Composite substrate for rechargeable lithium battery and rechargeable lithium battery including the same

A rechargeable lithium battery, comprising:

• a composite substrate that includes a support layer and a metal layer on the support layer;
• and
• a battery cell on the metal layer,
• wherein the metal layer includes:
• a first region to which a tab is configured to be attached;
• and
• a second region different from the first region,
• wherein a ratio of surface roughness of the first region to surface roughness of the second region is in a range of about 3.5 to about 7.

A rechargeable lithium battery, comprising:

• a composite substrate that includes a support layer and a metal layer on the support layer;
• a first active material layer on the metal layer;
• a separator on the first active material layer;
• a second active material layer on the separator;
• a metal substrate on the second active material layer;
• a first tab attached to the metal layer;
• and
• a second tab attached to the metal substrate,
• wherein the metal layer includes a first recess that is recessed by the first tab,
• wherein the metal substrate includes a second recess that is recessed by the second tab, and
• wherein a depth of the first recess is greater than a depth of the second recess.