Inkjet-printed flexible V2CTx film electrodes with excellent photoelectric properties and high capacities for energy storage device.

Energy storage devices are progressively advancing in the light-weight, flexible, and wearable direction. Ti3C2Tx flexible film electrodes fabricated via a non-contact, cost-effective, high-efficiency, and large-scale inkjet printing technology were capable of satisfying these demands in our previous report. However, other MXenes that can be employed in flexible energy storage devices remain undiscovered. Herein, flexible V2CTx film electrodes (with the low formula weight vs Ti3C2Tx film electrodes) with both high capacities and excellent photoelectric properties were first fabricated. The area capacitances of V2CTx film electrodes reached 531.3-5787.0 µF⋅cm-2 at 5 mV⋅s-1, corresponding to the figure of merits (FoMs) of 0.07-0.15. Noteworthy, V2CTx film electrode exhibited excellent cyclic stability with the capacitance retention of 83 % after 7,000 consecutive charge-discharge cycles. Furthermore, flexible all solid-state symmetric V2CTx supercapacitor was assembled with the area capacitance of 23.4 µF⋅cm-2 at 5 mV⋅s-1. Inkjet printing technology reaches the combination of excellent photoelectric properties and high capacities of flexible V2CTx film electrodes, which provides a new strategy for manufacturing MXene film electrodes, broadening the application prospect of flexible energy storage devices.

Microporous tungsten oxide spheres coupled with Ti3C2Txnanosheets for high-volumetric capacitance supercapacitors.

In the contemporary landscape of technological advancements, the burgeoning demand for portable electronics and flexible wearable devices has necessitated the development of energy storage systems with superior volumetric performance. Tungsten oxide (WO3), known for its high density and theoretical capacitance, is a promising electrode material for supercapacitors. However, low conductivity and poor cycling stability are still the key bottlenecks for its application. Herein, a novel composite comprising hollow porous WO3 spheres (HPWS) derived by template method was electrostatic self-assembled on the surface of the Ti3C2Tx nanosheets. The resulting electrodes exhibited ultra-high volumetric capacitance of 1930 F cm-3 at 1 A g-1 and rate capability of 46% at 50 A g-1, attributed to enhanced ion accessibility from microporous structure and electron transport from conductive network of Ti3C2Tx even at a high packing density of 3.86 g cm-3. Utilizing HPWS/Ti3C2Tx as the negative electrode and porous carbon as the positive electrode, the assembled asymmetric supercapacitor achieved an energy density of 31 Wh kg-1 at a power density of 650 W kg-1 with over 107% capacitance retention after 5000 cycles. This work provides a promising approach for developing next-generation supercapacitors with ultra-high volumetric capacitance.

Regulating the Porosity and Bipolarity of Polyimide-Based Covalent Organic Framework for Advanced Aqueous Dual-Ion Symmetric Batteries.

The all-organic aqueous dual-ion batteries (ADIBs) have attracted increasing attention due to the low cost and high safety. However, the solubility and unstable activity of organic electrodes restrict the synergistic storage of anions and cations in the symmetric ADIBs. Herein, a novel polyimide-based covalent organic framework (labeled as NTPI-COF) is constructed, featured with the boosted structure stability and electronic conductivity. Through regulating the porosity and bipolarity integrally, the NTPI-COF possesses hierarchical porous structure (mesopore and micropore) and abundant bipolar active centers (C═O and C─N), which exhibits rapid dual-ion transport and storage effects. As a result, the NTPI-COF as the electrodes for ADIBs deliver a high reversible capacity of 109.7 mA h g-1 for Na+ storage and that of 74.8 mA h g-1 for Cl- storage at 1 A g-1, respectively, and with a capacity retention of 93.2% over 10 000 cycles at 10 A g-1. Additionally, the all-organic ADIBs with symmetric NTPI-COF electrodes achieve an impressive energy density of up to 148 W h kg-1 and a high power density of 2600 W kg-1. Coupling the bipolarity and porosity of the all-organic electrodes applied in ADIBs will further advance the development of low-cost and large-scale energy storage.

