Highly Ionic Conductive, Self-Healing, Li10GeP2S12-Filled Composite Solid Electrolytes Based on Reversibly Interlocked Macromolecule Networks for Lithium Metal Batteries with Improved Cycling Stability.

Ceramic-polymer composite solid electrolytes (CSEs) have attracted great attention by combining the advantages of polymer electrolytes and inorganic ceramic electrolytes. Herein, Li10GeP2S12 (LGPS) particles are incorporated into poly(ethylene oxide) (PEO)-based reversibly interlocked polymer networks (RILNs) derived from the topological rearrangement of two PEO networks cross-linked by reversible imine bonds and disulfide linkages. A series of highly ionic conductive, self-healing CSEs are obtained accordingly. The interlocking architecture successfully inhibits PEO crystallization, increasing the amorphous phase for Li ion transportation, and stabilizes the conductive pathways of LGPS particles by its unique confinement effect. Meanwhile, the LGPS particles cooperate with the RILN matrix, forming a filler-polymer interfacial phase for additional Li ion transportation and strengthening and toughening the resultant CSEs via the strong intermolecular Li+-O2- interactions. Furthermore, the dynamic characteristics of the included reversible bonds ensure a multiple intrinsic self-healing capability. Consequently, the CSEs containing 15 wt % LGPS deliver a high ionic conductivity (1.06 × 10-3 S cm-1) and high Li ion transference number (∼0.6) at 25 °C, a wide electrochemical stability window (>4.9 V), good mechanical properties (0.63 MPa, 377%), and a stable CSE/Li anode interface. The integrated Li/CSE/LiFePO4 battery exhibits a specific discharge capacity of 110.8 mAh g-1 at 1 C (25 °C) and a capacity retention of 76.9% after 200 cycles. Thanks to the healability, the damaged CSEs can regain the structural integrity, ion conductive capability, and cycling performance of the assembled cells. The present work provides an effective strategy to fabricate CSEs for lithium metal batteries that are workable at ambient temperature.

Highly flexible yet strain-insensitive conjugated polymer.

Imparting excellent electrical properties, mechanical robustness, suppleness, conduction stability during deformation, and self-healing to intrinsic conducting polymers is a challenging endeavor. The reversibly interlocked macromolecular networks (RILNs) approach is utilized to tackle this problem. Specifically, poly(3,4-ethylenedioxythiophene) (PEDOT) is mixed with flexible polysulfonic acid networks crosslinked by reversible Diels-Alder bonds, while rigid polyaniline networks crosslinked by reversible Schiff base bonds act as molecular staples. Owing to the joint actions of the doping effect of polyaniline on PEDOT, the specific interlocking architecture and synergy between the component materials, the electrical conductivity (59.3-980.5 S cm-1), tensile strength (8.4-81.6 MPa) and elongation at break (44.5-411.0%) of the resultant PEDOT/RILNs films is significantly tunable according to different usage scenarios by adjusting the PEDOT content from 1.48 to 22.24 wt%. More importantly, the electrical resistance of PEDOT/RILNs remains constant during not only a single large extension and deflection but also repeated stretching (up to 1500 cycles) and bending (up to 106 cycles). The built-in reversible covalent bonds enable the PEDOT/RILNs to autonomously restore damaged mechanical and electrical performance. These record-breaking results and the demonstration of self-powered sensor made of PEDOT/RILNs suggest that the proposed approach successfully satisfies various conflicting requirements of flexible electronics regarding the properties of conducting polymers.

Sunlight Stimulated Photochemical Self-Healing Polymers Capable of Re-Bonding Damages up to a Centimeter Below the Surface Even Out of the Reach of the Illumination.

