Enhanced Electrochemical Performance and Safety of Silicon by a Negative Thermal Expansion Material of ZrW2O8.

Silicon (Si) faces big challenges in serious volume changes for applications in spite of its high theoretical capacity. Herein, a novel and facile method was proposed to decrease the volume change by simultaneously in situ absorbing the generated heat of only Si using a negative thermal expansion (NTE) material of ZrW2O8. The Si modified with 2 wt % of ZrW2O8 exhibits excellent structural integrity, electrochemical performance, and safety under various conditions, especially at elevated temperatures. Its reversible capacities can remain 1187.2 mA h g-1 after 50 cycles and 643.8 mA h g-1 after 100 cycles at 2 A g-1 (∼199 and ∼190% higher than that of Si, respectively) at 25 °C. In addition, 930.6 mA h g-1 is maintained after 50 cycles at 60 °C (∼219% higher than that of Si). As current densities increase to 2 and 4 A g-1, the values still remain 1389.4 and 757.5 mA h g-1, respectively, much higher than that of Si. Furthermore, the strain of Si is reduced by 37.2% using ZrW2O8 at 60 °C. Various products were analyzed, and the possible enhanced mechanism was discussed using multiple techniques. These findings exhibit significant potential for the improvement of energy materials using NTE materials by combining thermal effects and volume changes as well as the improved interface behavior.