithium metal battery, excluding metal-air and metal-sulfur battery.