Heterogeneous PEO/Electrodes Interface Coordination Chemistry Enables High‐Voltage Solid‐State Lithium Metal Batteries via an Asymmetric Electrolyte Design

ABSTRACT The homogenous interface coordination chemistry at both lithium anode and high‐voltage cathode interfaces significantly limits the interfacial optimization efficiency and synergetic stabilization in high‐voltage solid‐state lithium metal batteries (SSLMBs) with poly(ethylene oxide) (PEO)‐based electrolytes. Herein, a heterogenous interface coordination chemistry between Li|PEO and PEO|LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is tailored by asymmetric electrolyte design and interfacial coordination regulators to promote interfacial synergetic stabilization. At Li interface, the Lewis acid Bi site in tris(4‐trifluoromethylphenyl) bismuth dichloride (TBiCl) mitigates strong Li + −EO coordination and catalyzes bis(trifluoromethanesulfonyl)imide (TFSI − ) decomposition via intense TBi 2+ −LiTFSI interaction. This process boosts an in situ generation of dynamic stable mixed conducting interphase rich in LiF and Bi/Li 3 Bi and a favorable lithium plating/stripping cycle over 3000 h. Differently, at NCM811 interface, the strong PEO−lithium difluoro(oxalato)borate (LiDFOB) coordination and preferential passivation effect of LiDFOB facilitate the formation of LiF and B−O‐rich cathode electrolyte interphase, which suppresses continuous electrolyte oxidation and ensures rapid interfacial kinetics. Consequently, the 4.5 V Li/NCM811 cells with asymmetric electrolyte can achieve a high initial capacity of 214.1 mAh g −1 and steadily cycle over 100 cycles. Moreover, the 50 µm Li/NCM811 pouch cell delivers a capacity of 33.5 mAh and demonstrates stable operation under abuse conditions, highlighting the practicality of this asymmetric electrolyte.