Solid-state lithium metal batteries are facing huge challenges under practical working conditions1,2. Even when the ionic conductivity of composite solid-state electrolytes is increased to 1 mS cm-1, it is still difficult to realize long-life cycling of solid-state batteries above a current density of 1 mA cm-2 and an areal capacity of 1 mAh cm-2 (ref. 3). The fundamental cause is the brittle nature of the solid-electrolyte interphase (SEI) with sluggish lithium-ion transport and the resulting lithium dendrites and severe side reactions. Here we report a ductile inorganic-rich SEI that retains its structural integrity while allowing easy ion diffusion at high current densities and areal capacities. The ductility of the SEI is ascribed to the Ag2S and AgF components, which are formed by a substitution reaction between Li2S/LiF in the SEI and AgNO3 in the dielectric composite electrolytes. Even at a high current density of 15 mA cm-2 and an areal capacity of 15 mAh cm-2, a symmetrical lithium cell with such an SEI has a long cycle life of over 4,500 hours. Furthermore, the ductile SEI also works over 7,000 hours at -30 °C, even under practical conditions of 5 mA cm-2 and 5 mAh cm-2.

ConspectusTwo-dimensional (2D) materials such as graphene and MXenes offer appealing opportunities in electrochemical energy storage due to their large surface area, tunable surface chemistry, and unique electronic properties. One of the primary challenges in utilizing these materials for practical electrodes, especially those with industrial-level thickness, is developing a highly interconnected and porous conductive network. This network is crucial for supporting continuous electron transport, rapid ion diffusion, and effective participation of all active materials in electrochemical reactions. Moreover, the demand for efficient energy storage in advanced electronic devices and electric vehicles has led to the need for not only thicker but also denser electrodes to achieve compact energy storage. Traditional densification methods often compromise between volumetric capacitance and ion-accessible surface area, which can diminish rate performance. As versatile building blocks, 2D materials can overcome these limitations through the assembly into complex superstructures such as 1D fibers, 2D thin films, and 3D porous networks, a capability less attainable by other nanomaterials.This Account explores the pathways from exfoliated 2D nanosheets to densely packed, yet porous assemblies tailored for compact energy storage. Focusing on graphene and MXenes, we delve into the intricate relationships between surface structure, assembly behaviors, and electrochemical performance. We emphasize the crucial role of surface chemistry and interfacial interactions in forming stable colloidal dispersions and subsequent macroscopic structures. Furthermore, we highlight how solvents, acting as spacers, are instrumental in microstructure formation and how capillary force-driven densification is essential for creating compact assemblies. With precise control over shrinkage, the customized dense assemblies can strike a balance between high packing density and sufficient porosity, ensuring efficient ion transport, mechanical stability, and high volumetric performance across various electrochemical energy storage technologies.Furthermore, we highlight the importance of understanding and manipulating the surface chemistry of 2D materials at the atomic level to optimize their assembly and enhance electrochemical behaviors. Advanced in situ characterizations with high temporal and spatial resolution are necessary to gain deeper insights into the complex assembly process. Moreover, the integration of machine learning and computational chemistry emerges as a promising method to predict and design new materials and assembly strategies, potentially accelerating the development of next-generation energy storage systems. Our insights into the assembly and densification of 2D materials provide a comprehensive foundation for future research and practical applications in compact, high-performance energy storage devices. This exploration sets the stage for a transformative approach to overcoming the challenges of current energy storage technologies, promising significant advancements in 2D materials in the field.

Silicon monoxide (SiO) is widely recognized as a promising anode material for next-generation lithium-ion batteries. Owing to its metastable amorphous structure, SiO exhibits a highly complex degree of crystallization at the microscopic level, which significantly influences its electrochemical behavior. As a consequence, accurately regulating the crystallization of SiO, and further establishing the relationship between crystallinity and electrochemical performance are very critical for SiO anodes. In this article, carbon-coated SiO materials with different crystallinity degrees were synthesized using lithium hydroxide monohydrate (LiOH·H2O) as a structural modifier to reveal this rule. Additionally, moderate amount of LiOH·H2O addition results in the forming of an oxygen-rich shell, which effectively inhibits the inward migration of oxygen atoms on the SiO surface and suppresses volume expansion. However, the crystallinity of SiO will gradually enhance and the crystalline phase appears with increasing the amount of LiOH·H2O, which will generate a deteriorative Li+ diffusion kinetic. After balancing the above two contradictions, a mass fraction of 1

