Pristine Titanium Carbide MXene Films with Environmentally Stable Conductivity and Superior Mechanical Strength

2D titanium carbide (Ti₃C₂T_x MXene) has potential application in flexible/transparent conductors because of its metallic conductivity and solution processability. However, solution‐processed Ti₃C₂T_x films suffer from poor hydration stability and mechanical performance that stem from the presence of intercalants, which are unavoidably introduced during the preparation of Ti₃C₂T_x suspension. A proton acid colloidal processing approach is developed to remove the extrinsic intercalants in Ti₃C₂T_x film materials, producing pristine Ti₃C₂T_x films with significantly enhanced conductivity, mechanical strength, and environmental stability. Typically, pristine Ti₃C₂T_x films show more than twofold higher conductivity (10 400 S cm^?1 vs 4620 S cm^?1) and up to 11‐ and 32‐times higher strength and strain energy at failure (112 MPa, 1,480 kJ m^?3, vs 10 MPa, 45 kJ m^?3) than films prepared without proton acid processing. Simultaneously, the conductivity and mechanical integrity of pristine films are also largely retained during the long‐term storage in H₂O/O₂ environment. The improvement in mechanical performance and conductivity is originated from the intrinsic strong interaction between Ti₃C₂T_x layers, and the absence of extrinsic intercalants makes pristine Ti₃C₂T_x films stable in humidity by blocking the intercalation of H₂O/O₂. This method makes the material more competitive for real‐world applications such as electromagnetic interference shielding.     

Flexible Ti3C2Tx@Al electrodes with Ultrahigh Areal Capacitance: In Situ Regulation of Interlayer Conductivity and Spacing

Although Ti₃C₂ MXene has shown great potential in energy storage field, poor conductivity and restacking between MXene flakes seriously hinders the maximization of its capacitance. Herein, a new strategy to solve the problems is developed. Gallery Al atoms in Ti₃AlC₂ are partially removed by simple hydrothermal etching to get Ti₃C₂T_x reserving appropriate Al interlayers (Ti₃C₂T_x@Al). Ti₃C₂T_x@Al keeps stable layered structure rather than isolated Ti₃C₂T_x flakes, which avoids flake restacking. The removal of partial Al frees up space for easy electrolyte infiltration while the reserved Al as “electron bridges” ensures high interlayer conductivity. As a result, the areal capacitance reaches up to 1087 mF cm^?2 at 1 mA cm^?2 and over 95% capacitance is maintained after 6000 cycles. The all‐solid‐state supercapacitor (ASSS) based on Ti₃C₂T_x@Al delivers a high capacitance of 242.3 mF cm^?2 at 1 mV s^?1 and exhibits stable performance at different bending states. Two ASSSs in tandem can light up a light‐emitting diode under the planar or wrapping around an arm. The established strategy provides a new avenue to improve capacitance performances of MXenes.     

Stamping of Flexible,Coplanar Micro‐Supercapacitors Using MXene Inks

The fast growth of portable smart electronics and internet of things have greatly stimulated the demand for miniaturized energy storage devices. Micro‐supercapacitors (MSCs), which can provide high power density and a long lifetime, are ideal stand‐alone power sources for smart microelectronics. However, relatively few MSCs exhibit both high areal and volumetric capacitance. Here rapid production of flexible MSCs is demonstrated through a scalable, low‐cost stamping strategy. Combining 3D‐printed stamps with arbitrary shapes and 2D titanium carbide or carbonitride inks (Ti₃C₂T_x and Ti₃CNT_x, respectively, known as MXenes), flexible all‐MXene MSCs with controlled architectures are produced. The interdigitated Ti₃C₂T_x MSC exhibits high areal capacitance: 61 mF cm^?2 at 25 µA cm^?2 and 50 mF cm^?2 as the current density increases by 32 fold. The Ti₃C₂T_x MSCs also showcase capacitive charge storage properties, good cycling lifetime, high energy and power densities, etc. The production of such high‐performance Ti₃C₂T_x MSCs can be easily scaled up by designing pad or cylindrical stamps, followed by a cold rolling process. Collectively, the rapid, efficient production of flexible all‐MXene MSCs with state‐of‐the‐art performance opens new exciting opportunities for future applications in wearable and portable electronics.     

