Covalent organic frameworks (COFs), which are constructed by linking organic building blocks via dynamic covalent bonds, are newly emerged and burgeoning crystalline porous copolymers with features including programmable topological architecture, pre-designable periodic skeleton, well-defined micro-/meso-pore, large specific surface area, and customizable electroactive functionality. Those benefits make COFs as promising candidates for advanced electrochemical energy storage. Especially, for now, structure engineering of COFs from multi-scale aspects has been conducted to enable optimal overall electrochemical performance in terms of structure durability, electrical conductivity, redox activity, and charge storage. In this review, we give a fundamental and insightful study on the correlations between multi-scale structure engineering and eventual electrochemical properties of COFs, started with introducing their basic chemistries and charge storage principles. The careful discussion on the significant achievements in structure engineering of COFs from linkages, redox sites, polygon skeleton, crystal nanostructures, and composite microstructures, and further their effects on the electrochemical behavior of COFs are presented. Finally, the timely cutting-edge perspectives and in-depth insights into COF-based electrode materials to rationally screen their electrochemical behaviors for addressing future challenges and implementing electrochemical energy storage applications are proposed.

Lithium-ion batteries are widely used in portable electronics and electric vehicles due to their high energy density, stable cycle life, and low self-discharge. However, irreversible lithium loss during the formation of the solid electrolyte interface greatly impairs energy density and cyclability. To compensate for the lithium loss, introducing an external lithium source, that is, a prelithiation agent, is an effective strategy to solve the above problems. Compared with other prelithiation strategies, cathode prelithiation is more cost-effective with simpler operation. Among various cathode prelithiation agents, we first systematically summarize the recent progress of Li₂S-based prelithiation agents, and then propose some novel strategies to tackle the current challenges. This review provides a comprehensive understanding of Li₂S-based prelithiation agents and new research directions in the future.

Great attention has been given to high-performance and inexpensive lithium-ion batteries (LIBs) in response to the ever-increasing demand for the explosive growth of electric vehicles (EVs). High-performance and low-cost Co-free Ni-rich layered cathodes are considered one of the most favorable candidates for next-generation LIBs because the current supply chain of EVs relies heavily on scarce and expensive Co. Herein, we review the recent research progress on Co-free Ni-rich layered cathodes, emphasizing on analyzing the necessity of replacing Co and the popular improvment methods. The current advancements in the design strategies of Co-free Ni-rich layered cathodes are summarized in detail. Despite considerable improvements achieved so far, the main technical challenges contributing to the deterioration of Co-free Ni-rich cathodes such as detrimental phase transitions, crack formation, and severe interfacial side reactions, are difficult to resolve by a single technique. The cooperation of multiple modification strategies is expected to accelerate the industrialization of Co-free Ni-rich layered cathodes, and the corresponding synergistic mechanisms urgently need to be studied. More effects will be aroused to explore high-performance Co-free Ni-rich layered cathodes to promote the sustainable development of LIBs.

Solid-state batteries represent the future of energy storage technology, offering improved safety and energy density. Garnet-type Li₇La₃Zr₂O₁₂ (LLZO) solid-state electrolytes-based solid-state lithium batteries (SSLBs) stand out for their appealing material properties and chemical stability. Yet, their successful deployment depends on conquering interfacial challenges. This review article primarily focuses on the advancement of interfacial engineering for LLZO-based SSLBs. We commence with a concise introduction to solid-state electrolytes and a discussion of the challenges tied to interfacial properties in LLZO-based SSLBs. We deeply explore the correlations between structure and properties and the design principles vital for achieving an ideal electrode/electrolyte interface. Subsequently, we delve into the latest advancements and strategies dedicated to overcoming these challenges, with designated sections on cathode and anode interface design. In the end, we share our insights into the advancements and opportunities for interface design in realizing the full potential of LLZO-based SSLBs, ultimately contributing to the development of safe and high-performance energy storage solutions.

Ruthenium (Ru) has been recognized as a prospective candidate to substitute platinum catalysts in water-splitting-based hydrogen production. However, minimizing the Ru contents, optimizing the water dissociation energy of Ru sites, and enhancing the long-term stability are extremely required, but still face a great challenge. Here, we report on creating tungsten oxide-anchored Ru clusters (Ru–WO_x) with electron-rich and anti-corrosive microenvironments for efficient and robust seawater splitting. Benefiting from the abundant oxygen vacancy structure in tungsten oxide support, the Ru–WO_x exhibits strong Ru–O and Ru–W bonds at the interface. Our study elucidates that the strong Ru–O bonds in Ru–WO_x may accelerate the water dissociation kinetics, and the Ru–W bonds will lead to the strong metal–support interaction and electrons transfer from W to Ru. The optimal Ru–WO_x catalysts exhibit a low overpotential of 29 and 218 mV at the current density of 10 mA cm⁻² in alkaline and seawater media, respectively. The outstanding long-term stability discloses that the Ru–WO_x catalysts own efficient corrosion resistance in seawater electrolysis. We believe that this work offers new insights into the essential roles of electron-rich and anti-corrosive microenvironments in Ru-based catalysts and provide a new pathway to design efficient and robust cathodes for seawater splitting.

Dielectric capacitors with a fast charging/discharging rate, high power density, and long-term stability are essential components in modern electrical devices. However, miniaturizing and integrating capacitors face a persistent challenge in improving their energy density (W_rec) to satisfy the specifications of advanced electronic systems and applications. In this work, leveraging phase-field simulations, we judiciously designed a novel lead-free relaxor ferroelectric material for enhanced energy storage performance, featuring flexible distributed weakly polar endotaxial nanostructures (ENs) embedded within a strongly polar fluctuation matrix. The matrix contributes to substantially enhanced polarization under an external electric field, and the randomly dispersed ENs effectively optimize breakdown phase proportion and provide a strong restoring force, which are advantageous in bolstering breakdown strength and minimizing hysteresis. Remarkably, this relaxor ferroelectric system incorporating ENs achieves an exceptionally high W_rec value of 10.3 J/cm³, accompanied by a large energy storage efficiency (η) of 85.4%. This work introduces a promising avenue for designing new relaxor materials capable of capacitive energy storage with exceptional performance characteristics.

