Shuge Dai

To address the limited conductivity and sluggish ion transport of conducting polymer hydrogel electrodes, a MXene/talc/polyaniline/polyvinyl alcohol (MTPP) composite hydrogel was fabricated by one-pot in situ polymerization. Talc provides structural support, while multilayer MXene constructs conductive pathways and regulates the porous architecture. Their synergistic interaction promotes the formation of a three-dimensional porous network, facilitating electrolyte penetration and ion migration. Spectral analysis confirms chemical crosslinking facilitated by ATMP, while functional groups on MXene improve the doping state of polyaniline and charge-transfer kinetics. The optimized MTPP3 electrode delivers an areal specific capacitance of 2498 mF cm-2 at 0.5 mA cm-2. A flexible symmetric supercapacitor assembled with a PVA/H2SO4 gel electrolyte achieves an energy density of 78 μWh cm-2 at a power density of 250 μW cm-2 and retains 92.4% of its capacitance after 5000 charge-discharge cycles.

The MnCo2S4 nanomaterials with five distinct morphologies—rod-like, sheet-like, grass-like, flower-like, and needle-like—on nickel foam (NF) were synthesized via a two-step hydrothermal method. The effects of surfactant types on the resulting morphologies during synthesis were systematically investigated. When evaluated in a three-electrode system, the sheet-like MnCo2S4 exhibited high electrochemical performance (2046 F/g @ 1 A/g) and retained 80.6% of its initial capacitance after 10000 charge/discharge cycles at 10 A/g, indicating its potential for practical supercapacitor applications. Based on these findings, an asymmetric supercapacitor (ASC) was assembled by employing MnCo2S4 nanosheets and activated carbon (AC) as the positive and negative electrode materials, respectively. The device delivered an energy density of 59.3 Wh/kg at a power density of 800 W/kg, alongside superior cycling stability with 81.6% capacitance retention after 10,000 cycles. This work provides insights into the controllable synthesis of electrode materials with specific morphologies.

Flexible supercapacitors utilizing polyaniline (PANI) hydrogels are often limited by the intrinsic structural pulverization of PANI and sluggish ion diffusion within the electrodes. To address these issues, a 1D/2D synergistic network integrated with a molecular anchoring strategy is developed to construct multilayer composite hydrogels. Specifically, multi-walled carbon nanotubes (MWCNTs) and 2D Ti3C2Tx MXene nanosheets are interlocked within a polyvinyl alcohol (PVA) matrix to serve as a conductive scaffold for the in-situ polymerization of PANI. In this architecture, 1D MWCNTs act as physical spacers to prevent the restacking of 2D MXene, thereby maintaining a porous framework and expanding the electrochemically active surface area. Simultaneously, the MXene surface provides abundant molecular anchoring sites for the PANI chains. This structural design not only establishes continuous pathways for electron and ion transport but also effectively accommodates the volumetric swelling and contraction of PANI during continuous charge-discharge processes. As a result, the optimized composite hydrogel delivers an areal specific capacitance of 2337 mF cm-2 at a current density of 1 mA cm-2. Furthermore, the assembled symmetric supercapacitor achieves a maximum energy density of 46.1 μWh cm-2 at a power density of 266.4 μW cm-2. The device also exhibits reliable long-term cycling stability, maintaining 90.3% of its initial capacitance after 8000 cycles. This work provides a practical material design paradigm for constructing structurally stable and electrochemically efficient flexible energy storage devices.

Metal–semiconductor sliding tribovoltaic nanogenerators (MS-TVNGs) represent a promising energy harvesting technology that converts mechanical energy into direct current through dynamic Schottky junction. Although p–n junction-based TVNGs have been investigated in prior studies, metal–semiconductor configurations still lack a complete theoretical foundation. Herin, a comprehensive theoretical model is developed for MS-TVNGs, demonstrating their mechanical-to-electrical energy conversion mechanism due to tribovoltaic effect. The proposed framework unifies semiconductor and circuit principles, which elucidates that synergistic tribovoltaic-contact effects at the interface create electron–hole pairs that are swept by the built-in field to generate current unaffected by sliding direction. Additionally, theoretical results reveal that wide-bandgap semiconductors yield higher voltages, whereas increased doping and generation rates boost current, establishing clear design principles for maximizing power density. COMSOL multi-physics simulations incorporating semiconductor transport, circuit coupling, and moving mesh enable performance optimization through material selection, geometry design, and mechanical excitation. This work provides fundamental principles and practical guidelines for the development of high-efficiency tribovoltaic energy harvesting systems.

Since their birth in 2012, triboelectric nanogenerators (TENGs) have demonstrated astonishing development potential in the fields of energy, sensing, and advanced materials science. The capability of TENGs to convert high-entropy energy into electrical signals has led to technological breakthroughs in multiple domains. In the field of energy harvesting, TENGs have moved beyond conventional fluid energy harvesting, harvesting energy even from slow, low-frequency fluid motion. This has given them significant advantages in distributed energy scenarios. In the field of intelligent sensing, TENG-based sensors have achieved high sensitivity, driving advancements in the industrial Internet of Things and environmental monitoring. High-voltage output (tens of kilovolts) and contact electrification are two characteristics of TENGs. Based on these two characteristics, TENGs can be used to develop new high-voltage power sources and interface probe applications. This topical review introduces the working principles and theoretical foundations of TENGs and then presents four of their cutting-edge applications: fluid energy harvesting, self-adaptive sensors and systems, high-voltage power sources, and interface probes. Finally, the current challenges faced by TENGs in these fields are discussed, and some solutions are offered. This review not only provides a comprehensive overview of the latest applications of TENGs but also offers guidance for their future development.