The development of photochemical self-healing polymers faces the the following bottlenecks: i) only the surface cracks can be restored and ii) materials' mechanical properties are lower. To break these bottlenecks, cross-linked poly(urethane-dithiocarbamate)s carrying photo-reversible dithiocarbamate bonds covalently linked to indole chromophores and benzyl groups are designed. The conjugated structure of the chromophore and benzyl enhances the addition reactivity of thiocarbonyl moiety and facilitates photo-cleavage of CS bond, so that transfer of the created radicals among dithiocarbamate linkages is promoted. Accordingly, reshuffling of the reversibly cross-linked networks via dynamic exchange between the activated dithiocarbamates is enabled in both surface layer and the interior upon exposure to the low-intensity ultraviolet (UV) light from the sun. It is found that the damages up to a centimeter below the surface can be effectively recovered in the sunshine, which greatly exceeds the maximum penetration distance of UV light (hundreds of microns). Besides, tensile strength and failure strain of the poly(urethane-dithiocarbamate) are superior to the reported photo-reversible polymers, achieving the record-high 33.8 MPa and 782.0% owing to the wide selectivity of soft/hard blocks, multiple interactions, and appropriate cross-linking architecture. The present work provides a novel paradigm of photo self-healing polymers capable of re-bonding cracks even out of the reach of the illumination.

Tailored modular assembly derived self-healing polythioureas with largely tunable properties covering plastics, elastomers and fibers.

To impart self-healing polymers largely adjustable dynamicity and mechanical performance, here we develop libraries of catalyst-free reversible polythioureas directly from commodity 1,4-phenylene diisothiocyanate and amines via facile click chemistry based modular assembly. By using the amine modules with various steric hindrances and flexibilities, the reversible thiourea units acquire triggering temperatures from room temperature to 120 °C. Accordingly, the derived self-healable, recyclable and controlled degradable dynamically crosslinked polythioureas can take effect within wide temperature range. Moreover, mechanical properties of the materials can be tuned covering plastics, elastomers and fibers using (i) different assemble modules or (ii) solid-state stretching. Particularly, unidirectional stretching leads to the record-high tensile strength of 266 MPa, while bidirectional stretching provides the materials with biaxial strengths up to over 120 MPa. The molecular mechanism and technological innovations discussed in this work may benefit promotion and application of self-healing polymers towards greatly diverse demands and scenarios.

Performance improvement of N-doped carbon ORR catalyst via large through-hole structure.

N-doped carbon-based materials are crucial electrically conductive additives and non-metal electrocatalysts for the oxygen reduction reaction. At present, many pieces of research are focused on the effects of micropore, mesopore and hierarchical pore structure on the catalytic activity, however, there are few works concerning the role of large-dimension through-hole structure. Hence, in this work, we prepare two kinds of carbon materials with large through-hole structure, i.e. N-doped carbon hollow-spheres and hollow-tubes, as the oxygen reduction catalysts. The synthesis follows template-free morphology-controlled pyrolysis, which is more convenient than the preparation of conventional N-doped nanotubes and graphene. The resultant N-doped carbon hollow-spheres and hollow-tubes evidently enhanced their ORR catalytic activity, remarkable long-term stability and methanol resistance. The large-dimension through-hole structure is found to account for the increase in mass transfer.

Reversibly Interlocked Macromolecule Networks with Enhanced Mechanical Properties and Wide pH Range of Underwater Self-Healability.

A novel strategy for developing homogeneous reversibly interlocking polymer networks (RILNs) with enhanced mechanical properties and underwater self-healing ability is proposed. The RILNs are prepared by the topological reorganization of two preformed cross-linked polymers containing reversible catechol-Fe3+ coordinate bonds and imine bonds and exhibit enhanced mechanical properties, superior underwater self-healing effect within a wide pH range, and water-assisted recycling ability through synergetic action between the reversible catechol-Fe3+ and imine bonds. At higher pH values, the catechol-Fe3+ coordinate bonds are responsible for self-healing, while the imine bonds maintain the stability of the materials. In neutral water, the imine bonds mainly account for self-healing, and hydrogen bonds and entanglements between the two networks prevent the material from collapsing. Under a lower pH value, intermolecular hydrogen bonds and entanglements contribute to self-healing. The outcomes of this work provide a new idea for developing robust multifunctional underwater self-healing materials.