Engineering the Interlayer Spacing by Pre-Intercalation for High Performance Supercapacitor MXene Electrodes in Room Temperature Ionic Liquid

MXenes exhibit excellent capacitance at high scan rates in sulfuric acid aqueous electrolytes, but the narrow potential window of aqueous electrolytes limits the energy density. Organic electrolytes and room-temperature ionic liquids (RTILs) can provide higher potential windows, leading to higher energy density. The large cation size of RTIL hinders its intercalation in-between the layers of MXene limiting the specific capacitance in comparison to aqueous electrolytes. In this work, different chain lengths alkylammonium (AA) cations are intercalated into Ti₃C₂T_x, producing variation of MXene interlayer spacings (d-spacing). AA-cation-intercalated Ti₃C₂T_x (AA-Ti₃C₂), exhibits higher specific capacitances, and cycling stabilities than pristine Ti₃C₂T_x in 1 m 1-ethly-3-methylimidazolium bis-(trifluoromethylsulfonyl)-imide (EMIMTFSI) in acetonitrile and neat EMIMTFSI RTIL electrolytes. Pre-intercalated MXene with an interlayer spacing of ≈2.2 nm, can deliver a large specific capacitance of 257 F g⁻¹ (1428 mF cm⁻² and 492 F cm⁻³) in neat EMIMTFSI electrolyte leading to high energy density. Quasi elastic neutron scattering and electrochemical impedance spectroscopy are used to study the dynamics of confined RTIL in pre-intercalated MXene. Molecular dynamics simulations suggest significant differences in the structures of RTIL ions and AA cations inside the Ti₃C₂T_x interlayer, providing insights into the differences in the observed electrochemical behavior.     

Strategy Toward Semiconducting Ti3C2Tx-MXene: Phenylsulfonic Acid Groups Modified Ti3C2Tx as Photosensitive Material for Flexible Visual Sensory-Neuromorphic System

The excellent electronic and electrochemical properties make 2D MXenes suitable candidates for sensors, batteries, and supercapacitors. However, the metallic-like behavior of MXenes hinders their potential for optoelectronic devices such as photodetectors. In this study, the band gap of metalloid Ti₃C₂T_x MXene is successfully opened to 1.53 eV with phenylsulfonic acid groups and realized a transistor and high-performance near-infrared photodetector array for a flexible vision sensory-neuromorphic system. The phenylsulfonic acid groups modified Ti₃C₂T_x MXene (S-Ti₃C₂T_x)-based flexible photodetector has a maximum responsivity of 8.50×10² A W⁻¹ and a detectivity of 3.69×10¹¹ Jones under 1064 nm laser irradiation. Moreover, the fabricated flexible vision sensory-neuromorphic system for image recognition realizes a high recognition rate >0.99, leading to great potential in the field of biological visual simulation and biomimetic eye. Besides conventional devices with Au as the conductive electrodes, all Ti₃C₂T_x MXene-based devices are also fabricated with S-Ti₃C₂T_x as the photosensitive material and unmodified Ti₃C₂T_x as the conductive electrodes, exhibiting comparable optoelectronic performances.     