An intermediate layer ensuring good thermal dispersion and intimate interfacial contact between the lithium metal anode (LMA) and solid-state electrolyte (SSE) is essential for improving the interfacial stability and suppressing lithium dendrites, endowing solid-state lithium metal batteries with great potential for practical application. Herein, core-shell Cu@Ag nanowires (NWs) with good lithiophilic affinity and thermal conductivity are applied to stabilize the interface between LMA and garnet-type electrolyte. An intimate anodic interface can be achieved with an interfacial resistance of only 14.14 ohm cm(2). The lifetime of Li|Li symmetric cells with the Cu@Ag NWs can be prolonged to 1000 h at 0.5 mA cm(-2). The Li|LiFePO4 full cell delivers a long cycling lifetime over 350 cycles with 90% capacity retention at 1 C. Even with a high-voltage cathode LiNi0.8Co0.1Mn0.1O2, the full cells can still be stably cycled over 240 cycles at 0.5 C, demonstrating the promising potential for practical application.

Photoelectrochemical reaction is emerging as a powerful approach for biomass conversion. However, it has been rarely explored for glucose conversion into value-added chemicals. Here we develop a photoelectrochemical approach for selective oxidation of glucose to high value-added glucaric acid by using single-atom Pt anchored on defective TiO 2 nanorod arrays as photoanode. The defective structure induced by the oxygen vacancies can modulate the charge carrier dynamics and band structure, simultaneously. With optimized oxygen vacancies, the defective TiO 2 photoanode shows greatly improved charge separation and significantly enhanced selectivity and yield of C 6 products. By decorating single-atom Pt on the defective TiO 2 photoanode, selective oxidation of glucose to glucaric acid can be achieved. In this work, defective TiO 2 with single-atom Pt achieves a photocurrent density of 1.91 mA cm −2 for glucose oxidation at 0.6 V versus reversible hydrogen electrode, leading to an 84.3 % yield of glucaric acid under simulated sunlight irradiation.

Protonation has been considered essential for the pseudocapacitive energy storage of polyaniline (PANI) for years, as proton doping in PANI chains not only activates electron transport pathways, but also promotes the proceeding of redox reactions. Rarely has the ability for PANI of storing energy without protonation been investigated, and it remains uncertain whether PANI has pseudocapacitive charge storage properties in an alkaline electrolyte. Here, this work first demonstrates the pseudocapacitive energy storage for PANI without protonation using a PANI/graphene composite as a model material in an alkaline electrolyte. Using in situ Raman spectroscopy coupled with electrochemical quartz crystal microbalance (EQCM) measurements, this work determines the formation of -N= group over potential on a PANI chain and demonstrates the direct contribution of OH- in the nonprotonation type of oxidation reactions. This work finds that the PANI/graphene composite in an alkaline electrolyte has excellent cycling stability with a wider operation voltage of 1 V as well as a slightly higher specific capacitance than that in an acidic electrolyte. The findings provide a new perspective on pseudocapacitive energy storage of PANI-based composites, which will influence the selection of electrolytes for PANI materials and expand their application in energy storage fields.

MXenes have great potential as fast‐charging anodes for sodium storage due to their excellent electrical conductivity, high pseudocapacitive charge storage, and large interlayer distance. The intercalation pseudocapacitance provided by the active sites within the laminate MXene nanosheets is generally the major contributor to their sodium‐storage capacity. Thus, it is highly preferred to construct porous materials with abundant laminate structures to overcome the ion‐diffusion limitation in MXene multilayer films and increase the accessible interlayer sites. Herein, the enhancement of laminate structures in a pre‐assembled Ti3C2Tx network is achieved, under the effects of interlayer slipping of MXene nanosheets during capillary densification, and finally obtained a dense monolith with both high density (2.37 g cm−3) and high porosity (87.3 m2 g−1). This MXene anode material delivers a high capacity of 185 mAh g−1 and a superior rate performance of 55 mAh g−1 (5 A g−1). With improvement of both density and gravimetric capacity, this monolith has a high volumetric capacity of up to 200 mAh cm−3 at 1 A g−1 even after 2000 cycles. Herein, new insights are provided into the design of high‐capacity MXene anodes for sodium‐ion batteries and control of different 2D materials in compact structures.

