Activating interfacial Li+ transportation channels via lithium-rich space charge layers towards stable solid-state lithium-metal batteries

Abstract

The unsatisfactory performance of individual inorganic and organic solid-state electrolytes has driven the development of composite solid electrolytes (CSEs) for solid-state lithium batteries (SSLBs). However, limited Li⁺ transport across lithium-poor space charge layers (SCLs) at the filler/polymer matrix and cathode/CSE interfaces hinders ionic conductivity and compromises the electrochemical performance of SSLBs. Herein, we report a Bi₂O₃-induced lithium-rich SCL that activates interfacial Li⁺ transportation channels between Li_0.35La_0.55TiO₃ (LLTO) filler and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix, enabling efficient Li⁺ diffusion across their interface. This design achieves a remarkable ionic conductivity of 1.63 mS cm⁻¹ and a high lithium transference number of 0.80-approximately two- and three-fold improvements compared to its Bi₂O₃-free counterpart. Additionally, the dielectric properties of Bi₂O₃ generate a built-in electric field, mitigating lithium-poor SCLs and facilitating Li⁺ transport at the cathode/CSE interface. As a result, the Li symmetric cells exhibit stable operation over 1000 h at 0.5 mA cm⁻², while the full SSLBs using LiNi_0.9Co_0.05Mn_0.05O₂ cathode deliver exceptional electrochemical performance, retaining 86.1% capacity after 200 cycles at 0.5 C. The innovation of creating Li-rich SCLs to activate the interfacial Li⁺ transportation channels at the interface provides a new avenue to achieve better CSEs and SSLBs.