The pursuit of advanced anode materials to address inferior conductivity and slow ion diffusion has driven the development of fast‐charging sodium‐ion batteries (SIBs). Herein, a promising anode material of KCu ₇ S ₄ nanowires with a tunnel structure is proposed for SIBs. The Na ⁺ (de)insertion mechanisms of the KCu ₇ S ₄ anode are comprehensively elucidated through a combination of in situ TEM/SAED/XRD analyses and theoretical calculations. The detailed intermediates (Na ₃ Cu ₄ S ₄ , NaCuS) and final products (CuS, Cu) during (de)sodiation processes are identified, revealing that the highly mobile Cu ⁺ ion can facilitate the formation of tunnel‐structured Na ₃ Cu ₄ S ₄ and layer‐structured NaCuS during the electrochemical reaction process. The reaction dynamics indicate that the formation of Na ₃ Cu ₄ S ₄ and NaCuS intermediates facilitates electron transfer and ion diffusion during Na ⁺ (de)insertion. Moreover, the KCu ₇ S ₄ anode exhibits a high discharge capacity of 337 mAh g ⁻¹ at 10 A g ⁻¹ , and the corresponding Na ₃ V ₂ (PO ₄ ) ₃ //KCu ₇ S ₄ full cell delivers a high energy density of 303 Wh kg ⁻¹ at 375 W kg ⁻¹ , demonstrating its excellent application prospect. This work opens a new avenue for fast‐charging electrode materials for advanced SIBs.

Tunnel‐structured materials have garnered significant attention as promising candidates for high‐performance rechargeable batteries, owing to their unique structural characteristics that facilitate efficient ionic transport. However, understanding the dynamic processes of ionic transport within these tunnels is crucial for their further development and performance optimization. Analytical in situ transmission electron microscopy (TEM) has demonstrated its effectiveness as a powerful tool for visualizing the complex ionic transport processes in real time. In this review, we summarize the state‐of‐the‐art in situ tracking of ionic transport processes in tunnel‐structured materials for alkali metal‐ion batteries (AMIBs) by TEM observation at the atomic scale, elucidating the fundamental issues pertaining to phase transformations, structural evolution, interfacial reactions and degradation mechanisms. This review covers a wide range of electrode and electrolyte materials used in AMIBs, highlighting the versatility and general applicability of in situ TEM as a powerful tool for elucidating the fundamental mechanisms underlying the performance of AMIBs. Furthermore, this work critically discusses current challenges and future research directions, offering perspectives on the development of next‐generation battery materials through advanced in situ characterization techniques.

Additive manufacturing, commonly known as 3D printing, is an innovative technique for fabricating batteries with arbitrary architectures. Understanding the intricacies of 3D printing designs in sodium battery materials is crucial for optimizing their electrochemical properties and unlocking the full potential of 3D printed sodium batteries. This review provides a comprehensive overview of the key aspects involved in the fabrication of 3D printed sodium batteries, encompassing material selectivity criterion, design considerations, and optimization strategies. Challenges and prospects for the fabrication of high-performance 3D printed sodium batteries are outlined, aiming to provide valuable insights into new conception and theoretical guidance for the design and performance optimization of composites by 3D printing for the practical application of sodium batteries in the future.

Selecting suitable electrode materials for sodium‐ion batteries (SIBs) often relies on the experience gained from lithium‐ion batteries (LIBs), particularly in terms of thermodynamics. However, this approach may fall into a stagnant situation where the development of SIBs consistently lags behind that of LIBs due to the larger ionic radius of Na⁺. Accordingly, it is crucial to establish a dedicated selection rule specifically tailored for SIB electrodes to overcome this challenge. Herein, a screening method is proposed for SIB materials, where an ideal candidate shall form a stable intermediate transition phase with Na⁺. This phase acts as an important bridge that can regulate the insertion/extraction of charge carriers. Atomically resolved transmission electron microscopy demonstrates that KCu₇S₄ can react with Na⁺ to form a stable intermediate phase (Na₃Cu₄S₄). Na₃Cu₄S₄ can undergo reversible conversion reactions, contribute capacity, stabilize the tunnel structure and enhance the migration/diffusion of Na⁺. In contrast, Li⁺ can't form a stable intermediate phase in KCu₇S₄ during lithiation/delithiation, thus losing the ability to effectively regulate Li⁺ insertion/extraction. These findings provide valuable insights for the development of suitable electrode materials for SIBs, emphasizing the importance of stable intermediate phases in regulating charge carrier insertion/extraction and improving overall battery performance.

The effective acquisition of hydrogen energy from the ocean offers a promising sustainable solution for increasing global energy shortage. Herein, a self-powered high-efficient hydrogen generation system is proposed by integrating a triboelectric–electromagnetic hybrid nanogenerator (TEHG), power management circuit (PMC), and an electrolytic cell. Under the wind triggering, as-fabricated TEHG can effectively convert breeze energy into electric energy, which demonstrates a high output current of 20.3 mA at a speed rotation of 700 rpm and the maximal output power of 13.8 mW at a load of 10 MΩ. Remarkably, asdesigned self-powered system can perform a steady and continuous water splitting to produce hydrogen (1.5 µL·min⁻¹) by adding a matching capacitor between the PMC and electrolytic cell. In the circuit, the capacitor can not only function as a charge compensation source for water splitting, but also stabilize the working voltage. Unlike other self-powered water splitting systems, the proposed system does not need catalysts or the complex electrical energy storage/release process, thus improving the hydrogen production efficiency and reducing the cost. This work provides an effective strategy for clean hydrogen energy production and demonstrates the huge potential of the constructed self-powered system toward carbon neutralization.