Safe and Energy-Dense Flexible Solid-State Lithium–Oxygen Battery with a Structured Three-Dimensional Polymer Electrolyte

Solid-state lithium–oxygen batteries (SSLOBs) with high energy density and enhanced safety are promising for green energy storage but plagued by limited O2/Li+/e– triple-phase reaction zone and high internal resistance. Herein, we design and fabricate a novel SSLOB with an integrated cathode and electrolyte structure in which carbon nanotubes were uniformly coated by an in situ-formed hybrid polymer electrolyte (HPE). This interface engineering builds a three-dimensional hybrid electronic and ionic conductor with sufficient void spaces, which facilitates oxygen diffusion and product accommodation and contributes to a significant expansion of the triple-phase reaction zone. The HPE is prepared in situ from poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), trimethyl phosphate (TMP), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) via weak hydrogen bond interactions and shows a flame-resistant property and high electrochemical stability (until 5.4 V). More importantly, it exhibits both a high ionic conductivity (1.08 × 10–3 S cm–1) and high lithium ion transference number (tLi+ up to 0.73) at ambient temperature, promoting uniform Li deposition. In consequence, the battery displays a gravimetric energy density of 542.1 Wh kg–1 (calculated from the weight of the whole device), superior rate performance, and long cycle life (1000 cycles, 167 days). These systems may promote the practical application of SSLOBs in next-generation energy storage.