Porous hybrid encapsulation enables high-rate lithium storage for a micron-sized SiO anode.

Abstract

Establishing a durable interfacial layer between an electrode and electrolyte to enable micron-sized silicon-based lithium-ion battery (LIB) anodes to achieve superior electrochemical performance is highly desired. Recent studies have shown that heterogeneous encapsulation with enhanced ion/electron transport is an effective strategy. However, the structural design of the existing hetero-coated interface lacks a reasonable ion/electron transport channel, resulting in high interfacial impedance. Herein, we designed a heterogenous MXene-mesoporous polypyrrole (mPPy) encapsulation layer onto micron-sized SiO particles. The MXene coating layer functions as a bridging interface that can build a strong chemical link to internal SiO via covalent bonding, thus reinforcing interfacial charge transfer rate. Meanwhile, it forms a dynamic connection with the outer mPPy through hydrogen bonding, which contributes to high interfacial Li+ concentration and ion/electron coupling transport rate. Accordingly, the as-prepared SiO@MXene@mPPy anode delivers a boosted specific capacity of 673.9 mA h g-1 at 2 A g-1 after 1000 cycles and high-rate capability of 777.4 mA h g-1 at 5 A g-1. Further, electrochemical kinetic analysis indicates that the MXene@mPPy coating layer shows a pseudocapacitance controlled Li storage mechanism, thereby displaying improved high-rate capability. This porous hybrid encapsulation strategy offers new possibilities for a micron-sized SiO anode to achieve an excellent performance.