Friction-induced lubricating nanocoatings of main-chain thermotropic liquid crystalline polymer

Quasi-Ionic Liquid Enabling Single-Phase Poly(vinylidene fluoride)-Based Polymer Electrolytes for Solid-State LiNi0.6 Co0.2 Mn0.2 O2 ||Li Batteries with Rigid-Flexible Coupling Interphase

Poly(vinylidene fluoride)-based polymer electrolytes are being intensely investigated for solid-state lithium metal batteries. However, phase separation and porous structures are still pronounced issues in traditional preparing procedure. Herein, a bottom-to-up strategy is employed to design single-phase and densified polymer electrolytes via incorporating quasi-ionic liquid with poly(vinylidene fluoride-co-hexafluoropropylene). Due to strong ion/dipole-dipole interaction, the optimized polymer electrolyte delivers high room-temperature ionic conductivity of 1.55 × 10^-3 S cm^-1 , superior thermal and oxidation stability of 4.97 V, excellent stretchability of over 1500% and toughness of 43 MJ cm^-3 as well as desirable self-extinguishing ability. Furthermore, the superb compatibility toward Li anode enables over 3000 h cycling of Li plating/stripping and ≈98% Coulombic efficiency in Li||Cu test at 0.1 mA cm^-2 . In particular, lithium metal battery Li||LiNi_0.6 Co_0.2 Mn_0.2 O₂ exhibits a room-temperature discharge retention rate of 96% after 500 cycles under a rate of 0.1 C, which is associated with the rigid-flexible coupling electrodes/electrolytes interphase. This investigation demonstrates the potential application of quasi-ionic liquid/polymer electrolytes in safe lithium metal batteries.

Ultra-Wear-Resistant MXene-Based Composite Coating via in Situ Formed Nanostructured Tribofilm

Newly emerging two-dimensional (2D) materials of MXenes possess lots of merits, which provide potential solutions for the lubrication issues in harsh conditions. Here, preliminary efforts were devoted to developing an MXene-based 2D composite coating and its antiwear interfacial performance in ambient environments. Macroscale and atomic-scale characterizations were utilized to explore the lubrication behaviors of the composite coating to clarify the influence of the coating composition and tribo-test parameters in the establishment of ultra-wear-resistant sliding interfaces. The results highlighted a unique lubrication mechanism for the 2D MXene composite coating. They suggested that the MXene/nanodiamond coating exhibited almost no wear when rubbed against a polytetrafluoroethylene (PTFE) ball. A nanostructured tribofilm with unprecedented bonding features was in situ formed along the sliding interface. The ultra-wear resistance highly depended on the combined effects of shielding and self-lubrication of PTFE, layer shearing of MXenes, and self-rolling of nanodiamond. These discoveries clearly enrich the 2D material-based lubrication theories and offer technical guidance for designing and exploiting high-performance ultra-wear-resistant materials.