Bimetal Organic Framework–Ti3C2Tx MXene with Metalloporphyrin Electrocatalyst for Lithium–Oxygen Batteries

The gravest oxidation of MXenes has become a critical problem due to the formation of metal oxides, leading to the loss of their intrinsic properties. Herein, bimetallic cobalt–manganese organic framework (CMT) directly grown on a Ti₃C₂T_x MXene sheet via solvothermal treatment to obtain strong oxidation resistance in an open structured application and to enhance electrocatalytic properties for oxygen evolution and reduction reaction is reported. Inspired by ligand chemistry, the carboxyl acids in tetrakis(4–carboxyphenyl)porphyrin acting as an organic linker are grafted with the surface terminators of Ti₃C₂T_x MXene through the Fischer esterification and substitution reaction of fluorine, thereby greatly enhancing the antioxidation stability. Furthermore, the as-formed metalloporphyrin structure and unpaired electrons, produced between CMT and Ti₃C₂T_x MXene during solvothermal treatment, improve their electrocatalytic activity, durability, and electrical conductivity through an electron hopping mechanism. Consequently, the CMT@MXene demonstrates high stability as a bifunctional electrocatalyst at a fixed specific capacity of 1000 mAh g⁻¹ and a current density of 500 mA g⁻¹ for 247 cycles in lithium–oxygen (Li O₂) battery. This approach suggests new strategies for the synergistic coupling of MXenes and MOFs for future open structured applications.     

A Robust,Freestanding MXene‐Sulfur Conductive Paper for Long‐Lifetime Li–S Batteries

Freestanding, robust electrodes with high capacity and long lifetime are of critical importance to the development of advanced lithium–sulfur (Li–S) batteries for next‐generation electronics, whose potential applications are greatly limited by the lithium polysulfide (LiPS) shuttle effect. Solutions to this issue have mostly focused on the design of cathode hosts with a polar, sulfurphilic, conductive network, or the introduction of an extra layer to suppress LiPS shuttling, which either results in complex fabrication procedures or compromises the mechanical flexibility of the device. A robust Ti₃C₂T_x/S conductive paper combining the excellent conductivity, mechanical strength, and unique chemisorption of LiPSs from MXene nanosheets is reported. Importantly, repeated cycling initiates the in situ formation of a thick sulfate complex layer on the MXene surface, which acts as a protective membrane, effectively suppressing the shuttling of LiPSs and improving the utilization of sulfur. Consequently, the Ti₃C₂T_x/S paper exhibits a high capacity and an ultralow capacity decay rate of 0.014% after 1500 cycles, the lowest value reported for Li–S batteries to date. A robust prototype pouch cell and full cell of Ti₃C₂T_x/S paper // lithium foil and prelithiated germanium are also demonstrated. The preliminary results show that Ti₃C₂T_x/S paper holds great promise for future flexible and wearable electronics.     

MXene-Based Anode-Free Magnesium Metal Battery

Rechargeable magnesium batteries (RMBs) are promising next-generation low-cost and high-energy devices. Among all RMBs, anode-free magnesium metal batteries that use in situ magnesium-plated current collectors as negative electrodes can afford optimal energy densities. However, anode-free magnesium metal batteries have remained elusive so far, as their practical application is plagued by low Mg plating/stripping efficiency due to nonuniform Mg deposition on conventional anode current collectors. Herein, for the first time, an anode-free Mg-metal battery is developed by employing a 3D MXene (Ti₃C₂T_x) film with horizontal Mg electrodeposition. The magnesiophilic oxygen and reactive fluorine terminations in MXene enable an enriched local magnesium-ion concentration and a durable magnesium fluoride-rich solid electrolyte interphase on the Ti₃C₂T_x film surface. Meanwhile, Ti₃C₂T_x MXene exhibits a high lattice geometrical fit with Mg (≈96%) to guide the horizontal electrodeposition of Mg. Consequently, the developed Ti₃C₂T_x film achieves reversible Mg plating/stripping with high Coulombic efficiencies (>99.4%) at high-current-density (5.0 mA cm⁻²) and high-Mg-utilization (50%) conditions. When this Ti₃C₂T_x film is coupled with a pre-magnesized Mo₆S₈ cathode, the anode-free Mg-metal full-cell prototype exhibits a volumetric energy density five times higher than its standard Mg-metal counterpart. This work provides insights into the rational design of anode current collectors to guide horizontal Mg electrodeposition for anode-free Mg metal batteries.     

