Method of making an anode structure containing a porous region

A method of making a lithium battery anode structure, the method comprising:

• immersing a substrate including at least an upper portion that is composed of p-doped silicon in concentrated hydrogen fluoride while utilizing an anodization setup;
• applying an electrical current to the anodization setup;
• and
• anodizing the substrate electrochemically, wherein the anodizing provides a structure composed entirely of at least one semiconductor material and of unitary construction, wherein the structure includes a non-porous region and a porous region comprising a top porous layer having a first thickness and a first porosity, and a bottom porous layer located beneath the top porous layer and forming an interface with the non-porous region, wherein at least an upper portion of the non-porous region and an entirety of the porous region are composed of silicon, and wherein the bottom porous layer has a second thickness that is greater than the first thickness, and a second porosity that is greater than the first porosity, and wherein the upper porous region represents a topmost portion of the structure.