Ti─O─C Bonding at 2D Heterointerfaces of 3D Composites for Fast Sodium Ion Storage at High Mass Loading Level.

3D composite electrodes have shown extraordinary promise as high mass loading electrode materials for sodium ion batteries (SIBs). However, they usually show poor rate performance due to the sluggish Na+ kinetics at the heterointerfaces of the composites. Here, a 3D MXene-reduced holey graphene oxide (MXene-RHGO) composite electrode with Ti─O─C bonding at 2D heterointerfaces of MXene and RHGO is developed. Density functional theory (DFT) calculations reveal the built-in electric fields (BIEFs) are enhanced by the formation of bridged interfacial Ti─O─C bonding, that lead to not only faster diffusion of Na+ at the heterointerfaces but also faster adsorption and migration of Na+ on the MXene surfaces. As a result, the 3D composite electrodes show impressive properties for fast Na+ storage. Under high current density of 10 mA cm-2, the 3D MXene-RHGO composite electrodes with high mass loading of 10 mg cm-2 achieve a strikingly high and stable areal capacity of 3 mAh cm-2, which is same as commercial LIBs and greatly exceeds that of most reported SIBs electrode materials. The work shows that rationally designed bonding at the heterointerfaces represents an effective strategy for promoting high mass loading 3D composites electrode materials forward toward practical SIBs applications.

Construction of sub micro-nano-structured silicon based anode for lithium-ion batteries.

The significant volume change experienced by silicon (Si) anodes during lithiation/delithiation cycles often triggers mechanical-electrochemical failures, undermining their utility in high-energy-density lithium-ion batteries (LIBs). Herein, we propose a sub micro-nano-structured Si based material to address the persistent challenge of mechanic-electrochemical coupling issue during cycling. The mesoporous Si-based composite submicrospheres (M-Si/SiO2/CS) with a high Si/SiO2content of 84.6 wt.% is prepared by magnesiothermic reduction of mesoporous SiO2submicrospheres followed by carbon coating process. M-Si/SiO2/CS anode can maintain a high specific capacity of 740 mAh g-1at 0.5 A g-1after 100 cycles with a lower electrode thickness swelling rate of 63%, and exhibits a good long-term cycling stability of 570 mAh g-1at 1 A g-1after 250 cycles. This remarkable Li-storage performance can be attributed to the synergistic effects of the hierarchical structure and SiO2frameworks. The spherical structure mitigates stress/strain caused by the lithiation/delithiation, while the internal mesopores provide buffer space for Si expansion and obviously shorten the diffusion path for electrolyte/ions. Additionally, the amorphous SiO2matrix not only servers as support for structure stability, but also facilitates the rapid formation of a stable solid electrolyte interphase layer. This unique architecture offers a potential model for designing high-performance Si-based anode for LIBs.

2D Heterolayer-Structured MoSe2-Carbon with Fast Kinetics for Sodium-Ion Capacitors.

Two-dimensional (2D) layered MoSe2 has been demonstrated to be a promising electrode material for new energy storage systems. However, its nature of poor conductivity and the undesirable interlayer spacing hinder its further application. In this paper, a general and simple plasma-enhanced chemical vapor deposition method is proposed to produce 2D heterolayer-structured MoSe2-carbon (MoSe2/C) with carbon atoms inserted in the MoSe2 layers. After morphology optimization, when applying flat-type MoSe2/C-200 nanosheets with an enlarged interlayer spacing of 0.79 nm as the anode and activated carbon as the cathode, the assembled sodium-ion hybrid capacitors can reach a maximum energy/power density of 116.5 W h kg-1/107.5 W kg-1 and exhibit superior cycling durability (91.3% capacitance retention after 4000 cycles at 1 A g-1). The good electrochemical property can be ascribed to the enlarged interlayer spacing that can offer fast diffusion channels for Na ions, and the carbon layer sandwiched in the MoSe2 layer can not only enhance the electron transfer, accelerating the reaction kinetics, but also alleviate the volume change of MoSe2, ensuring the good stability of the electrode. The proposed approach can also be extended to other 2D transition metal chalcogenide (TMC) materials for constructing the TMC/C heterostructures for the application in energy storage systems.

