Anions‐Trappable Hollow Mesoporous Nanoparticle Coating Enables High‐Performance and Safe Lithium Metal Batteries

Abstract Polyolefin separators, such as polypropylene (PP) and polyethylene (PE) separators, are the commonly used separators for lithium batteries, which have good mechanical properties and chemical/electrochemical stability, but their high‐temperature dimensional stability is poor and Li⁺ transference number (t _Li⁺) is low. Recently, much attention has been paid to developing separators with new substrates, but so far there is no separator to replace the polyolefin separator for large‐scale application. Therefore, the surface modification of the polyolefin separator to enhance its functionality is a simple and effective method. Among many modified layers, the porous modified layer can store the electrolyte and provide enough space for ion transport. In this work, a hollow mesoporous silica nanosphere (mSiO₂) is prepared for the PP separator multifunctional coating to improve the electrochemical performance and high‐temperature safety of the PP separator. The experimental and theoretical results show that the mSiO₂ coating can not only improve the electrolyte wettability and high‐temperature dimensional stability of the PP separator, but also promote the Li⁺ transport, so that the mSiO₂/PP separator exhibits high ionic conductivity (2.35 mS cm⁻¹) and high t _Li⁺ (0.63). As a result, Li//LiFePO₄ cells using mSiO₂/PP separators exhibit excellent cycling performance, rate performance, and high‐temperature safety.