Garnet electrolytes with high ionic conductivity and electrochemical stability are widely used as fillers to fabricate composite solid electrolytes within polymer matrices. However, the performance of composite solid electrolytes (CPEs) is significantly influenced by the surface characteristics of the garnet electrolyte. Herein, the impact of garnet surface characteristics on CPEs was systematically investigated, and a conversion from a typically unstable and Lewis basic surface to a more stable Lewis acidic surface was realized, which is shown to be more conducive to the improved performance of CPEs. By simultaneously removing the Li₂CO₃ layer and applying a Li-Al-O coating, the influence of surface characteristics on CPEs was investigated. The Lewis acid Li-Al-O surface coating not only promotes lithium salt dissociation, improving the ionic conductivity and ionic transfer number, but also prevents the reformation of the passive Lewis basic Li₂CO₃ layer. Compared to garnet with a Lewis basic Li₂CO₃ surface, the garnet modified with a Lewis acid Li-Al-O coating enhances CPEs, which exhibit an improved critical current density of 1.0 mA cm⁻² and highly stable lithium symmetric cell cycling for 400 h at 0.2 mA cm⁻². This research highlights the importance of surface chemistry in the design of high-performance solid-state batteries and presents a strategic modification approach for garnet-based CPEs.

Carbon-based material has been regarded as one of the most promising electrode materials for potassium-ion batteries (PIBs). However, the battery performance based on reported porous carbon electrodes is still unsatisfactory, while the in-depth K-ion storage mechanism remains relatively ambiguous. Herein, we propose a facile "in situ self-template bubbling" method for synthesizing interlayer-tuned hierarchically porous carbon with different metallic ions, which delivers superior K-ion storage performance, especially the high reversible capacity (360.6 mAh·g⁻¹@0.05 A·g⁻¹), excellent rate capability (158.6 mAh·g⁻¹@10.0 A·g⁻¹) and ultralong high-rate cycling stability (82.8% capacity retention after 2, 000 cycles at 5.0 A·g⁻¹). Theoretical simulation reveals the correlations between interlayer distance and K-ion diffusion kinetics. Experimentally, deliberately designed consecutive cyclic voltammetry (CV) measurements, ex situ Raman tests, galvanostatic intermittent titration technique (GITT) method decipher the origin of the excellent rate performance by disentangling the synergistic effect of interlayer and pore-structure engineering. Considering the facile preparation strategy, superior electrochemical performance and insightful mechanism investigations, this work may deepen the fundamental understandings of carbon-based PIBs and related energy storage devices like sodium-ion batteries, aluminum-ion batteries, electrochemical capacitors, and dual-ion batteries.