Dual-functional ionic liquids additive enables dendrite-free Zn anode with ultra-long cycle life over one year.

Zn anodes suffer from the formation of uncontrolled dendrites aggravated by the uneven electric field and the insulating by-product accumulation in aqueous zinc-ion batteries (AZIBs). Here, an effective strategy implemented by 1-butyl-3-methylimidazolium hydrogen sulfate (BMIHSO4) additive is proposed to synergistically tune the crystallographic orientation of zinc deposition and suppress the formation of zinc hydroxide sulfate for enhancing the reversibility on Zn anode surface. As a competing cation, BMI+ is proved to preferably adsorb on Zn-electrode compared with H2O molecules, which shields the "tip effect" and inhibits the Zn-deposition agglomerations to inducing the horizontal growth along Zn (002) crystallographic texture. Simultaneously, the protonated BMIHSO4 additives could remove the detrimental OH- in real-time to fundamentally eliminate the accumulation of 6Zn(OH)2·ZnSO4·4H2O and Zn4SO4(OH)6·H2O on Zn anode surface. Consequently, Zn anode exhibits an ultra-long cycling stability of one year (8762 h) at 0.2 mA cm-2/0.2 mAh cm-2, 3600 h at 2 mA cm-2/2 mAh cm-2 with a high plating cumulative capacity of 3.6 Ah cm-2, and a high average Coulombic efficiency of 99.6 % throughout 1000 cycles. This work of regulating Zn deposition texture combined with eliminating notorious by-products could offer a desirable way for stabilizing the Zn-anode/electrolyte interface in AZIBs.

Effect of Nb on the Damping Property and Pseudoelasticity of a Porous Ni-Ti Shape Memory Alloy.

In order to develop novel high damping materials with excellent pseudoelasticity (PE) properties to meet the application requirements in aerospace, medical, military and other fields, porous Ni50.8Ti49.2 shape memory alloy (SMA) was prepared by the powder metallurgy method. Different contents of Nb element were added to regulate the microstructures. It was found that after adding the Nb element, the number of precipitates significantly decreased, and the Nb element was mainly distributed in the Ni-Ti matrix in the form of ß-Nb blocks surrounded by Nb-rich layers. Property tests showed that with the increase in Nb content, the damping and PE increased first and then decreased. When the Nb content reached 9.0 at.%, the highest damping and the best PE could be achieved. Compared with the porous Ni-Ti SMA without Nb addition, the damping and PE increased by 60% and 35%, respectively. Correlated mechanisms were discussed.

A Multidimensional Topotactic Host Composite Anode Toward Transparent Flexible Potassium-Ion Microcapacitors.

Transparent flexible supercapacitors (TFSCs) are a tantalizing power supplier for future transparent flexible electronics. However, their energy density is far behind a practical level while maintaining high transparency. We report here a transparent flexible potassium-ion microcapacitor, and its high energy density (15.5 µWh cm-2) roots in the battery-supercapacitor hybrid storage mechanism and much enlarged working voltage (3 V), outperforming the state-of-the-art TFSC, which is generally based on an aqueous electrolyte and an asymmetric pseudocapacitive mechanism. From an electrode material perspective, a multidimensional topotactic host composite anode is designed in which the component not only performs energy storage by synchronous and reversible uptake of potassium ions and electrons into its host structure, but also mutually compensates individual weakness in functional and structural aspects, efficiently constructing a three-dimensional potassium-ion diffusion and electron transport system. This conceptual exhibition provides design principles at material and device levels for high-performance TFSCs.

Flexible Electron-Rich Ion Channels Enable Ultrafast and Stable Aqueous Zinc-Ion Storage.

