Sodium-ion batteries operating at room temperature have emerged as a generation of energy storage devices to replace lithium-ion batteries; however, they are limited by a lack of anode materials with both an adequate lifespan and excellent rate capability. To address this issue, we developed Nb 2 CT x MXene-framework MoS 2 nanosheets coated with carbon (Nb 2 CT x @MoS 2 @C) and constructed a robust threedimensional cross-linked structure. In such a design, highly conductive Nb 2 CT x MXene nanosheets prevent the restacking of MoS 2 sheets and provide efficient channels for charge transfer and diffusion. Additionally, the hierarchical carbon coating has a certain level of volume elasticity and excellent electrical conductivity to guarantee the intercalation of sodium ions, facilitating both fast kinetics and long-term stability. As a result, the Nb 2 CT x @MoS 2 @C anode delivers an ultrahigh reversible capacity of 530 mA h g −1 at 0.1 A g −1 after 200 cycles and very long cycling stability with a capacity of 403 mA h g −1 and only 0.01% degradation per cycle for 2000 cycles at 1.0 A g −1 . Moreover, this anode has an outstanding capacity retention rate of approximately 88.4% from 0.1 to 1 A g −1 in regard to rate performance. Most importantly, the Nb 2 CT x @MoS 2 @C anode can realize a quick charge and discharge at current densities of 20 or even 40 A g −1 with capacities of 340 and 260 mAh g −1 , respectively, which will increase the number of practical applications for sodium-ion batteries. KEYWORDS: Nb 2 CT x @MoS 2 @C, Nb 2 CT x MXene, 3D network, sodium-ion batteries, high rate performance, high capacity

Accurate and continuous detection of physiological signals without the need for an external power supply is a key technology for realizing wearable electronics as next‐generation biomedical devices. Herein, it is shown that a MXene/black phosphorus (BP)‐based self‐powered smart sensor system can be designed by integrating a flexible pressure sensor with direct‐laser‐writing micro‐supercapacitors and solar cells. Using a layer‐by‐layer (LbL) self‐assembly process to form a periodic interleaving MXene/BP lamellar structure results in a high energy‐storage capacity in a direct‐laser‐writing micro‐supercapacitor to drive the operation of sensors and compensate the intermittency of light illumination. Meanwhile, with MXene/BP as the sensitive layer in a flexible pressure sensor, the pressure sensitivity of the device can be improved to 77.61 kPa–1 at an optimized elastic modulus of 0.45 MPa. Furthermore, the smart sensor system with fast response time (10.9 ms) shows a real‐time detection capability for the state of the human heart under physiological conditions. It is believed that the proposed study based on the design and integration of MXene materials will provide a general platform for next‐generation self‐powered electronics.

Although Mn2+ additive alleviates the dissolution issue of Mn-based cathodes in aqueous zinc-ion batteries (ZIBs), problems including complex side reactions and abnormal capacity fluctuation pose new challenges for their large-scale...

MXenes are an emerging class of 2D transition metal carbides and nitrides. They have been widely used in flexible electronics owing to their excellent conductivity, mechanical flexibility, and water dispersibility. In this study, the electrode and active layer applications of MXene materials in electronic skins are realized. By utilizing vacuum filtration technology, few‐layer MXene electrodes are integrated onto the top and bottom surfaces of the 3D polyacrylonitrile (PAN) network to form a stable electronic skin. The fabricated flexible device with Ti3C2Tx MXene electrodes outperforms those with other electrodes and exhibits excellent device performance, with a high sensitivity of 104.0 kPa−1, fast response/recovery time of 30/20 ms, and a low detection limit of 1.5 Pa. Furthermore, the electrode and the constructed MXene/PAN‐based flexible pressure sensor exhibit robust mechanical stability and can survive 240 bending cycles. Such a robust, flexible device can be enlarged or folded like a jigsaw puzzle or origami and transformed from 2D to 3D structures; moreover, it can detect tiny movements of human muscles, such as movements corresponding to sound production and intense movements during bending of fingers.

As a typical family of two-dimensional (2D) materials, MXenes present physiochemical properties and potential for use in energy storage applications. However, MXenes suffer some of the inherent disadvantages of 2D materials, such as severe restacking during processing and service and low capacity of energy storage. Herein, a MXene@N-doped carbonaceous nanofiber structure is designed as the anode for high-performance sodium-and potassium-ion batteries through an in situ bioadsorption strategy; that is, Ti 3 C 2 T x nanosheets are assembled onto Aspergillus niger biofungal nanoribbons and converted into a 2D/1D heterostructure. This microorganism-derived 2D MXene-1D N-doped carbonaceous nanofiber structure with fully opened pores and transport channels delivers high reversible capacity and long-term stability to store both Na + (349.2 mAh g −1 at 0.1A g −1 for 1000 cycles) and K + (201.5 mAh g −1 at 1.0 A g −1 for 1000 cycles). Ion-diffusion kinetics analysis and density functional theory calculations reveal that this porous hybrid structure promotes the conduction and transport of Na and K ions and fully utilizes the inherent advantages of the 2D material. Therefore, this work expands the potential of MXene materials and provides a good strategy to address the challenges of 2D energy storage materials. KEYWORDS: biosorption, Ti 3 C 2 T x MXenes, porous hybrid fibers, sodium-ion batteries, potassium-ion batteries, density functional theory calculations

