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.