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[Display omitted] The active cyano-group in polyacrylonitrile has severe passivation of lithium anode under larger current density, which restricts the wide application of polyacrylonitrile(PAN) in lithium metal batteries. Herein, in order to address the excessive passivation of lithium metal by PAN, inspired by the pre-oxidation of carbon fibers, PAN was pre-oxidized at 230 °C, which transformed part of the cyano group into a more chemically stable cyclized structure. The electrochemical and mechanical properties of the composite solid electrolyte were effectively improved by introducing the fast ionic conductor Li 6.25 La 3 Zr 2 Al 0.25 O 12 into PAN by electrospinning. The oxidized PAN-based composite solid electrolyte presents high ionic conductivity (3.05 × 10−3 S·cm−1) and high lithium transference number of 0.79 at 25 °C, further contributing to a high electrochemical window (5.3 V). The solid-state batteries assembled by Li||10 wt%-LLZAO@230-oxy-PAN||NCM523 behave superb electrochemical performance, delivering a high initial discharge capacity of 157 mAh g−1 at 0.2 C. After 100 cycles, the capacity retention was 93.3 %, indicating the electrolyte displays great electrochemical stability. This work provides new insights into the structural design of polymer-based high-voltage batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] The garnet ceramic Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) modified separators have been proposed to overcome the poor thermal stability and wettability of commercial polyolefin separators. However, the side reaction of LLZTO in the air leads to deterioration of environmental stability of composite separators (PP-LLZTO), which will limit the electrochemical performance of batteries. Herein, the LLZTO with the polydopamine (PDA) coating (LLZTO@PDA) was prepared by solution oxidation, and then applied it to a commercial polyolefin separator to achieve a composite separator (PP-LLZTO@PDA). LLZTO@PDA is stable in the air, and no Li 2 CO 3 can be observed on the surface even after 90 days in the air. Besides, LLZTO@PDA coating endows the PP-LLZTO@PDA separator with the tensile strength (up to 103 MPa), good wettability (contact angle 0°) and high ionic conductivity (0.93 mS cm−1). Consequently, the Li/PP-LLZTO@PDA/Li symmetric cell cycles stably for 600 h without significant dendrites generation, and the assembled Li//LFP cells with PP-LLZTO@PDA-D30 separators deliver a high capacity retention of 91.8% after 200 cycles at 0.1C. This research provides a practical strategy for constructing composite separators with excellent environmental stability and high electrochemical properties. [ABSTRACT FROM AUTHOR]