Planar Deposition via In Situ Conversion Engineering for Dendrite-Free Zinc Batteries.

Owing to the considerable capacity, high safety, and abundant zinc resources, zinc-ion batteries (ZIBs) have been garnering much attention. Nonetheless, the unsatisfactory cyclic lifespan and poor reversibility originate from side reactions and dendrite obstacles to their practical applications. In addition to inhibiting the corrosion of aqueous electrolytes, regulating planar deposition is a key strategy to enhance their long-term stability. Herein, an in situ conversion strategy is reported to construct a protective "dual-layer" structure (VZSe/V@Zn) on zinc metal, consisting of the VSe2-ZnSe outer layer with low lattice mismatch to Zn (002) plane, and corrosion-resistant nanometallic V inner layer. Such design integrates superior interfacial ionic/electronic transfer, corrosion resistance, and unique planar deposition regulation capability. The as-prepared VZSe/V@Zn demonstrates remarkable durability of 238 h at 50 mA cm-2 with a high depth of discharge (68.3% DOD) in the Zn||Zn symmetric cell. Even in the anode-free system, the as-prepared protective layer can extend the cycle life up to 2000 cycles, with an outstanding capacity retention of 93.1% and ultra-high average coulombic efficiency of 99.998%. This work delineates an effective strategy for fabricating lattice-matching protective layers, with profound implications for elucidating zinc deposition mechanisms and paving the way for the development of high-performance zinc batteries.

Precisely Constructing Orbital-Coupled Fe─Co Dual-atom Sites for High-Energy-Efficiency Zn-Air/Iodide Hybrid Batteries.

Rechargeable Zn-air batteries (ZABs) are promising for energy storage and conversion. However, the high charging voltage and low energy efficiency hinder their commercialization. Herein, these challenges are addressed by employing precisely constructed multifunctional Fe-Co diatomic site catalysts (FeCo-DACs) and integrating iodide/iodate redox into ZABs to create Zinc-air/iodide hybrid batteries (ZAIHBs) with highly efficient multifunctional catalyst. The strong coupling between the 3d orbitals of Fe and Co weakens the excessively strong binding strength between active sites and intermediates, enhancing the catalytic activities for oxygen reduction/evolution reaction and iodide/iodate redox. Consequently, FeCo-DACs exhibit outstanding bifunctional oxygen catalytic activity with a small potential gap (ΔE = 0.66 V) and outstanding stability. Moreover, an outstanding catalytic performance toward iodide/iodate redox is obtained. Therefore, FeCo-DAC-based ZAIHBs exhibit high energy efficiency of up to 75% at 10 mA cm-2 and excellent cycling stability (72% after 500 h). This research offers critical insights into the rational design of DACs and paves the way for high-energy efficiency energy storage devices.

Potential Gradient-Driven Dual-Functional Electrochromic and Electrochemical Device Based on a Shared Electrode Design.

The integration of electrochromic devices and energy storage systems in wearable electronics is highly desirable yet challenging, because self-powered electrochromic devices often require an open system design for continuous replenishment of the strong oxidants to enable the coloring/bleaching processes. A self-powered electrochromic device has been developed with a close configuration by integrating a Zn/MnO2 ionic battery into the Prussian blue (PB)-based electrochromic system. Zn and MnO2 electrodes, as dual shared electrodes, the former one can reduce the PB electrode to the Prussian white (PW) electrode and serves as the anode in the battery; the latter electrode can oxidize the PW electrode to its initial state and acts as the cathode in the battery. The bleaching/coloring processes are driven by the gradient potential between Zn/PB and PW/MnO2 electrodes. The as-prepared Zn||PB||MnO2 system demonstrates superior electrochromic performance, including excellent optical contrast (80.6%), fast self-bleaching/coloring speed (2.0/3.2 s for bleaching/coloring), and long-term self-powered electrochromic cycles. An air-working Zn||PB||MnO2 device is also developed with a 70.3% optical contrast, fast switching speed (2.2/4.8 s for bleaching/coloring), and over 80 self-bleaching/coloring cycles. Furthermore, the closed nature enables the fabrication of various flexible electrochromic devices, exhibiting great potentials for the next-generation wearable electrochromic devices.