High Linearity,Low Hysteresis Ti3C2Tx MXene/AgNW/Liquid Metal Self-Healing Strain Sensor Modulated by Dynamic Disulfide and Hydrogen Bonds

Flexible wearable strain sensors have received extensive attention in human–computer interaction, soft robotics, and human health monitoring. Despite significant efforts in developing stretchable electronic materials and structures, developing flexible strain sensors with stable interfaces and low hysteresis remains a challenge. Herein, Ti₃C₂T_x MXene/AgNWs/liquid metal strain sensors (MAL strain sensor) with self-healing function are developed by exploiting the strong interactions between Ti₃C₂T_x MXene/AgNWs/LM and the disulfide and hydrogen bonds inside the self-healing poly(dimethylsiloxane) elastomers. AgNWs lap the Ti₃C₂T_x MXene sheets, and the LM acts as a bridge to increase the lap between Ti₃C₂T_x MXene and AgNWs, thereby improving the interface interaction between them and reducing hysteresis. The MAL strain sensor can simultaneously achieve high sensitivity (gauge factor for up to 3.22), high linearity (R² = 0.98157), a wide range of detection (e.g., 1%–300%), a fast response time (145 ms), excellent repeatability, and stability.In addition, the MAL strain sensor before and after self-healing is combined with a small fish and an electrothermally driven soft robot, respectively, allowing real-time monitoring of the swinging tail of the small fish and the crawling of the soft robot by resistance changes.     

Nonoxidized MXene Quantum Dots Prepared by Microexplosion Method for Cancer Catalytic Therapy

Nanocatalysts based on Fenton or Fenton‐like reactions for amplification of intracellular oxidative stress has become a frontier research area of tumor precise therapy. However, the major translational challenges are low catalytic efficiency, poor biocompatibility, and even potential toxicities. Here, a Ti‐based material with excellent biocompatibility is proposed for cancer treatment. The nonoxidized MXene‐Ti₃C₂T_x quantum dots (NMQDs‐Ti₃C₂T_x) are successfully prepared by a self‐designed microexplosion method. Surprisingly, it has an apparent inhibitory and killing effect on cancer cells, and excellent biocompatibility with normal cells. Moreover, the suppression rate of NMQDs‐Ti₃C₂T_x on xenograft tumor models can reach 91.9% without damaging normal tissues. Mechanistically, the Ti³⁺ of NMQDs‐Ti₃C₂T_x can react with H₂O₂ in the tumor microenvironment and high‐efficiently produce excessive toxic hydroxyl radicals to increase tumor microvascular permeability to synergistically kill cancer cells. This work should pave the way for tumor catalytic therapy applications of Ti‐based material as a promising and safer route.     

Knittable and Washable Multifunctional MXene‐Coated Cellulose Yarns

Textile‐based electronics enable the next generation of wearable devices, which have the potential to transform the architecture of consumer electronics. Highly conductive yarns that can be manufactured using industrial‐scale processing and be washed like everyday yarns are needed to fulfill the promise and rapid growth of the smart textile industry. By coating cellulose yarns with Ti₃C₂T_x MXene, highly conductive and electroactive yarns are produced, which can be knitted into textiles using an industrial knitting machine. It is shown that yarns with MXene loading of ≈77 wt% (≈2.2 mg cm^?1) have conductivity of up to 440 S cm^?1. After washing for 45 cycles at temperatures ranging from 30 to 80 °C, MXene‐coated cotton yarns exhibit a minimal increase in resistance while maintaining constant MXene loading. The MXene‐coated cotton yarn electrode offers a specific capacitance of 759.5 mF cm^?1 at 2 mV s^?1. A fully knitted textile‐based capacitive pressure sensor is also prepared, which offers high sensitivity (gauge factor of ≈6.02), wide sensing range of up to ≈20% compression, and excellent cycling stability (2000 cycles at ≈14% compression strain). This work provides new and practical insights toward the development of platform technology that can integrate MXene in cellulose‐based yarns for textile‐based devices.     

