Bifunctional Edge-Rich Nitrogen Doped Porous Carbon for Activating Oxygen and Sulfur

Oxygen reduction reaction (ORR) and sulfur reduction reaction (SRR) play key roles in advanced batteries. However, they both suffer from sluggish reaction kinetics. Here, an interesting nitrogen doped porous carbon material that can simultaneously activate oxygen and sulfur is reported. The carbon precursor is a nitrogen containing covalent organic framework (COF), constituting periodically stacked 2D sheets. The COF structure is well preserved upon pyrolysis, resulting in the formation of edge-rich porous carbon with structure resembling stacked holey graphene. The nitrogen containing groups in the COF are decomposed into graphitic and pyridinic nitrogen during pyrolysis. These edge sites and uniform nitrogen doping endow the carbon product with high intrinsic catalytic activities toward ORR and SRR. The COF derived carbon delivers outstanding performances when assembling as cathodes in the Li-S and Li-O₂ batteries. Simultaneous activation of oxygen and sulfur also enables a new battery chemistry. A proof-of-concept Li-S/O₂ hybrid battery is assembled, delivering a large specific capacity of 2,013 mAh g⁻¹. This study may inspire novel battery designs based on oxygen and sulfur chemistry.     

Pre-Protonated Vanadium Hexacyanoferrate for High Energy-Power and Anti-Freezing Proton Batteries

Proton batteries have been considered as an innovative energy storage technology owing to their high safety and cost-effectiveness. However, the development of fast-charging proton batteries with high energy/power density is greatly limited by feasible material selection. Here, the pre-protonated vanadium hexacyanoferrate (H-VHCF) is developed as a proton cathode material to alleviate the capacity loss of proton-free electrode materials during electrochemical tests. The pre-protonation process realizes fast and long-distance transport of protons by shortening diffusion path and reducing migration barriers. Benefitting from the enhanced hydrogen bonding network combined with dual redox reactions of V and Fe in protonated H-VHCF cathode, a high energy density of 74 Wh kg⁻¹ at 1.1 kW kg⁻¹, and a maximum power density of 54 kW kg⁻¹ at 65 Wh kg⁻¹ is achieved for the asymmetric proton batteries coupling with MoO₃/MXene anode. Proton transport and double oxidation-reduction center are verified by theoretical calculations and ex situ experimental measurements. Considering the anti-freezing availability of proton batteries, 82.5% of its initial capacity is maintained after 10000 cycles under −40 °C at 0.5 A g⁻¹. As a proof-of-concept, flexible device fabricated by optimized electrodes and hydrogel electrolytes can power up a light-emitting diode even under a bent state.     

Cell Development Enhanced Bionic Silk Hydrogel on Remodeling Immune Pathogenesis of Spinal Cord Injury via M2 Polarization of Microglial

Due to the complex spatial-temporal pathophysiology of spinal cord injury (SCI), effective modulation of SCI-specific inflammatory pathogenesis to achieve desirable therapeutic effects on functional recovery still remains challenging. Herein, cell-enhanced photocrosslinked silk fibroin hydrogels with extracellular matrix-mimicking cues of mechanical properties and RGD (Arg-Gly-Asp) signals are gelled in situ to fill the lesion site to modulate injury-induced neuroinflammation and promote neurite regrowth after SCI. The bionic hydrogel system provides biomimetic mechanical cues to promote neuronal differentiation of neural stem/progenitor cells (NPCs) and neurite growth by activating YAP nuclear expression. Importantly, favored by the strong capacity of silk fibroin hydrogels on macrophage/microglia recruitment, NPCs encapsulated hydrogel (NPCs@SFRGD0.1) effectively promotes recruited macrophages/microglia to M2 polarization in the lesion site by releasing S100A4 and thereby remodels the inflammatory microenvironment after SCI. Moreover, NPCs@SFRGD0.1 successfully reduces glial scar formation and accelerates corticospinal tract axon regrowth to improve locomotor recovery. Overall, this work contributes to illustrating the therapeutic mechanism of NPCs development based biomaterial therapies on modulating inflammatory microenvironment and this NPCs enhanced silk fibroin hydrogel provides a promising therapeutic strategy for SCI.     

