Constructing Nano‐Interlayer Inhibiting Interfacial Degradation toward High‐Voltage PEO‐Based All‐Solid‐State Lithium Batteries

Abstract The interfacial instability between PEO‐based solid electrolyte (SPE) and high‐voltage cathode materials inhibits the longevity of high‐energy‐density all‐solid‐state polymer lithium metal batteries (ASSPLBs). Herein, for the first time it is demonstrated, that contact loss caused by gas generation from interfacial side reactions between the high‐voltage cathode and solid polymer electrolyte (SPE) can also arise in ASSPLBs. To alleviate the interfacial side reactions, a LiNb_0.6Ti_0.5O₃ (LNTO) layer is well coated on LiNi_0.83Co_0.07Mn_0.1O₂ (NCM83), denoted as (CNCM83). The LNTO layer with low electronic conductivity reduces the decomposition drive force of SPE. Furthermore, Ti and Nb in the LNTO layer spontaneously migrate inside the NCM83 surface to form a strong Ti/Nb─O bond, stalling oxygen evolution in high‐voltage cathodes. The interfacial degradation phenomena, including SPE decomposition, detrimental phase transition and intragranular cracks of NCM83, and void formation between cathode and SPE, are effectively mitigated by the LNTO layer. Therefore, the growth rate of interfacial resistance (R_CEI) decreases from 37.6 Ω h^−0.5 for bare NCM83 to 2.4 Ω h^−0.5 for CNCM83 at 4.2 V. Moreover, 4.2 V PEO‐based ASSPLBs achieve impressive cyclability with high capacity retention of 135 mAh g⁻¹ (75%) even after 300 cycles at 0.5 C.