Elucidating and Minimizing the Space-Charge Layer Effect between NCM Cathode and Li₆PS₅Cl for Sulfide-Based Solid-State Lithium Batteries

The electrochemical performance of all-solid-state lithium batteries (ASSLBs) can be significantly improved by addressing the challenges posed by space charge layer (SCL) effect, which plays a crucial role in determining Li⁺ ions transport kinetic at cathodic interface. Therefore, it is critical to realize the in situ inspection and visualization of SCL behaviors for solving sluggish Li⁺ ions transport issues, despite remaining grant challenges. Therewith, the well-defined model of LiNbO₃-coated NCM (NCM@LNO) cathode is constructed and assembled for the representative Li₆PS₅Cl-based ASSLBs, which not only ensures excellent cathodic compatibility, but also preferably enables the better monitoring of Li⁺ ions transport kinetics. Combining ex situ analysis with DFT calculation, the formation and evolution mechanism of SCL are comprehensively understood, and the relationship between well-controlled SCL configuration and Li⁺ electrochemical behavior has been also further illustrated and established through the operando Raman spectroscopy. On these grounds, the preferred NCM@LNO cathodes acquire the enhanced discharge capacity of 90.6% (144.8 mAh g⁻¹) after 100 cycles and it can still deliver the exceptional capacity of 136.2 mAh g⁻¹ after 800 cycles in ASSLBs. Hence, the research will pave up a new perspective for fundamental scientific insight of the SCL and reasonable tailoring of cathodic interface for high-efficiency ASSLBs. © 2024 Wiley-VCH GmbH.