A Biomimetic Cement-Based Solid-State Electrolyte with Both High Strength and Ionic Conductivity for Self-Energy-Storage Buildings.

Cement-based materials are the foundation of modern buildings but suffer from intensive energy consumption. Utilizing cement-based materials for efficient energy storage is one of the most promising strategies for realizing zero-energy buildings. However, cement-based materials encounter challenges in achieving excellent electrochemical performance without compromising mechanical properties. Here, we introduce a biomimetic cement-based solid-state electrolyte (labeled as l-CPSSE) with artificially organized layered microstructures by proposing an in situ ice-templating strategy upon the cement hydration, in which the layered micropores are further filled with fast-ion-conducting hydrogels and serve as ion diffusion highways. With these merits, the obtained l-CPSSE not only presents marked specific bending and compressive strength (2.2 and 1.2 times that of traditional cement, respectively) but also exhibits excellent ionic conductivity (27.8 mS·cm-1), overwhelming most previously reported cement-based and hydrogel-based electrolytes. As a proof-of-concept demonstration, we assemble the l-CPSSE electrolytes with cement-based electrodes to achieve all-cement-based solid-state energy storage devices, delivering an outstanding full-cell specific capacity of 72.2 mF·cm-2. More importantly, a 5 × 5 cm2 sized building model is successfully fabricated and operated by connecting 4 l-CPSSE-based full cells in series, showcasing its great potential in self-energy-storage buildings. This work provides a general methodology for preparing revolutionary cement-based electrolytes and may pave the way for achieving zero-carbon buildings.

Ultrathin, Mechanically Durable, and Scalable Polymer-in-Salt Solid Electrolyte for High-Rate Lithium Metal Batteries.

Polymer-in-salt solid-state electrolytes (PIS SSEs) are emerging for high room-temperature ionic conductivity and facile handling, but suffer from poor mechanical durability and large thickness. Here, Al2O3-coated PE (PE/AO) separators are proposed as robust and large-scale substrates to trim the thickness of PIS SSEs without compromising mechanical durability. Various characterizations unravel that introducing Al2O3 coating on PE separators efficiently improves the wettability, thermal stability, and Li-dendrite resistance of PIS SSEs. The resulting PE/AO@PIS demonstrates ultra-small thickness (25 µm), exceptional mechanical durability (55.1 MPa), high decomposition temperature (330 °C), and favorable ionic conductivity (0.12 mS cm-1 at 25 °C). Consequently, the symmetrical Li cells remain stable at 0.1 mA cm-2 for 3000 h, without Li dendrite formation. Besides, the LiFePO4|Li full cells showcase excellent rate capability (131.0 mAh g-1 at 10C) and cyclability (93.6% capacity retention at 2C after 400 cycles), and high-mass-loading performance (7.5 mg cm-2). Moreover, the PE/AO@PIS can also pair with nickel-rich layered oxides (NCM811 and NCM9055), showing a remarkable specific capacity of 165.3 and 175.4 mAh g-1 at 0.2C after 100 cycles, respectively. This work presents an effective large-scale preparation approach for mechanically durable and ultrathin PIS SSEs, driving their practical applications for next-generation solid-state Li-metal batteries.

Stabilizing Solid Electrolyte Interphase on Liquid Metal Via Dynamic Hydrogel-Derived Carbon Framework Encapsulation.

