Sequencing polymers to enable solid-state lithium batteries.

Rational designs of solid polymer electrolytes with high ion conduction are critical in enabling the creation of advanced lithium batteries. However, known polymer electrolytes have much lower ionic conductivity than liquid/ceramics at room temperature, which limits their practical use in batteries. Here we show that precise positioning of designed repeating units in alternating polymer sequences lays the foundation for homogenized Li+ distribution, non-aggregated Li+-anion solvation and sequence-assisted site-to-site ion migration, facilitating the tuning of Li+ conductivity by up to three orders of magnitude. The assembled all-solid-state batteries facilitate reversible and dendrite-mitigated cycling against Li metal from ambient to elevated temperatures. This work demonstrates a powerful molecular engineering means to access highly ion-conductive solid-state materials for next-generation energy devices.

Controlled Radical Copolymerization toward Tailored F/N Hybrid Polymers by Using Light-Driven Organocatalysis.

Controlled radical copolymerizations present attractive avenues to obtain polymers with complicated compositions and sequences. In this work, we report the development of a visible-light-driven organocatalyzed controlled copolymerization of fluoroalkenes and acyclic N-vinylamides for the first time. The approach enables the on-demand synthesis of a broad scope of amide-functionalized main-chain fluoropolymers via novel fluorinated thiocarbamates, facilitating regulations over chemical compositions and alternating fractions by rationally selecting comonomer pairs and ratios. This method allows temporally controlled chain-growth by external light, and maintains high chain-end fidelity that promotes facile preparation of block sequences. Notably, the obtained F/N hybrid polymers, upon hydrolysis, afford free amino-substituted fluoropolymers versatile for post modifications toward various functionalities (e.g., amide, sulfonamide, carbamide, thiocarbamide). We further demonstrate the in-situ formation of polymer networks with desirable properties as protective layers on lithium metal anodes, presenting a promising avenue for advancing lithium metal batteries.

Reactive Solid Polymer Layer: From a Single Fluoropolymer to Divergent Fluorinated Interface.

Controlling the structure and chemistry of solid electrolyte interphase (SEI) underpins the stability of electrolyte-electrode interface, and is crucial for advancing rechargeable lithium metal batteries (LMBs). Here, we utilized photo-controlled copolymerization to achieve the on-demand synthesis of fluorosulfonyl fluoropolymers as unprecedented artificial SEI layers on Li metal anodes. This work not only enables instant formation of a hybrid polymer-inorganic interphase that consists of a polymer-enriched top layer and a LiF-fortified bottom layer, originating from a single polymeric component, but also imparts various desirable physical properties (e.g., good mechanical strength and flexibility, high ion conductivity, low overpotential) to SEI via a single-to-divergent strategy. Model reactions and structural characterizations supported the formation of a divergent fluorinated interphase, which furnished prolonged stabilization of Li deposition, high coulombic efficiency and improved cycling behavior in electrochemical experiments. This work highlights the great potential of exploring reactive polymers as versatile coatings to stabilize Li metal anodes, providing a promising avenue to solve electrode-electrolyte interfacial problems for LMBs.

Designing F/P Hybrid Polymer as Ultrastable Cationic Shielding Interphase for High-Performance Lithium Metal Batteries.

Dendrite growth on electrode-electrolyte interphase has severely limited applications of lithium metal batteries (LMBs). Here, we developed an ionic alternating polymer with fluorocarbons and phosphonium cations in repeating units to regulate Li deposition for the first time. The combined functionalities in the F/P hybrid polymer exhibit remarkable characteristics as a protective layer on top of Li anode, demonstrating outstanding electrochemical stability, ion flux redistributing capability and adaptive chain mobility. Based on characterizations and simulations, this cationic interlayer could effectively furnish long-standing electrostatic shielding for anodes, allowing restrained coating decomposition and homogenized electric field distribution to induce dendrite-free Li deposition, and enabling full cells with enhanced rate and long-term cycling performance. Given the importance of LMBs, this work will promote polymer design to stabilize anodes with superior electrochemical behavior.

Main-Chain Fluoropolymers with Alternating Sequence Control via Light-Driven Reversible-Deactivation Copolymerization in Batch and Flow.

