High Solid and Conductivity Solid Electrolyte Interface Regulated by Novel SilaBLne Additive for High-Performance Si/C Anode at -20 °C

Abstract

With high lithium storage performance and low intercalation/deintercalation potentials, silicon-based anode is one of the most promising anode materials for the development of high-energy density lithium-ion batteries (LIBs). Despite the considerable advances made by Si/C negative electrodes in the commercial field, there remains scope for enhancement in terms of their low-temperature performance. In this work, we put forward a novel additive, which is tetrakis(trimethylsilyl)silane (TTS). Theoretical calculations and differential capacity curves demonstrated that the additive is able to preferentially carbonate solvents for decomposition and that the chemical bonds formed by the breakage facilitated the formation of surface films. The incorporation of O-Si-C-rich structures into solid electrolyte interface (SEI) film allows for the attainment of better mechanical properties and high ionic conductivity. The particular SEI is capable of tolerating significant alterations in the volume of Si/C anode particles, thereby preventing the irreversible depletion of lithium ions and electrolytes. Thus, the Si/C half-cell with TTS additive exhibits higher reversible capacity (582.1 mAh g^-1 at room temperature, 212.3 mAh g^-1 at -20°C), high-rate performance (440.3 mAh g^-1 at 2 C), and excellent capacity retention (76.2% after 150 cycles at room temperature, 77.9% after 200 cycles at -20°C). Furthermore, our research explores the impact of TTS on the formation of amorphous silicon. On the one hand, the formed SEI containing O-Si-C structure has better mechanical properties and ionic conductivity, which inhibit the fragmentation of Si/C particles and reduce the irreversible consumption of Li⁺. On the other hand, an increase in Li⁺ concentration can increase the amorphous silicon content in the lithiation process. Specifically, the introduction of TTS promotes the formation of the amorphous silicon (a-Si) phase, and the content of the a-Si phase is closely related to the reversible capacity and cycling stability of the silicon anode. The unique phase-regulation mechanism is the key to the ability of TTS modification to enhance the low-temperature electrochemical performance of Si/C anode. This work provides an effective method for the development of materials suitable for operation at low-temperature.