Solar-Driven Interfacial Evaporation Accelerated Electrocatalytic Water Splitting on 2D Perovskite Oxide/MXene Heterostructure

The rational design of economic and high-performance electrocatalytic water-splitting systems is of great significance for energy and environmental sustainability. Developing a sustainable energy conversion-assisted electrocatalytic process provides a promising novel approach to effectively boost its performance. Herein, a self-sustained water-splitting system originated from the heterostructure of perovskite oxide with 2D Ti₃C₂T_x MXene on Ni foam (La_1-xSr_xCoO₃/Ti₃C₂T_x MXene/Ni) that shows high activity for solar-powered water evaporation and simultaneous electrocatalytic water splitting is presented. The all-in-one interfacial electrocatalyst exhibits highly improved oxygen evolution reaction (OER) performance with a low overpotential of 279 mV at 10 mA cm⁻² and a small Tafel slope of 74.3 mV dec⁻¹, superior to previously reported perovskite oxide-based electrocatalysts. Density functional theory calculations reveal that the integration of La_0.9Sr_0.1CoO₃ with Ti₃C₂T_x MXene can lower the energy barrier for the electron transfer and decrease the OER overpotential, while COMSOL simulations unveil that interfacial solar evaporation could induce OH⁻ enrichment near the catalyst surfaces and enhance the convection flow above the catalysts to remove the generated gas, remarkably accelerating the kinetics of electrocatalytic water splitting.     

A Moisture-Driven Actuator Based on Polydopamine-Modified MXene/Bacterial Cellulose Nanofiber Composite Film

As a new 2D material, MXene (Ti₃C₂T_x) shows great potential as a smart multifunctional humidity-responsive actuator due to its high hydrophilicity and conductivity but suffers from ambient oxidation and mechanical brittleness. Inspired by the mussels, the authors overcome these weaknesses by designing and fabricating a nacre-like and lamellar-structured composite film that consists of polydopamine-modified MXene and bacterial cellulose nanofibers, which shows improved properties as a moisture-driven actuator. The actuator has high conductivity (2848 S cm^–1), excellent tensile strength (406 MPa), and toughness (15.3 MJ m^–3). Moreover, the actuator is highly sensitive to moisture with the advantages of fast response (1.6 s), large deformation (176°), and high actuation force output (6.5 N m^–2). It is additionally demonstrated that the actuator works as the electrical switch, robotic arm, and motor in a moisture-driven manner. Overall, it is believed that this work improves the drawbacks of current MXene-based actuators, laying the groundwork for their wider applications as moisture-driven devices.     

High-Performance Ultraviolet Photodetectors Enabled by van der Waals Schottky Junction Based on TiO2 Nanorod Arrays/Au-Modulated Ti3C2Tx MXene

Two-dimensional transition metal carbides and nitrides (MXenes) show tremendous potential for optoelectronic devices due to their excellent electronic properties. Here, a high-performance ultraviolet photodetector based on TiO₂ nanorod arrays/Ti₃C₂T_x MXene van der Waals (vdW) Schottky junction by all-solution process technique is reported. The Ti₃C₂T_x MXene modulated by the Au electrode increases its work function from 4.41 to 5.14 eV to form a hole transport layer. Complemented by the dangling bond-free surface of Ti₃C₂T_x, the Fermi-level pinning effect is suppressed and the electric-field strength of the Schottky junction is enhanced, which promotes charge separation and transport. After applying a bias of −1.5 V, the photovoltaic effect is favorably reinforced, while the hole-trapping mechanism (between TiO₂ and oxygen) and reverse pyroelectric effect are largely eliminated. As a result, the responsivity and specific detectivity of the device with FTO/TiO₂ nanorod arrays/Ti₃C₂T_x/Au structure reach 1.95 × 10⁵ mA W⁻¹ and 4.3 × 10¹³ cm Hz^1/2 W⁻¹ (370 nm, 65 mW cm⁻²), respectively. This work provides an effective approach to enhance the performance of photodetectors by forming the vdW Schottky junction and choosing metal electrodes to modulate MXene as a suitable charge transport layer.     