Eutectic gallium-indium liquid metal (EGaIn-LM), with a considerable capacity and unique self-healing properties derived from its intrinsic liquid nature, gains tremendous attention for lithium-ion batteries (LIBs) anode. However, the fluidity of the LM can trigger continuous consumption of the electrolyte, and its liquid-solid transition during the lithiation/de-lithiation process may result in the rupture of the solid electrolyte interface (SEI). Herein, LM is employed as an initiator to in situ assemble the 3D hydrogel for dynamically encapsulating itself; the LM nanoparticles can be homogeneously confined within the hydrogel-derived carbon framework (HDC) after calcination. Such design effectively alleviates the volume expansion of LM and facilitates electron transportation, resulting in a superior rate capability and long-term cyclability. Further, the "dual-layer" SEI structure and its key components, including the robust LiF outer layer and corrosion-resistant and ionic conductive LiGaOx inner layer are revealed, confirming the involvement of LM in the formation of SEI, as well as the important role of carbon framework in reducing interfacial side reactions and SEI decomposition. This work provides a distinct perspective for the formation, structural evolution, and composition of SEI at the liquid/solid interface, and demonstrates an effective strategy to construct a reliable matrix for stabilizing the SEI.

An acetate electrolyte for enhanced pseudocapacitve capacity in aqueous ammonium ion batteries.

Ammonium ion batteries are promising for energy storage with the merits of low cost, inherent security, environmental friendliness, and excellent electrochemical properties. Unfortunately, the lack of anode materials restricts their development. Herein, we utilized density functional theory calculations to explore the V2CTx MXene as a promising anode with a low working potential. V2CTx MXene demonstrates pseudocapacitive behavior for ammonium ion storage, delivering a high specific capacity of 115.9 mAh g-1 at 1 A g-1 and excellent capacity retention of 100% after 5000 cycles at 5 A g-1. In-situ electrochemical quartz crystal microbalance measurement verifies a two-step electrochemical process of this unique pseudocapacitive storage behavior in the ammonium acetate electrolyte. Theoretical simulation reveals reversible electron transfer reactions with [NH4+(HAc)3]···O coordination bonds, resulting in a superior ammonium ion storage capacity. The generality of this acetate ion enhancement effect is also confirmed in the MoS2-based ammonium-ion battery system. These findings open a new door to realizing high capacity on ammonium ion storage through acetate ion enhancement, breaking the capacity limitations of both Faradaic and non-Faradaic energy storage.

Highly Stable Photo-Assisted Zinc-Ion Batteries via Regulated Photo-Induced Proton Transfer.

Photo-assisted ion batteries utilize light to boost capacity but face cycling instability due to complex charge/ion transfer under illumination. This study identified photo-induced proton transfer (photo-induced PT) as a significant process in photo-(dis)charging of widely-used V2O5-based zinc-ion batteries, contributing to enhanced capacity under illumination but jeopardizing photo-stability. Photo-induced PT occurs at 100 ps after photo-excitation, inducing rapid proton extraction into V2O5 photoelectrode. This process creates a proton-deficient microenvironment on surface, leading to repetitive cathode dissolution and anode corrosion in each cycle. Enabling the intercalated protons from photo-induced PT to be reversibly employed in charge-discharge processes via the anode-alloying strategy achieves high photo-stability for the battery. Consequently, a ~54 % capacity enhancement was achieved in a V2O5-based zinc-ion battery under illumination, with ~90 % capacity retention after 4000 cycles. This extends the photo-stability record by 10 times. This study offers promising advancements in energy storage by addressing instability issues in photo-assisted ion batteries.

Sn Whiskers from Ti2 SnC Max Phase: Bridging Dual-Functionality in Electromagnetic Attenuation.

