Stereoelectronic Additive Engineering Enables Solvation Regulation and Dual‐Interphase Stabilization for High‐Voltage and High‐Temperature Lithium Metal Batteries

High‐voltage lithium metal batteries (LMBs) suffer from unstable Li + solvation and fragile electrode/electrolyte interphases, especially at elevated temperatures. Here, difluorotrimethylsilanylacetic acid ethyl ester (DTAE) is introduced as a stereoelectronically engineered additive for conventional carbonate electrolytes to regulate Li + solvation and stabilize both cathode and anode interphases. The push–pull effect of the ─Si(CH 3 ) 3 and ─CF 2 ─ groups on the same carbon center weakens Li + –carbonyl coordination, promotes anion involvement in the primary solvation sheath, and facilitates Li + desolvation. Meanwhile, DTAE scavenges HF and contributes to the formation of robust LiF/Si─O‐rich interphases on both the LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode and Li metal anode. As a result, transition‐metal dissolution, cathode surface degradation, and heterogeneous lithium deposition are effectively suppressed, leading to improved interfacial kinetics and electrochemical stability under harsh conditions. Li||NCM811 cells achieve 82.91% capacity retention after 330 cycles at 4.6 V and 82.32% after 250 cycles at 60°C and 4.5 V. In addition, a 5 Ah pouch cell with an energy density of 415 Wh kg −1 retains 83.40% of its initial capacity after 100 cycles at 4.6 V. This work highlights stereoelectronic additive engineering as an effective strategy to couple solvation regulation with dual‐interphase stabilization for practical high‐energy LMBs.