Highly tough slide-crosslinked gel polymer electrolyte for stable lithium metal batteries.

Gel polymer electrolytes (GPEs) hold great promise for the practical application of lithium metal batteries. However, conventional GPEs hardly resists lithium dendrites growth and maintains long-term cycling stability of the battery due to its poor mechanical performance. Inspired by the slide-ring structure of polyrotaxanes (PRs), herein we developed a dynamic slide-crosslinked gel polymer electrolyte (SCGPE) with extraordinary stretchability of 970.93% and mechanical strength of 1.15 MPa, which is helpful to buffer the volume change of electrodes and maintain mechanical integrity of the battery structure during cycling. Notably, the PRs structures can provide fast ion transport channels to obtain high ionic conductivity of 1.73×10-3 S cm-1 at 30°C. Additionally, the strong polar groups in SCGPE restrict the free movement of anions to achieve high lithium-ion transference number of 0.71, which is favorable to enhance Li+ transport dynamics and induce uniform Li+ deposition. Benefiting from these features, the constructed Li|SCGPE-3|LFP cells exhibit ultra-long and stable cycle life over 1000 cycles and high-capacity retention (89.6% after 1000 cycles). Even at a high rate of 16C, the cells deliver a high capacity of 79.2 mAh g-1. The slide-crosslinking strategy in this work provides a new perspective on the design of advanced GPEs for LMBs.

Biocatalytic Synthesis of Metaxalone and Its Analogues.

A biocatalytic approach for the synthesis of metaxalone and its analogues was developed based on the reaction of epoxides and cyanate catalyzed by halohydrin dehalogenase. Gram-scale synthesis of chiral and racemic metaxalone was achieved with 44% (98% ee) and 81% yields, respectively, by protein engineering of the halohydrin dehalogenase HHDHamb from Acidimicrobiia bacterium. Additionally, various metaxalone analogues were synthesized at 28-40% yields (90-99% ee) for chiral forms and 77-92% yields for racemic forms.

Enantiocomplementary synthesis of ß-adrenergic blocker precursors via biocatalytic nitration of phenyl glycidyl ethers.

Enantiopure ß-nitroalcohols, as an important class of nitro-containing compounds, are essential building blocks in pharmaceutical and organic chemistry, particularly for the synthesis of ß-adrenergic blockers. In this study, we present the successful protein engineering of halohydrin dehalogenase HHDHamb for the enantioselective bio-nitration of various phenyl glycidyl ethers to the corresponding chiral ß-nitroalcohols, using the inexpensive, commercially available, and safer nitrite as a nitrating agent. The chiral (R)- and (S)-1-nitro-3-phenoxypropan-2-ols were synthesized by the several enantiocomplementary HHDHamb variants through the whole-cell biotransformation, which showed good catalytic efficiency (up to 43% isolated yields) and high optical purity (up to >99% ee). In addition, we also demonstrated that the bio-nitration method was able to tolerate the substrate at a high concentration of 1000 mM (150 g/L). Furthermore, representative synthesis of two optically active enantiomers of the ß-adrenergic blocker metoprolol was successfully achieved by utilizing the corresponding chiral ß-nitroalcohols as precursors.

Phase-Separated Dielectric Gels Based on Christiansen Effect.

Phase separation is a trivial phenomenon but a mature strategy in materials science. The flexible materials are provided toughness and strength by phase separation, yet there are few applications in optics and electronics industry. A novel phase-separated dielectric gel (PSDG) with a strong Christiansen effect is prepared via radical polymerization using hydroxyethyl methacrylate as a monomer, 4-cyano-4'-pentylbiphenyl and tributyl citrate as mixed solvents, and polyethylene glycol as a softener. The solvent ratios and ambient conditions can efficiently change the color of PSDG which makes it strongly selective for the wavelength of transmitted light. Besides, it has a high dielectric constant (10 at 1 kHz), sensitively responding to the electric field. The phase separation degree of PSDG varies with applied electric field, which will induce its transmittance alteration accordingly. The current field sensitive PSDG provides a novel idea for "smart windows". Additionally, varying the size and shape of the electrodes can precisely control the phase separation in PSDG and also enables the function of free writing on flexible materials. Therefore, the designed PSDG has great application potential for flexible touch and interesting interactions.

High Lithium Salt Content PVDF-Based Solid-State Composite Polymer Electrolyte Enhanced by h-BN Nanosheets.

Due to the unique safety qualities, solid composite polymer electrolyte (SCPE) has achieved considerable attentions to fabricate high-energy-density lithium metal batteries, but its overall performance still has to be improved. Herein, a high lithium salt content poly(vinylidene fluoride) (PVDF)-based SCPE was developed, enhanced by hexagonal boron nitride (h-BN) nanosheets, presenting perfect electrochemical performance, fast ion transport, and efficient inhibition of lithium dendrite growth. The optimized SCPE (PVDF-L70-B5) could deliver high ionic conductivity (2.98×10-4  S cm-1 ), ultra-high Li+ ion transfer number (0.62), wide electrochemical stability window (5.24 V), and strong mechanical strength (3.45 MPa) at room temperature. Density functional theory calculation further confirmed that the presence of h-BN could promote the dissociation of bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) and the rapid transfer of Li+ ions. As a result, the assembled symmetric Li/Li battery and asymmetric Li/LiFePO4 battery using PVDF-L70-B5 SCPEs both exhibited high reversible capacity, long-term cycle stability, and high-rate performance when cycled at 60 or 30 °C. The designed SCPEs will open up a new route to synthesize solid-state lithium batteries with high energy density and high safety.

Photoelastic Organogel with Multiple Stimuli Responses.

The photoelastic effect has many uses in mechanics today, but it is usually disregarded in flexible materials. Using 2-phenoxyethyl acrylate as a monomer and 4-cyano-4'-pentylbiphenyl (5CB) as a solvent, a multiple responsive photoelastic organogel (PO) with strong birefringence but low modulus is created. 5CB is a liquid crystal molecule that does not participate in the polymerization process and is always present as tiny molecules in the polymer. It endows the PO low modulus and high birefringence, as well as the ability to drive the birefringence using an electric field. This PO not only has high sensitivity and fast response as a photoelastic strain sensor, but also has a very sensitive response to heat, especially in the range of human body temperature. It also has a high dielectric constant and a strong correlation between the interference color and the applied electric field, allowing for easy writing and erasure of encrypted data. This unique multisignal response feature and low modulus that mimics human skin bring up new opportunities in the potential applications such as multiple information encryption, anticounterfeiting, and multifunctional wearable sensors.

Current-Density Regulating Lithium Metal Directional Deposition for Long Cycle-Life Li Metal Batteries.

Uncontrolled dendrite formation in the high energy density of lithium (Li) metal batteries (LMBs) may pose serious safety risks. While numerous studies have attempted to protect separators, these proposed methods fail to effectively inhibit upward dendrite growth that punctures through the separator. Here, we introduce a novel "orientated-growth" strategy that transfers the main depositional interface to the anode/current collector interface from the anode/separator interface. We placed a layer of cellulose/graphene carbon composite aerogel (CCA) between the current collector and the anode (LCL-bottom). This layer works as a charge organizer that induces a high current density and encourages Li to deposit at the anode/current collector interface. Both in situ and ex situ images of the electrode demonstrate that the anode part of the cell has been flipped; with the newly deposited particles facing the current collector and the smooth surface facing the separator. The electrode in half and full cells showed outstanding cyclic stability and rate capability, with the LCL-bottom/LFP full cell capable of maintaining 94 % of its initial capacity after 1000 cycles.