In the ever-evolving landscape of complex electromagnetic (EM) environments, the demand for EM-attenuating materials with multiple functionalities has grown. 1D metals, known for their high conductivity and ability to form networks that facilitate electron migration, stand out as promising candidates for EM attenuation. Presently, they find primary use in electromagnetic interference (EMI) shielding, but achieving a dual-purpose application for EMI shielding and microwave absorption (MA) remains a challenge. In this context, Sn whiskers derived from the Ti2 SnC MAX phase exhibit exceptional EMI shielding and MA properties. A minimum reflection loss of -44.82 dB is achievable at lower loading ratios, while higher loading ratios yield efficient EMI shielding effectiveness of 42.78 dB. These qualities result from a delicate balance between impedance matching and EM energy attenuation via adjustable conductive networks; and the enhanced interfacial polarization effect at the cylindrical heterogeneous interface between Sn and SnO2 , visually characterized through off-axis electron holography, also contributes to the impressive performance. Considering the compositional diversity of MAX phases and the scalable fabrication approach with environmental friendliness, this study provides a valuable pathway to multifunctional EM attenuating materials based on 1D metals.

Simultaneous derivatization and exfoliation of a multilayered Ti3C2Tx MXene into amorphous TiO2 nanosheets for stable K-ion storage.

Two-dimensional transition metal compounds (2D TMCs) have been widely reported in the fields of energy storage and conversion, especially in metal-ion storage. However, most of them are crystalline and lack active sites, and this brings about sluggish ion storage kinetics. In addition, TMCs are generally nonconductors or semiconductors, impeding fast electron transfer at high rates. Herein, we propose a facile one-step route to synthesize amorphous 2D TiO2 with a carbon coating (a-2D-TiO2@C) by simultaneous derivatization and exfoliation of a multilayered Ti3C2Tx MXene. The amorphous structure endows 2D TiO2 with abundant active sites for fast ion adsorption and diffusion, while the carbon coating can facilitate electron transport in an electrode. Owing to these intriguing structural and compositional synergies, a-2D-TiO2@C delivers good cycling stability with a long-term capacity retention of 86% after 2000 cycles at 1.0 A g-1 in K-ion storage. When paired with Prussian blue (KPB) cathodes, it exhibits a high full-cell capacity of 50.8 mA h g-1 at 100 mA g-1 after 140 cycles, which demonstrates its great potential in practical applications. This contribution exploits a new approach for the facile synthesis of a-2D-TMCs and their broad applications in energy storage and conversion.

Robust and Flame-Retardant Zylon Aerogel Fibers for Wearable Thermal Insulation and Sensing in Harsh Environment.

The exceptional lightweight, highly porous, and insulating properties of aerogel fibers make them ideal for thermal insulation. However, current aerogel fibers face limitations due to their low resistance to harsh environments and a lack of intelligent responses. Herein, a universal strategy for creating polymer aerogel fibers using crosslinked nanofiber building blocks is proposed. This approach combines controlled proton absorption gelation spinning with a heat-induced crosslinking process. As a proof-of-concept, Zylon aerogel fibers that exhibited robust thermal stability (up to 650 °C), high flame retardancy (limiting oxygen index of 54.2%), and extreme chemical resistance are designed and synthesized. These fibers possess high porosity (98.6%), high breaking strength (8.6 MPa), and low thermal conductivity (0.036 W m-1 K-1 ). These aerogel fibers can be knotted or woven into textiles, utilized in harsh environments (-196-400 °C), and demonstrate sensitive self-powered sensing capabilities. This method of developing aerogel fibers expands the applications of high-performance polymer fibers and holds great potential for future applications in wearable smart protective fabrics.

Built-In Electric Field-Driven Ultrahigh-Rate K-Ion Storage via Heterostructure Engineering of Dual Tellurides Integrated with Ti3C2Tx MXene.