Surface‐Modified Metallic Ti3C2Tx MXene as Electron Transport Layer for Planar Heterojunction Perovskite Solar Cells

MXenes are a large and rapidly expanding family of 2D materials that, owing to their unique optoelectronic properties and tunable surface termination, find a wide range of applications including energy storage and energy conversion. In this work, Ti₃C₂T_x MXene nanosheets are applied as a novel type of electron transport layer (ETL) in low‐temperature processed planar‐structured perovskite solar cells (PSCs). Interestingly, simple UV‐ozone treatment of the metallic Ti₃C₂T_x that increases the surface Ti? O bonds without any change in its bulk properties such as high electron mobility improves its suitability as an ETL. Improved electron transfer and suppressed recombination at the ETL/perovskite interface results in augmentation of the power conversion efficiency (PCE) from 5.00% in the case of Ti₃C₂T_x without UV‐ozone treatment to the champion PCE of 17.17%, achieved using the Ti₃C₂T_x film after 30 min of UV‐ozone treatment. As the first report on the use of pure MXene layer as an ETL in PSCs, this work shows the great potential of MXenes to be used in PSCs and displays their promise for applications in photovoltaic technology in general.     

Balancing MXene Surface Termination and Interlayer Spacing Enables Superior Microwave Absorption

Surface chemistry and interlayer engineering determines the electrical properties of 2D MXene. However, it remains challenging to regulate the surface and interfacial chemistry of MXene simultaneously. Herein, simultaneous modulation of Ti₃C₂T_x MXene surface termination and layer spacing by alkali treatment are achieved. The electrical and electromagnetic properties of Ti₃C₂T_x are investigated in detail with respect to KOH and ammonia concentration dependence. A high concentration of KOH caused the Ti₃C₂T_x layer spacing to expand to 13.7 Å and the surface O/F ratio to increase to 33.84. Because of its weaker ionization effect, ammonia provides finer tuning compared to the drastic intercalation of KOH with a thorough sweeping of the F-containing groups. Ti₃C₂T_x is enriched with conductive -OH termination after ammonia treatment, which achieves an effective balance with the increased interlayer resistance. Therefore, NH₃H₂O-Ti₃C₂T_x achieves broad-band impedance matching and exhibits an efficient microwave loss of −49.1 dB at a low thickness of 1.7 mm, with an effective frequency bandwidth of 3.9 GHz. The results herein optimize the electrical properties of Ti₃C₂T_x using surface and interfacial chemistry to achieve broad microwave absorption, providing a framework for enhancing the electromagnetic wave loss of intrinsic MXene.     

Constructing Flexible Film Electrode with Porous Layered Structure by MXene/SWCNTs/PANI Ternary Composite for Efficient Low-Grade Thermal Energy Harvest

Thermal energy, constituting the majority of the energy lost through various inefficiencies, is abundant and ubiquitous. With thermogalvanic effect, thermocells (TECs) can directly convert thermal energy into electricity without producing vibration, noise or other waste emissions. This work presents a rational design of flexible film electrodes constructed on a ternary composite of Ti₃C₂T_x MXene (T_x represents surface terminations), polyaniline (PANI) and single-wall carbon nanotubes for TECs, which exhibit notably enhanced thermoelectrochemical performance compared to the widely adopted noble platinum electrodes. The ternary composite electrodes form a porous layered structure with a large electrochemical-active surface area. Experiment and simulation results reveal that synergistic effects of Ti₃C₂T_x and PANI are induced for promoting both mass and charge transport at the electrolyte-electrode interface, resulting in a TEC with an output power of 13.15 µW cm⁻² at the ΔT of 40 K. The TEC also shows a rapid response to the small temperature difference between the human body and the ambient, demonstrating high potential in harvesting low-grade heat to power small electronics.     