Aqueous zinc-ion batteries (ZIBs) are regarded as a promising candidate for ultrafast charge storage owing to the high ionic conductivity of aqueous electrolytes and high theoretical capacity of zinc metal anodes. However, the strong electrostatic interaction between high-charge-density zinc ions and host materials generally leads to sluggish ion-transport kinetics and structural collapse of rigid cathode materials during the charge/discharge process, so searching for suitable cathode materials for ultrafast and long-term stable ZIBs remains a great challenge. Herein, flexible electron-rich ion channels enabling fast-charging and stable aqueous ZIBs have been demonstrated. Because of the nitrogen-rich conjugated structure of organic phenazine (PNZ) molecules, electron-rich ion channels are formed with the C═N redox centers situated on the channel surface, where zinc ions can transport rapidly and react with active moieties directly. Meanwhile, the π-conjugated systems and inherent flexibility of PNZ molecules can accommodate rapid strain changes and maintain their structural stability during zinc-ion intercalation/deintercalation. Consequently, they exhibit a high capacity of 94.2 mAh g-1 at an ultrahigh rate of 700C (208.6 A g-1) and an ultralong life over 100,000 cycles at 100C, which are superior to those of previously reported aqueous ZIBs. Our work presents a new way for developing ultrafast and ultrastable aqueous ZIBs.

Low-Bandgap Se-Deficient Antimony Selenide as a Multifunctional Polysulfide Barrier toward High-Performance Lithium-Sulfur Batteries.

The shuttling behavior and sluggish conversion kinetics of the intermediate lithium polysulfides (LiPSs) represent the main obstructions to the practical application of lithium-sulfur (Li-S) batteries. Herein, an anion-deficient design of antimony selenide (Sb2 Se3- x ) is developed to establish a multifunctional LiPS barrier toward the inhibition of polysulfide shuttling and enhancement of battery performance. The defect chemistry in the as-developed Sb2 Se3- x promotes the intrinsic conductivity, strengthens the chemical affinity to LiPSs, and catalyzes the sulfur electrochemical conversion, which are verified by a series of computational and experimental results. Attributed to these unique superiorities, the obtained LiPS barrier efficiently promotes and stabilizes the sulfur electrochemistry, thus enabling excellent Li-S battery performance, e.g., outstanding cyclability over 500 cycles at 1.0 C with a minimum capacity fading rate of 0.027% per cycle, a superb rate capability up to 8.0 C, and a high areal capacity of 7.46 mAh cm-2 under raised sulfur loading. This work offers a defect engineering strategy toward fast and durable sulfur electrochemistry, holding great promise in developing practically viable Li-S batteries as well as enlightening the material design of related energy storage and conversion systems.

Bioinspired Pretextured Reduced Graphene Oxide Patterns with Multiscale Topographies for High-Performance Mechanosensors.

Highly sensitive mechanical sensing is vital for the emerging field of skin mimicry and wearable healthcare systems. To date, it remains a big challenge to fabricate mechanosensors with both high sensitivity and a wide sensing range. In nature, slit sensilla are crack-shaped sensory organs of arachnids, which are highly sensitive to tiny external mechanical stimuli. Here, inspired by the geometry of slit sensilla, a concept is developed that pretextures reduced graphene oxide (RGO) nanocoating into multiscale topographies with agminated crumples and interlaced cracks (crumpled & cracked RGO) through an efficient and scalable mechanically driven process. Both the sensitivity and the workable range can be facilely tuned by adjusting the crack density. The resulting mechanosensor exhibits a comprehensive superior performance including high sensitivity (a gauge factor of 205 to 3256), a wide and tunable sensing range (from 0-40 to 0-180%), long-term stability (over 5000 cycles), and multiple sensing functions. Based on its excellent performances, the mechanosensor can be used as a wearable electronic to in situ monitor subtle physiological signals and vigorous body actions. The rationally designed crumpled & cracked RGO provides a promising platform for artificial electronic skin and portable healthcare systems.