Directional Polarization of a Ferroelectric Intermediate Layer Inspires a Built-In Field in Si Anodes to Regulate Li Transport Behaviors in Particles and Electrolyte.

The silicon (Si) anode is prone to forming a high electric field gradient and concentration gradient on the electrode surface under high-rate conditions, which may destroy the surface structure and decrease cycling stability. In this study, a ferroelectric (BaTiO) interlayer and field polarization treatment are introduced to set up a built-in field, which optimizes the transport mechanisms of Li in solid and liquid phases and thus enhances the rate performance and cycling stability of Si anodes. Also, a fast discharging and slow charging phenomenon is observed in a half-cell with a high reversible capacity of 1500.8 mAh g when controlling the polarization direction of the interlayer, which means a fast charging and slow discharging property in a full battery and thus is valuable for potential applications in commercial batteries. Simulation results demonstrated that the built-in field plays a key role in regulating the Li concentration distribution in the electrolyte and the Li diffusion behavior inside particles, leading to more uniform Li diffusion from local high-concentration sites to surrounding regions. The assembled lithium-ion battery with a BaTiO interlayer exhibited superior electrochemical performance and long-term cycling life (915.6 mAh g after 300 cycles at a high current density of 4.2 A g). The significance of this research lies in exploring a new approach to improve the performance of lithium-ion batteries and providing new ideas and pathways for addressing the challenges faced by Si-based anodes.