Porous silicon negative electrodes for rechargeable lithium batteries

Porous silicon (PS) negative electrodes with one-dimensional (1-D) channels have been successfully fabricated using an electrochemical etching process. The peak current and the amount of charge transferred during cyclic voltametry (CV) increase with the channel depth of the PS, indicating that the channel wall of the PS participates in the lithiation/delithiation process. The channel structure of the PS electrodes remains essentially the same after 35 CV cycles in spite of the severe deformation of the channel wall during the repetitive lithium alloying/dealloying process. The specific capacity of the PS depends critically on the degree of activation of the PS before the galvanostatic charge/discharge experiment. For an exemplary PS electrode pre-activated by 20 CV cycles, the reversible specific capacity of the PS reached 43 μA h cm−2. After a subsequent activation by 10 CV cycles, the capacity increased by 40% (60 μA h cm−2). One-dimensional porous silicon appears to be a promising negative electrode for rechargeable micro-batteries.