With a decade of effort, significant progress has been achieved in the synthesis, processing, and applications of MXenes. Metal ions play many crucial roles, such as in MXene delamination, structure regulation, surface modification, MXene composite construction, and even some unique applications. The different roles of metal ions are attributed to their many interactions with MXenes and the unique nature of MXenes, including their layered structure, surface chemistry, and the existence of multi-valent transition metals. Interactions with metal ions are crucial for the energy storage of MXene electrodes, especially in metal ion batteries and supercapacitors with neutral electrolytes. This review aims to provide a good understanding of the interactions between metal ions and MXenes, including the classification and fundamental chemistry of their interactions, in order to achieve their more effective utilization and rational design. It also provides new perspectives on MXene evolution and exfoliation, which may suggest optimized synthesis strategies. In this respect, the different effects of metal ions on MXene synthesis and processing are clarified, and the corresponding mechanisms are elaborated. Research progress on the roles metal ions have in MXene applications is also introduced.

Coating polymer on the surface is an effective way to realize functional modification of the materials for diverse applications, which has been proved to enhance the stability of metal anodes in batteries.However, given the limited operability of coating from polymer dispersions, it is imperative to develop simple aqueous-based strategies from monomers for versatile polymer coating. Herein, a Ti 3 C 2 Tx MXene-assisted approach is proposed to construct polymer coating on zinc metal surfaces directly from the aqueous solution of monomers in an ice bath. By combining a doctor-blading method with spontaneous polymerization of monomers on the substrates at room temperature, a uniform, adhesive, and versatile coating layer assisted by a small amount of MXene is produced in one step. Additionally, MXene nanosheets serve as nanofillers to further enhance the mechanical strength and ionic conductivity of the polymer coating. Benefiting from good film formation and improved interfacial contact, the coated zinc anode exhibits a long cycling lifespan of over 1900 h. The assembled full cells show excellent cycling stability with a high capacity retention of 85.0% at 16 A g -1 over 2600 cycles. This work provides a simple and efficient way to produce polymer coatings directly from monomers, which may give new insights into design multifunctional polymer coatings for various applications.

Carbonaceous materials are the most widely used electrode materials and playing a vital role in electrochemical energy storage devices, due to their abundant resources, excellent conductivity, high chemical stability and tunable microstructure. In this chapter, a simple classification of carbonaceous materials is introduced initially, mainly based on the preparation methods and precursors. Then, the requirements and design principles of carbonaceous electrode materials for different devices, i.e., supercapacitors, lithium-ion batteries, sodium-ion batteries and lithium-sulfur batteries, are clarified in detail. Lastly, some typical carbonaceous materials and related design examples are demonstrated, together with their future perspectives.

Due to outstanding electrical conductivity and excellent solution processing ability, MXenes show great potential as inks for printed/coated electronic devices. To meet the rheological requirements, an ultra-high concentration is usually involved to formulate MXenes into versatile inks, however, low efficiency in rheology regulation, and restacking issues of MXene sheets hinder their further applications. Herein, a gelation-assisted approach is proposed to prepare versatile MXene inks with a 3D interlinked network to well address above issues. With an effective combination of cross-linking as well as the swelling of interlinked network, the gel ink exhibits tunable rheological properties by simply tuning the water amount within the sol-gel system. Among various applicable printing/coating techniques ranging from painting to extrusion printing, blade coating is selected to demonstrate the advantage of MXene gel ink. The smooth coating layer with interlinked 3D structures is greatly beneficial to the uniform and dense zinc deposition with high reversibility, and endows the aqueous zinc ion batteries with a remarkable rate capability. This work provides an alternative approach to prepare versatile MXene inks and would offer MXenes new opportunities for their application in advanced printable electronic devices.

Carbon materials have great potential for being the anode of choice in alkali metal ion batteries and are also crucial for constructing an efficient spatial framework for the production of alloy anodes with higher capacities. For the design of practical carbon anodes, the criteria of sufficient charge storage, a high initial coulombic efficiency, and excellent stability are proposed, which calls for the selection and optimization of the carbon microstructure as well as the matching of electrolytes. For the design of the carbon framework for alloy anodes, the principles of interfacial cohesion, spatial interconnection, and structural stability are proposed, thus recommending a proactive design strategy for better stability and volumetric performance. Research history together with representative research progress is reviewed and discussed in detail in an attempt to stimulate more research interest and promote ideas for the critical search for the right carbon to use as an anode in alkali metal ion batteries. Lastly, specific bottlenecks restricting the successful transfer of these carbons from laboratory to industry are highlighted. The importance of a precise understanding of the charge storage mechanism, the development of matching electrolytes, and the ability to produce the necessary carbon framework in large quantity for higher capacity alloy anodes are discussed.

