Built-in garnet-rich composite solid electrolyte towards fast ion transport and dendrite-free for high-energy lithium batteries

Composite solid-state electrolytes (CSEs), which could provide greater flexibility to harness the advantages of single-phase electrolytes, are promising candidates for solid-state lithium (Li) batteries. However, the agglomeration of inorganic phase obstructs the efficient ion-conduction channel and accelerates dendrite growth, limiting the practical application of CSEs. Herein, a flexible garnet-rich composite skeleton is prepared by incorporating well-dispersed Li6.4La3Zr1.4Ta0.6O12 (LLZTO) with robust polyimide scaffold through a simple method. Subsequently, a compact composite bi-phase electrolyte with abundant and well-dispersed built-in LLZTO could be attained via in-situ curing of a poly(ethylene glycol)diacrylate-based polymer electrolyte within this skeleton. Capitalizing on the rapid Li+ pathways contributed by the high fraction and well-distributed ceramic phase, this electrolyte demonstrates remarkably ionic conductivity and Li+ transference number of 0.95 mS cm−1 and 0.81, respectively. The deigned bi-phase composite enables a stable and uniform Li stripping/plating in symmetrical Li||Li batteries over 1000 h at 0.2 mA cm−2 and a high critical current density of 1.9 mA cm−2, facilitated by enhanced Li+ conduction dynamics and homogenous Li+ flux. LiNi0.8Co0.1Mn0.1O2||Li cells using this electrolyte exhibit favorable battery performances (159.8 mAh g−1, 96.4%@180 cycles, 0.5C). Furthermore, this scalable fabrication process for this composite electrolyte holds great potential in grid-scale production for safe and high-energy Li batteries.