Exploiting high-rate anode materials with fast K+ diffusion is intriguing for the development of advanced potassium-ion batteries (KIBs) but remains unrealized. Here, heterostructure engineering is proposed to construct the dual transition metal tellurides (CoTe2/ZnTe), which are anchored onto two-dimensional (2D) Ti3C2Tx MXene nanosheets. Various theoretical modeling and experimental findings reveal that heterostructure engineering can regulate the electronic structures of CoTe2/ZnTe interfaces, improving K+ diffusion and adsorption. In addition, the different work functions between CoTe2/ZnTe induce a robust built-in electric field at the CoTe2/ZnTe interface, providing a strong driving force to facilitate charge transport. Moreover, the conductive and elastic Ti3C2Tx can effectively promote electrode conductivity and alleviate the volume change of CoTe2/ZnTe heterostructures upon cycling. Owing to these merits, the resulting CoTe2/ZnTe/Ti3C2Tx (CZT) exhibit excellent rate capability (137.0 mAh g-1 at 10 A g-1) and cycling stability (175.3 mAh g-1 after 4000 cycles at 3.0 A g-1, with a high capacity retention of 89.4%). More impressively, the CZT-based full cells demonstrate high energy density (220.2 Wh kg-1) and power density (837.2 W kg-1). This work provides a general and effective strategy by integrating heterostructure engineering and 2D material nanocompositing for designing advanced high-rate anode materials for next-generation KIBs.

Realizing Unassisted Photo-Charging of Zinc-Air Batteries by Anisotropic Charge Separation in Photoelectrodes.

Solar rechargeable zinc-air battery is a promising approach for capturing and storing intermittent solar energy through photoelectrochemical reactions. However, unassisted photo-charging of zinc-air batteries is challenging due to suboptimal carrier accumulation on photoelectrodes, resulting in sluggish reaction kinetics. Here, unassisted photo-charging of zinc-air battery is achieved by investigating anisotropic photogenerated charge separation on a series of representative semiconductors (ZnIn2 S4 , TiO2 , and In2 O3 ), among which the exceptional anisotropic charge separation on a ZnIn2 S4 photoelectrode is revealed based on anisotropic charge diffusion capabilities. The charge separation is facet-dependent, which is observed using Kelvin probe force microscopy, verifying a cause-and-effect relationship between the photo-charge accumulation on photoelectrodes and their photo-charging performance in zinc-air batteries. This work achieves an unassisted photo-charging current density of 1.9 mA cm-2 with a light-to-chemical energy conversion efficiency of 1.45%, highlighting the importance of anisotropic semiconductors for unassisted photo-charging of zinc-air batteries via efficient photogenerated charge separation.

Multifunctional MXene/C Aerogels for Enhanced Microwave Absorption and Thermal Insulation.

Two-dimensional transition metal carbides and nitrides (MXene) have emerged as promising candidates for microwave absorption (MA) materials. However, they also have some drawbacks, such as poor impedance matching, high self-stacking tendency, and high density. To tackle these challenges, MXene nanosheets were incorporated into polyacrylonitrile (PAN) nanofibers and subsequently assembled into a three-dimensional (3D) network structure through PAN carbonization, yielding MXene/C aerogels. The 3D network effectively extends the path of microcurrent transmission, leading to enhanced conductive loss of electromagnetic (EM) waves. Moreover, the aerogel's rich pore structure significantly improves the impedance matching while effectively reducing the density of the MXene-based absorbers. EM parameter analysis shows that the MXene/C aerogels exhibit a minimum reflection loss (RLmin) value of - 53.02 dB (f = 4.44 GHz, t = 3.8 mm), and an effective absorption bandwidth (EAB) of 5.3 GHz (t = 2.4 mm, 7.44-12.72 GHz). Radar cross-sectional (RCS) simulations were employed to assess the radar stealth effect of the aerogels, revealing that the maximum RCS reduction value of the perfect electric conductor covered by the MXene/C aerogel reaches 12.02 dB m2. In addition to the MA performance, the MXene/C aerogel also demonstrates good thermal insulation performance, and a 5-mm-thick aerogel can generate a temperature gradient of over 30 °C at 82 °C. This study provides a feasible design approach for creating lightweight, efficient, and multifunctional MXene-based MA materials.

Single-Ion-Conducting Hydrogel Electrolytes Based on Slide-Ring Pseudo-Polyrotaxane for Ultralong-Cycling Flexible Zinc-Ion Batteries.

