Decreasing Deformation and Heat as Well as Intensifying Ionic Transport of Si Using a Negative Thermal Expansion Ceramic with High Ionic Conductivity

Abstract

Silicon is an attractive anode material with high capacity, but its application is hampered by some problems such as severe volume change, low ionic migration ability, thermal runaway, and capacity fade. Herein, a facile way was proposed to alleviate deformation and improve ionic transport and thermal stability of nanoscaled Si by in situ absorbing heat using a negative thermal expansion ceramic of LiAlSiO4 with high ionic conductivity. The Si modified with 3 wt % LiAlSiO4 (SL3) exhibits the best electrochemical performance, and the specific discharge capacities can retain 777.4 and 464.3 mAh g–1 after 100 cycles at 25 and 60 °C at 2 A g–1, respectively, about 239.6 and 256.6% higher than those of Si. The value can reach 807.8 mAh g–1 at 4 A g–1, about 79.0% higher than that of Si. Compared to those of the Si, the strain, R ct, and heat from DSC of SL3 are reduced by approximately 67.5, 34.0, and 65.6%, respectively, while the lithium-ion diffusion coefficient is increased by ∼192.4%. According to the abundant results at different states, enhancement mechanisms were discussed. This strategy offers a novel perspective for improving the electrochemical performance and safety of energy materials via adjusting heat, deformation, ionic diffusion, and interface.