NOVELTY - The cell/battery has a negative electrode material comprising a composite of tin and silicon in which the tin and silicon are present in separate phases. The composite of tin and silicon accepts insertion of lithium during charging of the cell or battery and releases lithium during discharge of the cell/battery. The composite of tin and silicon is characterized by nanoscale islands of amorphous silicon phase dispersed in a matrix phase of tin. The composite of tin and silicon is an adherent film of tin and silicon sputtered onto a surface of metal current collector for the material.    USE - Lithium-sulfur secondary electrochemical cell/battery for powering electric traction motors in electric and hybrid electric vehicles i.e. automotive vehicles.    ADVANTAGE - The cell/battery enables a microstructure to provide the tin phase, which is electrically conductive and electrons to reach island-like silicon phase particles. The cell/battery facilitates diffusion of lithium in tin being much faster than in silicon so as to reduce concentration gradient of lithium ions through larger composite particles of silicon and tin, thus reducing the diffusion induced stress to mitigate fracture of the larger composite particles. The cell/battery allows a relatively soft tin matrix to absorb the elastic strain energy and prevent the micro-cracks from propagating if a crack is generated in the composite material. The cell/battery provides immiscible characteristics of silicon and tin and phase separation to minimize electrochemical sintering so as to prevent coalescence of the particles that lead to rapid mechanical degradation of the electrode material. The cell/battery performs phase separation occurring with amorphous phase clusters of silicon being embedded in a generally continuous phase of crystalline or amorphous tin, so that resulting negative electrode materials exhibit significant improvements in charge storage capability along with excellent cycling stability.    DESCRIPTION OF DRAWING(S) - The drawing shows a photograph of a scanning electron microscope image illustrating surface morphologies of phase separated Silicon40Tin60 compositions formed by sputtering of tin and silicon from separate targets onto a copper strip substrate.