Highlights Unique “Janus” interfacial assemble strategy of 2D MXene nanosheets was proposed firstly. Ternary heterostructure consisting of high capacity transitional metal chalcogenide, high conductive 2D MXene and N rich fungal carbonaceous matrix was achieved for larger radius Na/K ions storages. The highly accessible surfaces and interfaces of the strongly coupled 2D based ternary heterostructures provide superb surficial pseudocapacitive storages for both Na and K ions with low energy barriers was verified. Abstract Combining with the advantages of two-dimensional (2D) nanomaterials, MXenes have shown great potential in next generation rechargeable batteries. Similar with other 2D materials, MXenes generally suffer severe self-agglomeration, low capacity, and unsatisfied durability, particularly for larger sodium/potassium ions, compromising their practical values. In this work, a novel ternary heterostructure self-assembled from transition metal selenides (MSe, M = Cu, Ni, and Co), MXene nanosheets and N-rich carbonaceous nanoribbons (CNRibs) with ultrafast ion transport properties is designed for sluggish sodium-ion (SIB) and potassium-ion (PIB) batteries. Benefiting from the diverse chemical characteristics, the positively charged MSe anchored onto the electronegative hydroxy (–OH) functionalized MXene surfaces through electrostatic adsorption, while the fungal-derived CNRibs bonded with the other side of MXene through amino bridging and hydrogen bonds. This unique MXene-based heterostructure prevents the restacking of 2D materials, increases the intrinsic conductivity, and most importantly, provides ultrafast interfacial ion transport pathways and extra surficial and interfacial storage sites, and thus, boosts the high-rate storage performances in SIB and PIB applications. Both the quantitatively kinetic analysis and the density functional theory (DFT) calculations revealed that the interfacial ion transport is several orders higher than that of the pristine MXenes, which delivered much enhanced Na+ (536.3 mAh g−1@ 0.1 A g−1) and K+ (305.6 mAh g−1@ 1.0 A g−1 ) storage capabilities and excellent long-term cycling stability. Therefore, this work provides new insights into 2D materials engineering and low-cost, but kinetically sluggish post-Li batteries.

Flexible pressure sensors may be used in electronic skin (e-skin), artificial intelligence devices, and disease diagnosis, which require a large response range and high sensitivity. An appropriate design of the structure of the active layer can help effectively solve this problem. Herein, we aim at developing a wearable pressure sensor using the MXene/ZIF-67/polyacrylonitrile (PAN) nanofiber film, fabricated by electrospinning technology. Owing to the rough structure and three-dimensional network architecture, the MXene/ZIF-67/PAN film-based device displays a broad working range (0–100 kPa), good sensitivity (62.8 kPa–1), robust mechanical stability (over 10,000 cycles), and fast response/recovery time (10/8 ms). Moreover, the fabricated pressure sensors can be used to detect and differentiate between different body motion information, including elbow bending, finger movements, and wrist pulses. Overall, this design of a rough three-dimensional conductive network structure shows potential in the field of wearable electronics and medical devices.

widely used alkali metal; however, it will be likely replaced with other alkali elements in the foreseeable future due to the limited Li reserves in the Earth's crust. [2] Therefore, the development of next-generation cost-effective sustainable energy storage system represents an urgent task. Sodium and potassium metals with relatively large ionic radii and electronic structures similar to that of Li have become promising candidates as the anode materials of alkali-metal-ion batteries because of their abundant reserves, high theoretical capacities, and low redox potentials close to Li + /Li. [3,4] Unfortunately, the high repulsive forces generated during the ion insertion and extraction processes occurring in sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) significantly limit their large-scale commercial applications. Therefore, it is necessary to identify suitable host materials for the both the larger sodium ions (Na + ) and potassium ions (K + ).The convergence of biological and synthetic materials is a cutting-edge subject that offers significant potential to develop bionic hybrid materials with improved properties, especially in the context of energy storage. [5,6] With unique functions, the 1D hierarchical nanostructure is one of the most promising type of high efficiency materials. This type of Owing to their cost-effectiveness and high energy density, sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are becoming the leading candidates for the next-generation energy-storage devices replacing lithiumion batteries. In this work, a novel Fe x−1 Se x heterostructure is prepared on fungus-derived carbon matrix encapsulated by 2D Ti 3 C 2 T x MXene highly conductive layers, which exhibits high specific sodium ion (Na + ) and potassium ion (K + ) storage capacities of 610.9 and 449.3 mAh g −1 at a current density of 0.1 A g −1 , respectively, and excellent capacity retention at high chargedischarge rates. MXene acts as conductive layers to prevent the restacking and aggregation of Fe x−1 Se x sheets on fungus-derived carbonaceous nanoribbons, while the natural fungus functions as natural nitrogen/carbon source to provide bionic nanofiber network structural skeleton, providing additional accessible pathways for the high-rate ion transport and satisfying surfacedriven contribution ratios at high sweep rates for both Na/K ions storages. In addition, in situ synchrotron diffraction and ex situ X-ray photoelectron spectroscopy measurements are performed to reveal the mechanisms of storage and de-/alloying conversion process of Na + in the Fe x−1 Se x /MXene/carbonaceous nanoribbon heterostructure. As a result, the assembled Na/K full cells containing MXene-supported Fe x−1 Se x @carbonaceous anodes possess stable large-ion storage capabilities.