Reassembly of MXene Hydrogels into Flexible Films towards Compact and Ultrafast Supercapacitors

The freestanding MXene films are promising for compact energy storage ascribing to their high pseudocapacitance and density, yet the sluggish ion transport caused by the most densely packed structure severely hinders their rate capability. Here, a reassembly strategy for constructing freestanding and flexible MXene-based film electrodes with a tunable porous structure is proposed, where the Ti₃C₂T_x microgels disassembled from 3D structured hydrogel are reassembled together with individual Ti₃C₂T_x nanosheets in different mass ratios to form a densely packed 3D network in microscale and a film morphology in macroscale. The space utilization of produced film can be maximized by a good balance of the density and porosity, resulting in a high volumetric capacitance of 736 F cm⁻³ at an ultrahigh scan rate of 2000 mV s⁻¹. The fabricated supercapacitor yields a superior energy density of 40 Wh L⁻¹ at a power density of 0.83 kW L⁻¹, and an energy density of 21 Wh L⁻¹ can be still maintained even when the power density reaches 41.5 kW L⁻¹, which are the highest values reported to date for symmetric supercapacitors in aqueous electrolytes. More promisingly, the reassembled films can be used as electrodes of flexible supercapacitors, showing excellent flexibility and integrability.     

Large-Area Smooth Conductive Films Enabled by Scalable Slot-Die Coating of Ti3C2Tx MXene Aqueous Inks

Large-area flexible transparent conductive electrodes (TCEs) featuring excellent optoelectronic properties (low sheet resistance, R_s, at high transparency, T) are vital for integration in transparent wearable electronics (i.e., antennas, sensors, supercapacitors, etc.). Solution processing (i.e., printing and coating) of conductive inks yields highly uniform TCEs at low cost, holding great promise for commercially manufacturing of transparent electronics. However, to formulate such conductive inks as well as to realize continuous conductive films in the absence of percolation issue are quite challenging. Herein, the scalable slot-die coating of Ti₃C₂T_x MXene aqueous inks is reported for the first time to yield large-area uniform TCEs with outstanding optoelectronic performance, that is, average DC conductivity of 13 000 ± 500 S cm⁻¹. The conductive MXene nanosheets are forced to orientate horizontally as the inks are passing through the moving slot, leading to the rapid manufacturing of highly aligned MXene TCEs without notorious percolation problems. Moreover, through tuning the ink formulations, such conductive MXene films can be easily adjusted from transparent to opaque as required, demonstrating very low surface roughness and even mirror effects. These high-quality, slot-die-coated MXene TCEs also demonstrate excellent electrochemical charge storage properties when assembled into supercapacitors.     

Mechanisms of the Planar Growth of Lithium Metal Enabled by the 2D Lattice Confinement from a Ti3C2Tx MXene Intermediate Layer

The propensity of Li to form irregular and nonplanar electrodeposits has become a fundamental barrier for fabricating Li metal batteries. Here, a planar, dendrite-free Li metal growth on 2D Ti₃C₂T_x MXene is reported. Ab initio calculations suggest that Li forms a hexagonal close-packed (hcp) layer on the surface of Ti₃C₂T_x via ionic bonding and the lattice confinement. The ionic bonding weakens gradually after a few monolayers, resulting in a nanometers-thin transition region of hcp-Li. Above this transition region, the deposition is dominated by plating of body-centered cubic (bcc) Li via metallic bonding. Formation of a dense and planar Li metal anode with preferential growth along the (110) facet is explained by the lattice matching between Ti₃C₂T_x and hcp-Li and then with bcc-Li, as well as preferred thermodynamic factors including the large dendrite formation energy and small migration barrier for Li. The prepared Li metal anode shows stable cycling in a wide current density range from 0.5 to 10.0 mA cm^–2. The LiFePO₄‖Li full cell fabricated with this Li metal anode exhibits only 9.5% capacity fading after 500 charge–discharge cycles at 1 C rate.