The invention relates to a half-cell including an electrode formed of an electron collector containing one or more transition metals from groups 4 to 12 of the Period Table of the Elements, and of an electrochemically active material present on the surface of the electron collector in the form of a nanostructured conversion film containing nanoparticles having an average diameter of between 1 nm and 1000 nm. The electrochemically active material contains at least one compound of the transition metal or the transition metals present in the electron collector. The invention further includes a continuous film of a lithium-ion conductive, solid electrolyte that is water- and air-impermeable and that is deposited directly onto, covering totally, the surface of the nanostructured active material of the electrode. The continuous film of solid electrolyte having a thickness of between 1 μm and 50 μm.