Manipulating charge-transfer kinetics and a flow-domain LiF-rich interphase to enable high-performance microsized silicon–silver–carbon composite anodes for solid-state batteries

Abstract

A silicon (Si) anode with a high theoretical specific capacity (3579 mA h g⁻¹) offers great promise for realizing high-energy solid-state batteries (SSBs). However, given Si's huge volume variations during cycling, sluggish kinetics and unfavorable interface stability with a solid-state electrolyte (SSE), its practical potential in SSBs has not been fully exploited. Herein, we propose a design of highly dense Ag nanoparticles decorated with porous microsized Si, which is coated by thin-layer carbon (PS–Ag–C) working as a high-performance anode for boosting SSB performance. Specifically, the mechanical stress at the interface, originating from a large volume change of Si, can be alleviated by the highly porous architecture. Meanwhile, continuous charge transfer within Si can be achieved by the introduction of Ag nanoparticles, a thin carbon layer and the as-formed Ag–Li alloys, which contribute to high-rate capability and stable cycling performance. Furthermore, coupled with a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) SSE with low mobility, a flow-domain LiF-rich solid–electrolyte-interphase (SEI) is formed, ensuring desirable interfacial and mechanical stability. Accordingly, the as-fabricated PS–Ag–C anode achieves high reversible capacities of 3030.3 mA h g⁻¹ at 0.2 A g⁻¹ with an initial Coulombic efficiency of 90% and 1600 mA h g⁻¹ over 500 cycles at 1 A g⁻¹, respectively. In particular, we observed that the highest areal capacity reaches 4.0 mA h cm⁻² over 100 cycles at 0.5 A g⁻¹ in Si-based SSBs with organic–inorganic composite SSEs. Moreover, a solid-state full cell assembled with the as-obtained PS–Ag–C anode and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode demonstrates high capacity and desirable cycling stability. This work provides new insights into developing a high-capacity and durable Si anode for high-performance SSBs.