Electret Molecular Configuration Induced Programmable Photonic Memory for Advanced Logic Operation and Data Encryption

Nonvolatile organic photonic transistor (OPT) memories have attracted widespread attention due to their nondestructive readout, remote controllability, and robust tunability. Developing electrets with similar molecular structures but different memory behaviors and light-responsive features is crucial for light-wavelength-modulated data encryption. However, reported OPT memories have yet to meet this challenge. Here a new electret molecule (“H-PDI”) is developed via reconfiguring the linear perylene diimide molecule (“L-PDI”) to a helical shape. Respectively incorporating H-PDI and L-PDI into the floating gate layer results to H-PDI OPT and L-PDI OPT. Attributing to their remarkably different electronic structures and energy bandgaps, H-PDI OPT and L-PDI OPT preferably respond to 405 and 532 nm light irradiation, respectively. Upon electrical programming, data can be written and stored in both memories with good retention features and a high “1”/“0” state current ratio over 10⁵, though the data can only be erased by light with correct wavelengths, rather than the electrical field. Moreover, data stored in a memory array consisting of both H-PDI OPT and L-PDI OPT can only be read out by correct inputs, and wrong inputs will lead to highly deceptive outputs. This study provides a general design strategy of OPT for advanced data encryption and protection.     

A Low-Hysteresis and Highly Stretchable Ionogel Enabled by Well Dispersed Slidable Cross-Linker for Rapid Human-Machine Interaction

Ionic conductive soft materials for mimicking human skin are a promising topic since they can be thought of as a possible basis for biomimetic sensing. In pursuit of devices with a long working range and low signal delay, conductive materials with low hysteresis and good stretchability are highly demanded. To overcome the challenges of highly stretchable conductive materials with good resilience, herein a chemical design is proposed where polyrotaxanes act as topological cross-linkers to enhance the stretchability by sliding-induced reduced stress concentration while the compatible ionic liquid is introduced as a dispersant for low hysteresis. The obtained ionogels exhibit versatile properties more than low hysteresis (residual strain = 7%) and good stretchability (550%), and also anti-fatigue, biocompatibility, and good adhesion. The low hysteresis is attributed to lower energy dissipation from the well-dispersed polyrotaxanes by compatible ionic liquids. The mechanism provides a new insight in fabricating highly stretchable and low-hysteresis slide-ring materials. Furthermore, the conductivity of the ionogels and their responses to strains and temperatures are measured. Benefiting from the good conductivity and low hysteresis, the ionogel is applied to develop a wireless communication system to realize rapid human-machine interactions.     

High-Efficiency Organic Solar Cells Enabled by Chalcogen Containing Branched Chain Engineering: Balancing Short-Circuit Current and Open-Circuit Voltage,Enhancing Fill Factor

The elaborate balance between the open-circuit voltage (V_OC) and the short-circuit current density (J_SC) is critical to ensure efficient organic solar cells (OSCs). Herein, the chalcogen containing branched chain engineering is employed to address this dilemma. Three novel nonfullerene acceptors (NFAs), named BTP-2O , BTP-O-S , and BTP-2S , featuring different peripheral chalcogen containing branched chains are synthesized. Compared with symmetric BTP-2O and BTP-2S grafting two alkoxy or alkylthio branched chains, the asymmetric BTP-O-S grafting one alkoxy and one alkylthio branched chains shows mediate absorption range, applicable miscibility, and favorable crystallinity. Benefiting from the enhanced π–π stacking and charge transport, an optimal power conversion efficiency (PCE) of 17.3% is obtained for the PM6: BTP-O-S -based devices, with a good balance between V_OC (0.912 V) and J_SC (24.5 mA cm⁻²), and a high fill factor (FF) of 0.775, which is much higher than those of BTP-2O (16.1%) and BTP-2S -based (16.4%) devices. Such a result represents one of the highest efficiencies among the binary OSCs with V_OC surpassing 0.9 V. Moreover, the BTP-O-S -based devices fabricated by using green solvent yield a satisfactory PCE of 17.1%. This work highlights the synergistic effect of alkoxy and alkylthio branched chains for high-performance OSCs by alleviating voltage loss and enhancing FF.     

Tetrabutylammonium Bromide Functionalized Ti3C2Tx MXene as Versatile Cathode Buffer Layer for Efficient and Stable Inverted Perovskite Solar Cells

2D Ti₃C₂T_x MXene, possessing facile preparation, high electrical conductivity, flexibility, and solution processability, shows good application potential for enhancing device performance of perovskite solar cells (PVSCs). In this study, tetrabutylammonium bromide functionalized Ti₃C₂T_x (TBAB-Ti₃C₂T_x) is developed as cathode buffer layer (CBL) to regulate the PCBM/Ag cathode interfacial property for the first time. By virtue of the charge transfer from TBAB to Ti₃C₂T_x demonstrated by electron paramagnetic resonance and density functional theory, the TBAB-Ti₃C₂T_x CBL with high electrical conductivity exhibits significantly reduced work function of 3.9 eV, which enables optimization of energy level alignment and enhancement of charge extraction. Moreover, the TBAB-Ti₃C₂T_x CBL can effectively inhibit the migration of iodine ions from perovskite layer to Ag cathode, which synergistically suppresses defect states and reduce charge recombination. Consequently, utilizing MAPbI₃ perovskite without post-treatment, the TBAB-Ti₃C₂T_x based device exhibits a dramatically improved power conversion efficiency of 21.65% with significantly improved operational stability, which is one of the best efficiencies reported for the devices based on MAPbI₃/PCBM with different CBLs. These results indicate that TBAB-Ti₃C₂T_x shall be a promising CBL for high-performance inverted PVSCs and inspire the further applications of quaternary ammonium functionalized MXenes in PVSCs.     

