Self-standing mesoporous Si films as anodes for lithium-ion microbatteries

Silicon is the most promising anode material for next-generation lithium-ion batteries (LIBs) due to its high theoretical specific capacity and safe electrochemical potential. Among the different Si materials, mesoporous Si has attracted attention as the pores can accommodate the volume expansion during cycling, thus leading to stable battery cycling. However, carbon is often added to the electrode to improve the performance of the porous Si electrodes. To investigate the sole effects of the pore characteristics on the battery performance without any contribution from carbon, we produce self-standing mesoporous Si films with different porous structures through electrochemical etching and prepare electrodes without carbon additives or binders. Detailed pore analysis and electrochemical characterization of the Si films are performed to study their correlation. Correlation analysis shows that both reversible specific capacity and initial Coulombic efficiency (ICE) are mainly affected by the porosity and surface area, while the cycling performance is dictated by the film thickness over the pore characteristics. The best Si film anode delivers an ICE of 81.2% and stable cycling for over 450 cycles with a limited specific capacity of 1200 mAh g−1 in half cells. This study indicates the direction of the porous silicon material for high-performance LIBs.