Polymers with regulated alternating structures are attractive in practical applications, particularly for main-chain fluoropolymers. We for the first time enabled controlled fluoropolymer synthesis with alternating sequence regulation using a novel fluorinated xanthate agent via a light-driven process, which achieved on-demand copolymerization of chlorotrifluoroethylene and vinyl esters/amides under both batch and flow conditions at ambient pressure. This method creates a facile access to fluoropolymers with a broad fraction range of alternating units, low dispersities and high chain-end fidelity. Moreover, a two-step photo-flow platform was established to streamline the in-situ chain-extension toward unprecedented block copolymers continuously from fluoroethylene. Influences of structural control were illustrated with thermal and surface properties. We anticipate that this work will promote advanced material engineering with customized fluoropolymers.

Photoorganocatalyzed Reversible-Deactivation Alternating Copolymerization of Chlorotrifluoroethylene and Vinyl Ethers under Ambient Conditions: Facile Access to Main-Chain Fluorinated Copolymers.

Fluoropolymers have found broad applications for many decades. Considerable efforts have focused on expanding access toward main-chain fluorinated polymers. In contrast to previous polymerizations of gaseous fluoroethylenes conducted at elevated temperatures and with high-pressure metallic vessels, we here report the development of a photoorganocatalyzed reversible-deactivation radical alternating copolymerization of chlorotrifluoroethylene (CTFE) and vinyl ethers (VEs) at room temperature and ambient pressure by exposing to LED light irradiation. This method enables the synthesis of various fluorinated alternating copolymers with low D and high chain-end fidelity, allowing an iterative switch of the copolymerization between "ON" and "OFF" states, the preparation of fluorinated block alternating copolymers, as well as postsynthetic modifications.

Precise Synthesis of Ultra-High-Molecular-Weight Fluoropolymers Enabled by Chain-Transfer-Agent Differentiation under Visible-Light Irradiation.

Ultra-high-molecular-weight (UHMW) polymers display outstanding properties and hold potential for wide applications. However, their precise synthesis remains challenging. Herein, we developed a novel reversible-deactivation radical polymerization based on the strong and selective fluorine-fluorine interaction, allowing chain-transfer agents to spontaneously differentiate into two groups that take charge of the chain growth and reversible deactivation of the growing chains, respectively. This method enables dramatically improved livingness of propagation, providing UHMW polymers with a surprisingly narrow molecular weight distribution (D≈1.1) from a variety of fluorinated (meth)acrylates and acrylamide at quantitative conversions under visible-light irradiation. In situ chain-end extensions from UHMW polymers facilitated the synthesis of well-defined block copolymers, revealing the excellent chain-end fidelity achieved by this method.

Light-intensity switch enabled nonsynchronous growth of fluorinated raspberry-like nanoparticles.

Raspberry-like (RB) nanoparticles hold potential for diverse applications due to their hierarchical morphology. Here we developed a novel tandem synthetic approach of nonsynchronous growth based on photo-mediated reversible-deactivation radical polymerization, enabling simple, efficient and bottom-up synthesis of RB nanoparticles of uniform sizes at quantitative conversions of fluorinated monomers. Chain transfer agents of different chain lengths, concentrations and chemical compositions were varied to tune the diameter of RB particles. Importantly, fluorinated RB nanoparticles obtained with this method allow facile post modifications via both covalent bond formation and intermolecular physical interactions without disrupting the RB morphology. The facile nature of this method and versatility of the obtained fluorinated RB materials open new opportunities for the development of functional materials using nanoparticles.

Fluorous-Core Nanoparticle-Embedded Hydrogel Synthesized via Tandem Photo-Controlled Radical Polymerization: Facilitating the Separation of Perfluorinated Alkyl Substances from Water.

Per- and polyfluorinated alkyl substances (PFASs) are broadly used as surfactants and water/oil repellents for many decades. However, they are toxic, environmental persistence, and widely detected in water sources. In this work, we developed a fluorous-core nanoparticle-embedded hydrogel (FCH) synthesized by the metal-free tandem photocontrolled radical polymerization under visible-light irradiation. With the FCH material, the scope of absorbable PFASs has been expanded to neutral, anionic, cationic and zwitterionic PFASs with the same adsorbent for the first time. The fluorous nanoparticles exhibited strong and selective affinity toward PFASs without being dramatically influenced by pH levels and background ions, enabling efficient removing of PFASs at high to environmentally relevant concentrations (10 mg/L to 1 µg/L). Furthermore, the FCH network has shown good mechanical performance, facilitating the separation, regeneration, and recycling of adsorbent for multiple runs. These results demonstrate the promise of the FCH material for PFASs separation and adsorbent recycling toward sustainable environment.