An Intrinsically Nonflammable Electrolyte for Prominent-Safety Lithium Metal Batteries with High Energy Density and Cycling Stability

Nex-generation high-energy-density storage battery, assembled with lithium (Li)-metal anode and nickel-rich cathode, puts forward urgent demand for advanced electrolytes that simultaneously possess high security, wide electrochemical window, and good compatibility with electrode materials. Herein an intrinsically nonflammable electrolyte is designed by using 1 M lithium difluoro(oxalato)borate (LiDFOB) in triethyl phosphate (TEP) and N-methyl-N-propyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [Pyr₁₃][TFSI] ionic liquid (IL) solvents. The introduction of IL can bring plentiful organic cations and anions, which provides a cation shielding effect and regulates the Li⁺ solvation structure with plentiful Li⁺-DFOB⁻ and Li⁺-TFSI⁻ complexes. The unique Li⁺ solvation structure can induce stable anion-derived electrolyte/electrode interphases, which effectively inhibit Li dendrite growth and suppress side reactions between TEP and electrodes. Therefore, the LiNi_0.9Co_0.05Mn_0.05O₂ (NCM90)/Li coin cell with this electrolyte can deliver stable cycling even under 4.5 V and 60 °C. Moreover, a Li-metal battery with thick NCM90 cathode (≈ 15 mg cm⁻²) and thin Li-metal anode (≈ 50 µm) (N/P ≈ 3), also reveals stable cycling performance under 4.4 V. And a 2.2 Ah NCM90/Li pouch cell can simultaneously possess prominent safety with stably passing the nail penetration test, and high gravimetric energy density of 470 Wh kg⁻¹ at 4.4 V.     

A Visible and Near-Infrared Light-Fueled Omnidirectional Twist-Bend Crawling Robot

In recent years, although light-driven soft actuators have attracted intense scientific attention and achieved remarkable progress, the design and construction of an intelligent robotic system with maneuverability, self-adaptability, untethered control, and greater freedom of action, in particular the omnidirectional motion capability on a plane, remains challenging. Herein, four types of photo-thermal fillers and an unprecedented twist-bend actuation mode is introduced into a liquid crystal elastomer-based soft robot. The obtained twist-bend crawling robot not only exhibits in situ rotation, four-way turning, and four-way linear motion under light irradiation with four wavelength bands (520, 655, 808, and 980 nm), but also demonstrates the ability to avoid obstacles in complex geographical environments. This work may bring a new perspective for fabrication and development of soft robots that can adapt to dynamic and complex environmental conditions.     

Intercalative Motifs-Induced Space Confinement and Bonding Covalency Enhancement Enable Ultrafast and Large Sodium Storage

Alloying-type metal sulfides with high theoretical capacities are promising anodes for sodium-ion batteries, but suffer from sluggish sodiation kinetics and huge volume expansion. Introducing intercalative motifs into alloying-type metal sulfides is an efficient strategy to solve the above issues. Herein, robust intercalative In S motifs are grafted to high-capacity layered Bi₂S₃ to form a cation-disordered (BiIn)₂S₃, synergistically realizing high-rate and large-capacity sodium storage. The In S motif with strong bonding serves as a space-confinement unit to buffer the volume expansion, maintaining superior structural stability. Moreover, the grafted high-metallicity Indium increases the bonding covalency of Bi S, realizing controllable reconstruction of Bi S bond during cycling to effectively prevent the migration and aggregation of atomic Bi. The novel (BiIn)₂S₃ anode delivers a high capacity of 537 mAh g⁻¹ at 0.4 C and a superior high-rate stability of 247 mAh g⁻¹ at 40 C over 10000 cycles. Further in situ and ex situ characterizations reveal the in-depth reaction mechanism and the breakage and formation of reversible Bi S bonds. The proposed space confinement and bonding covalency enhancement strategy via grafting intercalative motifs can be conducive to developing novel high-rate and large-capacity anodes.