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

Abstract 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.