Flexible zinc-ion batteries (ZIBs) with high capacity and long cycle stability are essential for wearable electronic devices. Hydrogel electrolytes have been developed to provide ion-transfer channels while maintaining the integrity of ZIBs under mechanical strain. However, hydrogel matrices are typically swollen with aqueous salt solutions to increase ionic conductivity, which can hinder intimate contact with electrodes and reduce mechanical properties. To address this, a single-Zn-ion-conducting hydrogel electrolyte (SIHE) is developed by integrating polyacrylamide network and pseudo-polyrotaxane structure. The SIHE exhibits a high Zn2+ transference number of 0.923 and a high ionic conductivity of 22.4 mS cm-1 at room temperature. Symmetric batteries with SIHE demonstrate stable Zn plating/stripping performance for over 160 h, with a homogenous and smooth Zn deposition layer. Full cells with La-V2 O5 cathodes exhibit a high capacity of 439 mA h g-1 at 0.1 A g-1 and excellent capacity retention of 90.2% after 3500 cycles at 5 A g-1 . Moreover, the flexible ZIBs display stable electrochemical performance under harsh conditions, such as bending, cutting, puncturing, and soaking. This work provides a simple design strategy for single-ion-conducting hydrogel electrolytes, which could pave the way for long-life aqueous batteries.

Novel 2D/2D 1T-MoS2/Ti3C2Tz heterostructures for high-voltage symmetric supercapacitors.

Electrode materials play a crucial role in the electrochemical performance of supercapacitors (SCs). In recent years, 1T-MoS2 and MXene have been extensively studied as potential electrode materials. However, 1T-MoS2 suffers from the metastable property, rigorous synthesis process, and nanosheet restacking issue, while the specific capacitance of MXene is restricted, limiting their supercapacitor performance. To fully exploit the advantages of both materials and address their respective problems, 1T-MoS2/Ti3C2Tz 2D/2D heterostructures are synthesized through a simple hydrothermal method. The existence of heterojunctions is confirmed by XPS and TEM. The different ratios between MoS2 and Ti3C2Tz are investigated, and the electrochemical test is carried out in a "water-in-salt" electrolyte (20 mol kg-1 LiCl). The results demonstrate that the heterostructures exhibit enhanced electrochemical performance. The optimized ratio of 1T-MoS2/Ti3C2Tz is 2 : 1, and the specific capacitance reaches 250 F g-1 at 1 A g-1 with a wide potential window of -0.9 to 0.5 V vs. Ag/AgCl. The capacitance retention is 82.3% (at 10 A g-1) after 5000 cycles, and the average coulombic efficiency (ACE) was 99.96%. Assembled into symmetric SCs (SSCs), the energy density of 12.0 W h kg-1 at a power density of 139.9 W kg-1 is achieved with a high voltage of 1.4 V. It also has 82.6% capacitance retention and 99.95% ACE after 5000 cycles at 5 A g-1. This work is expected to stimulate novel research towards the wide application of 2D/2D heterostructures in SCs.

In-Situ Growth of ZnO Whiskers on Ti2ZnC MAX Phases.

ZnO whiskers have many applications, such as in medical and photocatalysis fields. In this study, an unconventional preparation approach is reported, realizing the in-situ growth of ZnO whiskers on Ti2ZnC. The weak bonding between the layer of Ti6C-octahedron and the Zn-atom layers leads to the easy extraction of Zn atoms from Ti2ZnC lattice points, resulting in the formation of ZnO whiskers on the Ti2ZnC surface. This is the first time that ZnO whiskers have been found to grow in-situ on Ti2ZnC substrate. Further, this phenomenon is amplified when the size of the Ti2ZnC grains is mechanically reduced by ball-milling, which bodes a promising route to prepare ZnO in-situ on a large scale. Additionally, this finding can also help us better understand the stability of Ti2ZnC and the whiskering mechanism of MAX phases.