Decreased Deformation and Heat as well as Improved Interface and Diffusion of Silicon To Enhance Electrochemical Performance and Safety by a Negative Thermal Expansion Material

Abstract

Severe deformation, thermal runaway, and low ionic migration do harm to the applications of silicon. Herein, a negative thermal expansion material of LiTi2(PO4)3 (LTP) with high ionic conductivity was synthesized and utilized to modify nanoscaled Si, and its effects were investigated. Si modified with 3 wt % LTP (SL3) shows the best performance, and its discharge capacities retain 849.4 and 410.9 mAh/g after 100 cycles at 2 A/g as temperatures are 25 and 60 °C, respectively, about 245.4 and 399.9% higher than those of Si. At 60 °C, the diffusion coefficient of lithium ions in Si is increased by 26 times, while the voltage difference between the main redox peaks, charge transfer resistance, and strain of the SL3 are 0.43 V, 171.4 Ω/cm2, and 211 με, respectively, around 15.7, 94.8, and 45.3 lower than those of the Si. The released heat of SL3 is declined to 175.4 J/g, about 85.9% that of the Si. The improvement mechanism of Si by LTP is discussed. It provides a path for enhancing the performance and safety of materials by decreasing heat and deformation hazards, improving the interface, and intensifying transfer.