Abstract Nanocelluloses, as one of the most abundant natural biomass materials on the planet, are conventionally extracted from natural lignocellulosic fibers and present superior combined properties such as high hydrophilicity, low density, high mechanical strength, etc., which show attractive potential as the building blocks to construct different nanocellulose‐based hydrogel membranes for different and even for underwater actuator applications. Notably, the reported nanocellulose‐based hydrogel membranes for underwater actuators driven by osmotic pressure to date exhibit superior uniaxial actuation behaviors. We herein comprehensively summarize the present progress of nanocellulose‐based hydrogel membranes for underwater osmotic actuators, from the building blocks of nanocelluloses to the underwater osmotic actuation (OA) mechanism, including OA, electrochemical OA (ECOA), and corresponding underwater OA applications. Finally, we outline current challenges faced by nanocellulose‐based hydrogel membranes for advanced underwater osmotic actuators, such as ion/water transport kinetics in hydrogel membranes, controllability, and output power density. We also propose corresponding promising strategies for addressing these challenges, including the engineering of the nano‐building blocks, assembly techniques for nanocellulose‐based hydrogel membrane microstructures, programmable actuator configurations, and the integration into remote intelligent actuation systems, aiming to facilitate the high‐quality development of the next generation nanocellulose‐based underwater osmotic actuators.

The development of aqueous aluminum metal batteries is hampered by severe parasitic side reactions at the aluminum metal anode/electrolyte interface. In this work, aluminum-based amorphous alloy anodes are applied to aqueous aluminum metal batteries for the first time. Amorphous aluminum alloys exhibit higher adsorption energy for Al atoms and can regulate the Al3 + deposition potential, thereby offering a kinetic advantage over the hydrogen evolution reaction. Their isotropic deposition behavior suppresses aluminum dendrite growth, while the amorphous structure also improves interfacial chemistry, mitigating anode self-corrosion and passivation. The coupling between the adsorbed atoms and the Al85Ni10Ce5 substrate electrons is stronger, leading to more stable adsorption. Symmetric cells assembled with Al85Ni10Ce5 amorphous alloys demonstrated stable cycling for 5000 h, which present the best cycling performance for bare anode for aqueous aluminum metal batteries at 0.1 mA cm- 2 and 0.1 mAh cm- 2. Moreover, a full cell incorporating this anode with a K2CoFe(CN)6 cathode delivered a high initial discharge capacity of 98.3 mAh g-1. This work provides not only a scalable strategy for high performance aqueous aluminum metal batteries, but also theoretical guidance for the electrode optimization of other metal battery systems.

Aqueous zinc-iodine (Zn-I2) batteries demonstrate promising potential for large-scale energy storage applications. However, the uncontrolled "shuttle effect" of polyiodides (I3 -, I5 -) results in capacity loss, lower Coulombic efficiency (CE), and poor cycling reversibility. Herein, we propose alkyne-rich covalent organic frameworks (COFs) as functional separator coatings to effectively suppress the "shuttle effect", establishing a protective solid electrolyte interphase (SEI) layer to stabilize the Zn metal anode. The effect of different alkyne contents in COFs on the performance of Zn-I2 batteries is investigated, and the results demonstrate that increasing alkyne content significantly improves CE, ion migration rate, and cycling stability. Remarkably, the 100% alkyne-functionalized TAPT-BPTA-COF separator exhibited excellent ion selectivity, effectively blocking the diffusion of polyiodide species, while favoring the transport of Zn2+. This selective transport ensures uniform deposition of Zn2+ on the anode during cycles, thereby reducing internal resistance and improving cycle performance. Notably, the Zn||TAPT-BPTA-COF||I2 battery delivers an initial capacity of 8.4 mAh cm-2 at 20 mA cm-2, retaining 70.1% of the initial capacity over 1200 cycles with 99% CE. Complementary spectroscopic analyses and visualization experiments further confirm that the fully alkyne-conjugated electronic structure of COFs enhances electrical conductivity. This study provides a molecular design strategy for developing high-performance, COF-based electrochemical materials for Zn-I2 battery systems.

