NOVELTY - A lithium-ion or lithium-sulfur secondary electrochemical cell or battery comprises a negative electrode (14) composition utilizing lithium, where the lithium is inserted into a negative electrode composition during charging of the cell or battery and lithium is extracted from the negative electrode composition during discharge of the cell or battery, where the negative electrode material comprises a composite of silicon, tin, and a second metal element selected from aluminum, copper, and titanium. In the composite, silicon, tin, and second metal are present separately in separate phases.    USE - As lithium-ion or lithium-sulfur secondary electrochemical cell or battery (claimed) used as electric storage systems for powering electric and hybrid electric vehicles.    ADVANTAGE - The negative electrode composition exhibits increased lithium insertion capacity and durability. The distinct tin and aluminum phases provide electron conductivity. Each phase accommodates the insertion and extraction of lithium in the operation of the cell and all phases interact in minimizing mechanical damage to the material as the cell experiences repeated charge and discharge cycles. The combination of suitable atomic proportions of silicon, tin, and at least one other metal element, and the sizes of the respective phases in such composites enables the insertion of increased amounts of lithium over repeated electrochemical cycles with less damage to the particulate negative electrode material. The battery or cell exhibits improved volumetric and/or gravimetric capacity.    DETAILED DESCRIPTION - A lithium-ion or lithium-sulfur secondary electrochemical cell or battery comprises a negative electrode (14) composition utilizing lithium, where the lithium is inserted into a negative electrode composition during charging of the cell or battery and lithium is extracted from the negative electrode composition during discharge of the cell or battery, where the negative electrode material comprises a composite of silicon, tin, and a second metal element selected from aluminum, copper, and titanium. In the composite, the silicon, tin, and second metal are present separately in separate phases. The tin phase and the second metal element phase are crystalline or amorphous and the silicon phase is amorphous.    DESCRIPTION OF DRAWING(S) - The figure shows enlarged and exploded cross-sectional view of electrochemical cells.    Thin rectangular-shaped electrochemical battery cells (12)    Negative electrode (14)    Positive electrode (16)    Separator (18)    Negative-electrode metallic current collector (20)    Negative polarity tab (22)    Positive-side metallic current collector (24)    Positive polarity tab (26)    Inner face surface of negative electrode (32)    Outer face surface of negative electrode (34)    Inner face surface of positive electrode (36)    Outer face surface of positive electrode (38)    Negative-side major face surface (40)    Positive-side major face surface (42)