Aluminum–selenium (Al–Se) batteries have been considered as one of the most promising energy storage systems owing to their high capacity, energy density, and cost effectiveness, but Se falls challenges in addressing the shuttle effect of soluble intermediate product and sluggish reaction kinetics in the solid–solid conversion process during cycling. Herein, we propose an unprecedented design concept for fabricating uniform Se/C hollow microspheres with controllable morphologies through low-temperature electro-deoxidation in neutral NaCl–AlCl₃ molten salt system. Such Se/C hollow microspheres are demonstrated to hold a favorable hollow structure for hosting Se, which can not only suppress the dissolution of soluble intermediate products into the electrolyte, thereby maintaining the structural integrity and maximizing Se utilization of the active material, but also promote the electrical/ionic conductivity, thus facilitating the rapid reaction kinetics during cycling. Accordingly, the as-prepared Se/C hollow microspheres exhibit a high reversible capacity of 720.1 mAh g⁻¹ at 500 mA g⁻¹. Even at the high current density of 1000 mA g⁻¹, Se/C delivers a high discharge capacity of 564.0 mAh g⁻¹, long-term stability over 1100 cycles and high Coulombic efficiency of 98.6%. This present work provides valuable insights into short-process recovery of advanced Se-containing materials and value-added utilization for energy storage.

The polymeric gel electrolytes are attractive owing to their higher ionic conductivities than those of dry polymer electrolytes and lowered water activity for enlarged potential window. However, the ionic conductivity and mechanical strength of the Na-ion conducting polymeric gel electrolytes are limited by below 20 mS cm⁻¹ and 2.2 MPa. Herein, we demonstrate Na-ion conducting and flexible polymeric hydrogel electrolytes of the chemically coupled poly(diallyldimethylammonium chloride)-dextrin-N,N′-methylene-bis-acrylamide film immersed in NaClO₄ solution (ex-DDA-Dex + NaClO₄) for flexible sodium-ion hybrid capacitors (f-NIHC). In particular, the anion exchange reaction and synergistic interaction of ex-DDA-Dex with the optimum ClO₄⁻ enable to greatly improve the ionic conductivity up to 27.63 mS cm⁻¹ at 25°C and electrochemical stability window up to 2.6 V, whereas the double networking structure leads to achieve both the mechanical strength (7.48 MPa) and softness of hydrogel electrolytes. Therefore, the f-NIHCs with the ex-DDA-Dex + NaClO₄ achieved high specific and high-rate capacities of 192.04 F g⁻¹ at 500 mA g⁻¹ and 116.06 F g⁻¹ at 10 000 mA g⁻¹, respectively, delivering a large energy density of 120.03 W h kg⁻¹ at 906 W kg⁻¹ and long cyclability of 70% over 500 cycles as well as demonstrating functional operation under mechanical stresses.

The construction of high-efficiency photoanodes is essential for developing outstanding photoelectrochemical (PEC) water splitting cells. Furthermore, insufficient carrier transport capabilities and sluggish surface water oxidation kinetics limit its application. Using a solvothermal annealing strategy, we prepared a nonstoichiometric In–S (NS) group on the surface of an In₂S₃ photoanode in situ and unexpectedly formed a type II transfer path of carrier, thereby reducing the interfacial recombination and promoting the bulk separation. First-principles calculations and comprehensive characterizations demonstrated NS group as an excellent oxygen evolution cocatalyst (OEC) that effectively facilitated carrier transport, lowered the surface overpotential, increased the surface active site, and accelerated the surface oxygen evolution reaction kinetics by precisely altering the rate-determining steps of * to *OH and *O to *OOH. These synergistic effects remarkably enhanced the PEC performance, with a high photocurrent density of 5.02 mA cm⁻² at 1.23 V versus reversible hydrogen electrode and a negative shift in the onset potential by 310 mV. This work provides a new strategy for the in situ preparation of high-efficiency OECs and provides ideas for constructing excellent carrier transfer and transport channels.

Integrating hydrogen evolution reaction (HER) with hydrazine oxidation reaction (HzOR) has an encouraging prospect for the energy-saving hydrogen production, demanding the high-performance bifunctional HER/HzOR electrocatalyst. Ruthenium phosphide/doped carbon composites have exhibited superior activity toward multiple electrocatalytic reactions. To explore the decent water-soluble precursors containing both N and P elements is highly attractive to facilely prepare metal phosphide/doped carbon composites. Herein, as one kind ecofriendly biomolecules, adenine nucleotide was first employed to selectively fabricate the highly pure RuP nanoparticles embedded into porous N,P-codoped carbons (RuP/PNPC) with a straightforward “mix-and-pyrolyze” approach. The newly prepared RuP/PNPC only requires 4.0 and −83.0 mV at 10 mA/cm² separately in alkaline HER and HzOR, outperforming most of reported electrocatalysts, together with the outstanding neutral bifunctional performance. Furthermore, the two-electrode alkaline and neutral overall hydrazine splitting both exhibit significant power-efficiency superiority to the corresponding overall water splitting with the voltage difference of larger than 2 V, which can be also easily driven by the fuel cells and solar cells with considerable H₂ generation. Our report innovates the N- and P-bearing adenine nucleotide to effortlessly synthesize the high-quality RuP/doped carbon composite catalysts, highly potential as a universal platform for metal phosphide-related functional materials.