Coupled limitations in ionic and thermal transport remain a central challenge for practical solid-state batteries (SSBs), particularly under fast-charging conditions and with high-mass-loading cathodes. Here we introduce a bicontinuous architecture in composite cathodes, achieved through controlled phase separation between an ionic liquid and a polymer matrix. Phase separation is induced by the solvent-dependent solubility difference between polymer and the ionic liquid complex, generating a bicontinuous network that offers continuous pathways for accelerated Li+ transport and efficient thermal dissipation simultaneously. Density functional theory calculations and finite-element simulations reveal that this structure concurrently accelerates lithium-ion transport and facilitates thermal dissipation. This dual enhancement suppresses reaction polarization in thick cathodes, markedly boosting the rate capability of SSBs. A LiNi0.6Co0.2Mn0.2O2 cathode containing 90 wt% active material with a practical loading of 15 mg cm(-2) delivers a specific capacity of 107.7 mAh g(-1) at 5 C and room temperature, over two orders of magnitude higher than conventional homogeneous cathodes. The system further sustains >100 mAh g(-1) across an exceptionally wide temperature window, from -10 degrees C (0.7 C) to 100 degrees C (30 C). At an even higher loading of 25 mg cm(-2), the cell achieves an areal capacity of 3.2 mAh cm(-2) at 1 C (4.5 mA cm(-2)). These findings establish a generalizable design principle for multifunctional cathodes that integrate high energy and power density with robust thermal regulation, advancing the development of next-generation SSBs.

Aqueous zinc-iodine (Zn─I2) batteries are promising candidates for large-scale energy storage owing to their inherent safety, low cost, and high theoretical capacity. However, their practical application is hindered by the polyiodide shuttle effect, sluggish iodine redox kinetics, and uncontrolled zinc dendrite growth. Herein, we design a functional separator modified with metallophthalocyanine-based covalent organic frameworks (MPc-COFs, M═Co, Ni, Cu) to simultaneously regulate iodine electrochemistry and zinc deposition behavior. The optimized Gr@CoPc-COF@GF separator leverages a synergistic mechanism: atomically dispersed Co active sites strongly adsorb polyiodides to suppress shuttling while accelerating iodine redox kinetics, and the well-ordered CoPc-COF nanochannels facilitate uniform Zn2+ flux. As a result, the corresponding Zn─I2 battery delivers a high specific capacity of 208.6 mAh g-1 at 571 mA g-1 and achieves excellent capacity retention with 96.97% Coulombic efficiency after 48 h of open-circuit rest. This work presents a rational separator design strategy for high-performance Zn─I2 batteries, highlighting the importance of molecular-level engineering in advanced energy storage systems.

A physically crosslinked PVA/lignosulfonate hydrogel electrolyte (PLHE) offers high ionic conductivity and mechanical strength for durable seawater-based zinc batteries.

With the rapid development of wearable and portable electronics, flexible micro-energy storage devices are urgently required. Notably, flexible interdigitated zinc-ion micro-capacitors (ZIMCs) have attracted much attention due to their low cost, safety, and high energy storage properties. In terms of the electrode materials for interdigitated ZIMCs, the emerging two-dimensional (2D) materials known as MXenes are ideal candidates due to an MXene’s unique layered structure, ultra-high electronic conductivity, and high charge storage capability. Interdigitated ZIMCs using MXene-based electrodes have already made considerable progress, from their electrochemical mechanisms to their electrode configurations, although some challenges still exist. In this review, we comprehensively summarize current progress in MXene-based interdigitated ZIMCs, including research understanding about the energy storage mechanism, the fabrication techniques for MXene-based electrodes, and their properties for zinc-ion energy storage. We also discuss the existing challenges and offer perspectives on the prospects for MXene-based interdigitated ZIMCs.

ABSTRACT Aqueous zinc‐iodine (Zn‐I 2 ) batteries have emerged as promising candidates for long‐duration energy storage, benefiting from their inherent safety and low cost. However, their practical implementation is hindered by limited cycling stability, primarily caused by polyiodide shuttling and inhomogeneous Zn 2+ flux. Herein, we design a dynamic polymer brush modified separator featuring a pH‐responsive ion‐gating function for bidirectional ion regulation, which is fabricated by grafting polyethyleneimine onto a bacterial cellulose matrix. The brush reversibly adjusts its protonation state and conformation in response to local pH variation, selectively regulating Zn 2+ transport to guide dendrite‐free, (002)‐textured Zn deposition. Simultaneously, the positively charged sites in the brush effectively capture polyiodides during discharge and release them under an electric field upon charging, thereby suppressing the shuttle effect. As a result, the developed separator enables highly stable Zn deposition–stripping over 2300 h at 10 mA cm − 2 and 10 mAh cm − 2 and endows Zn‐I 2 batteries with a cycle life exceeding 64,000 cycles. This work demonstrates a feasible bidirectional ion‐regulation strategy to achieve uniform Zn deposition and inhibit polyiodide shuttling, providing a promising path toward practical and durable aqueous Zn‐I 2 batteries.

ABSTRACT Rechargeable aqueous zinc‐ion batteries offer a cost‐effective and safe solution for large‐scale energy storage. However, uncontrolled Zn dendrite growth, parasitic hydrogen evolution, and poor Zn plating/stripping reversibility still limit their practical deployment. Herein, a Ga‐In liquid metal‐containing hydrogel electrolyte is designed to stabilize the Zn anode. The controlled release of liquid metal regulates the Zn/electrolyte interfacial environment, promotes preferential Zn deposition along the (103) plane, and alleviates structural embrittlement, thereby improving long‐term interfacial stability. Meanwhile, liquid metal released within the hydrogel facilitates the dissolution of Zn dendrites, reducing the risk of internal short circuits. As a result, Zn symmetric cells using the designed hydrogel electrolyte deliver stable cycling for 6000 h at 1 mA cm −2 and 1 mAh cm −2 . Moreover, Zn || NH 4 + ‐V 2 O 5 full cells operate steadily for over 1750 h at 200 mA g −1 with 85% capacity retention. These results demonstrate that a hydrogel electrolyte with controllable liquid metal release provides an effective strategy for stabilizing Zn anodes in aqueous zinc‐ion batteries.

Carbon monoxide (CO) serves as a critical indicator gas for lithium-ion battery thermal runaway, and its selective detection is critical to safeguarding adjacent hydrogen energy infrastructure in integrated electricity-hydrogen systems. This study utilizes first-principles calculations to design a TiS2-doped GeSe (TiS2-GeSe) monolayer for highly selective CO sensing. The TiS2-GeSe composite exhibits stable formation, with a calculated binding energy of -3.13 eV. Doping with TiS2 narrows the band gap of pristine GeSe from 0.735 eV to 0.628 eV through orbital hybridization. The TiS2-GeSe monolayer demonstrates exceptional selectivity for CO, with a more negative adsorption energy (-0.865 eV) than those of CO2, CH4, and H2. Notably, charge transfer analysis reveals that CO acts as an electron donor (ΔQ = +0.023 e) on TiS2-GeSe, opposite to its behavior on pristine GeSe. Furthermore, only CO adsorption introduces new electronic states adjacent to the Fermi level, inducing a notable band gap reduction of 42.1%. Theoretical evaluation predicts a high sensitivity of 158.93 for CO at 303 K, with recovery times decreasing from hundreds of seconds to sub-seconds as temperature increases. This work elucidates the atomic-scale mechanism underlying the enhanced CO selectivity of TiS2-GeSe, providing a theoretical foundation for developing advanced battery safety sensors to protect hydrogen energy infrastructure from risks induced by thermal runaway.

Renewable salinity-gradient osmotic energy can be converted to electric energy by using the reverse electrodialysis (RED) technique, where the ion-exchange membranes (IEMs) play an important role in enhancing the output power for osmotic energy harvesting. To enhance the efficiency of the RED system, numerous advanced membrane materials have been investigated for fabricating high-performance IEMs. In recent years, nanocelluloses with abundant sources, active functional groups, and high-aspect-ratio have emerged as the ideal platform for developing various sustainable, high-performance nanocellulose-based IEMs used in the RED process. The review comprehensively summarized the current research progress of nanocellulose-based IEMs used in the RED process, from the preparation and modification techniques of nanocelluloses, manufacturing processes of nanocellulose-based hybrid/composite IEMs, to their RED performance, such as ion selectivity, output power density, and durability. We also discuss the operational principles of RED from the RED cell, the RED stack, and the property index of the RED process. We finally outline the perspective and challenges for RED-used nanocellulose-based IEMs for the potential practical application of the salinity-gradient osmotic energy conversion.

Biomass, composed of natural polymers such as cellulose, hemicellulose, and lignin, can be converted into circular chemical feedstocks through thermochemical conversion processes like pyrolysis. Char conversion is the rate-limiting step in the thermochemical conversion process, and thus, char reactivity is essential for determining the overall efficiency of pellet-based thermochemical processes. Pyrolysis experiments were conducted on rice straw pellets of different sizes (i.e., 8, 10, and 12 mm) in a vertical quartz tube reactor at 700 °C, and then the chemical structure of chars sampled at different stages and locations within a 10 mm pellet was analyzed using Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). The results indicate that increasing the pellet size facilitates the growth of polycyclic aromatic structures, as evidenced by the observed variations in the abundance of typical aromatic compounds in bio-oil. This also promotes volatile-char interactions, leading to greater deposition of large aromatic structures on the char surface, thereby enhancing char aromatization. Analogous to the spatial scale effect of pellet size on char structure, the evolution of the char structure within a single pellet exhibits distinct spatial heterogeneity during the initial devolatilization and subsequent char aromatization stages due to the location-dependent coupling of heat/mass transfer limitations and aromatization reactions during pyrolysis. Furthermore, the spatiotemporal evolution of the char structure leads to differences in the specific reactivity: during the devolatilization stage at 75 s, the center exhibits the highest reactivity, whereas the outer surface becomes the most reactive in the subsequent char aromatization stage at 300 s.

The charge gradient separator facilitates Zn 2+ diffusion and simultaneously restricts SO 4 2− from approaching the Zn anode surface, thus effectively promoting uniform Zn deposition and suppressing side reactions.

The high-reversibility conversion of four-electron zinc-iodine (Zn-I2) batteries is hindered by the rapid hydrolysis of I+ intermediates. Natural seawater (NS), as a low-chloride ion (Cl-) medium, holds potential for stabilizing I+. However, commercial glass fiber separators struggle to construct the required high-Cl- microenvironment at the I2 cathode interface due to their large pores and strong hydrophilicity. Here, we develop a scalable separator with a charge gradient and fine-tuned wettability, working synergistically with a NS-based electrolyte to resolve the above issues through regulation of the electrode interfacial microenvironment. The asymmetric charge drives the enrichment of Cl- at the I2 cathode interface, forming a localized high Cl- microenvironment to stabilize I+. Meanwhile, the fine-tuned wettability reduces interfacial water activity, thereby suppressing I+ hydrolysis. Consequently, the Zn||I2 full cell exhibits a minimal capacity decay rate of only 0.0013% per cycle after 50 000 cycles at 10 A g–1 and maintains stable cycling under harsh conditions, including a low N/P (∼2.5), or at low temperatures (-20 °C). Furthermore, the assembled Ah-level pouch cell (∼1.3 Ah) operates stably for over 450 cycles. This work provides a new strategy for realizing high-performance, low-cost four-electron Zn-I2 batteries.

Aqueous aluminum metal batteries (AAMBs) are attractive candidates for large-scale energy storage due to their high safety, the natural abundance of aluminum, and low cost. However, the rapid passivation of the aluminum anode and parasitic side reactions with the electrolyte, such as hydrogen evolution, hinder cycling stability and practical energy density, presenting key challenges for current research. Here, we report an amorphous Al-Ni-La alloy as the anode for aqueous aluminum-metal batteries. Benefiting from its unique atomic-scale disordered structure and metastable nature, the amorphous alloy significantly reduces the nucleation energy barrier for aluminum deposition, thereby enabling uniform Al-ion plating behavior. Theoretical calculations reveal that the amorphous alloy exhibits stronger adsorption toward aluminum ions than crystalline aluminum, with a-Al90Ni6La4 showing the highest adsorption energy among the studied compositions. Analysis of the projected density of states (PDOS) of adsorbed Al atoms revealed that the Al-Ni-La amorphous alloy surface exhibits stronger electronic state hybridization near the Fermi level, thereby significantly enhancing the adsorption stability of the Al coating. As a result, the presence of the amorphous structure effectively facilitates aluminum deposition and enhances interfacial ion transport. The symmetric cell assembled with an aluminum amorphous alloy electrode demonstrated stable operation for over 6000 h, which represents the longest cycling life reported to date for an unmodified aqueous aluminum metal anode at 0.1 mAh cm-2. When paired with a K2CoFe(CN)6 cathode, full cells retain a capacity of 43.5 mAh g-1 after 200 cycles. Amorphous alloys are employed for the first time as anodes in aqueous aluminum-metal batteries, offering new insights and directions for designing highperformance aqueous aluminum batteries.

Polyethylene oxide (PEO)-based solid-state polymer electrolytes (SPEs) are promising key materials for all-solid-state lithium metal batteries because of their good processability and compatibility with Li metal. However, their practical deployment is limited by the low Li+ conductivity, which mainly originates from the high migration energy barrier induced by strong Li-polymer coordination. Here, this work proposes a coordination-entropy-increase driven all-solid-state electrolyte, PEO-LiTFSI-MgCl2-AlCl3-ZrCl4 (SPE-MAZ). The introduction of multi-cations induces diverse coordination structures on PEO chains, creating Li+ sites with varied binding strengths and distinct energy barriers. These features narrow the energy differences between adjacent sites, facilitate Li+ mobility, and achieve enhanced ionic conduction. SPE-MAZ delivers an ionic conductivity of 0.103 mS cm-1 at room temperature (RT, 30 °C). The assembled Li/SPE-MAZ/Li symmetric cells maintain stable operation for over 1700 h at 60 °C. The LiFePO4/SPE-MAZ/Li full cells achieve a specific capacity of 115.1 mAh g-1 at 60 °C and 5 C, with 80% capacity retention preserved after 100 cycles at RT and 0.1 C. This coordination-entropy-increase strategy leads to the realization of SPEs featuring both high conductivity and good stability, offering a novel perspective for SPEs design.

The development of separator by tunning the zincophilic and iodide ion-repulsive properties of covalent organic frameworks (COFs) that regulate cycle lifespan and capacity of aqueous zinc-iodine (Zn-I2) batteries is one of challenges. In this work, we have shown a systematic strategic-driven investigation to elucidate the role of functional triazine properties in COF modified separator towards overall performance of aqueous Zn-I2 batteries. As such, three COFs with the same topology but different triazine number in their structures, have been synthesized, among which the triazine-richest framework, TAPA-TTB-COF-based separator demonstrated to be most effective to guide uniform Zn2+ flux and simultaneously inhibit polyiodide shuttling due to the zincophilic nature and good iodide ion-repulsive capability of triazine. Consequently, the Zn||Gr@TAPA-TTB-COF@GF||Zn symmetric battery achieves a long life of more than 2100 h (5.0 mA cm-2) and the initial area capacity of the Zn||Gr@TAPA-TTB-COF@GF||I2 battery reaches up to 5.5 mAh cm-2 (20 mA cm-2). After 2000 cycles, the discharge capacity can still maintain at3.0 mAh cm-2 with a capacity decay rate of only 0.023 % per cycle. This study provides guidance for the rational design of functional COFs separators and promotes their application in high energy storage systems.