Great progress has been made in the development of cathode materials for Al-metal batteries. However, the in-depth study of Al anodes, especially the battery instability caused by Al dendrite growth, has not received much attention. In this work, we have identified the in-situ formation of Al dendrite growth, which is proved to bottleneck the practical use of Al-metal batteries. The dendrite formation severely affects battery performance, such as voltage and efficiency fluctuations, unstable cycling, etc. To further demonstrate the detailed growing process of dendrites, we make a comprehensive investigation into the interfacial chemistry of Al anode. We have found that the naturally formed Al2O3 surface film is dissolved in the ionic liquid electrolyte during Al plating, accompanied by the formation of solid-electrolyte interphase containing Al-Cl and Al-O like species on the anode surface before dendrite growth. To suppress this dendrite growth, we propose the use of porous Al, which provides a homogeneous ion flux and decreases the local current density. As a result, the porous anode maintains stable cycling over a wide range of current densities and areal capacities. The Al-graphite battery shows stable cycling up to 18000 times without capacity decay. This work suggests the significance of suppressing dendrite growth for the real applications and commercialization of Al-metal batteries and will draw attention to the battery design from the anode side.

Sulfur is an important electrode material in metal−sulfur batteries. It is usually coupled with metal anodes and undergoes electrochemical reduction to form metal sulfides. Herein, we demonstrate, for the first time, the reversible sulfur oxidation process in AlCl 3 /carbamide ionic liquid, where sulfur is electrochemically oxidized by AlCl 4 − to form AlSCl 7 . The sulfur oxidation is: 1) highly reversible with an efficiency of ~94%; and 2) workable within a wide range of high potentials. As a result, the Al−S battery based on sulfur oxidation can be cycled steadily around ~1.8 V, which is the highest operation voltage in Al−S batteries. The study of sulfur oxidation process benefits the understanding of sulfur chemistry and provides a valuable inspiration for the design of other high-voltage metal−sulfur batteries, not limited to Al−S configurations.

Rechargeable aqueous zinc (Zn) ion-based energy storage systems have been reviving recently because of their low cost and high safety merits; however, they still suffer from the problems of corrosion and dendrite growth on Zn metal anodes that cause gas generation and early battery failure. Unfortunately, the corrosion problem has not received sufficient attention until now. Here, it is pioneeringly demonstrated that decorating the Zn surface with a dual-functional metallic indium (In) layer, acting as both a corrosion inhibitor and a nucleating agent, is a facile but effective strategy to suppress both drastic corrosion and dendrite growth. Symmetric cells assembled with the treated Zn electrodes can sustain up to 1500 h of plating/stripping cycles with an ultralow voltage hysteresis (54 mV), and a 5000 cycle-life is achieved for a prototype full cell. This work will instigate the further development of aqueous metal-based energy storage systems.

Rechargeable aqueous zinc (Zn) ion-based energy storage systems have been reviving recently because of their low cost and high safety merits; however, they still suffer from the problems of corrosion and dendrite growth on Zn metal anodes that cause gas generation and early battery failure. Unfortunately, the corrosion problem has not received sufficient attention until now. Here, it is pioneeringly demonstrated that decorating the Zn surface with a dual-functional metallic indium (In) layer, acting as both a corrosion inhibitor and a nucleating agent, is a facile but effective strategy to suppress both drastic corrosion and dendrite growth. Symmetric cells assembled with the treated Zn electrodes can sustain up to 1500 h of plating/stripping cycles with an ultralow voltage hysteresis (54 mV), and a 5000 cycle-life is achieved for a prototype full cell. This work will instigate the further development of aqueous metal-based energy storage systems.

The serious safety issues caused by uncontrollable lithium (Li) dendrite growth, especially at high current densities, seriously hamper the rapid charging of Li metal‐based batteries. Here, the construction of Al–Li alloy/LiCl‐based Li anode (ALA/Li anode) is reported by displacement and alloying reaction between an AlCl 3 ‐ionic liquid and a Li foil. This layer not only has high ion‐conductivity and good electron resistivity but also much improved mechanical strength (776 MPa) as well as good flexibility compared to a common solid electrolyte interphase layer (585 MPa). The high mechanical strength of the Al–Li alloy interlayer effectively eliminates volume expansion and dendrite growth in Li metal batteries, so that the ALA/Li anode achieves superior cycling for 1600 h (2.0 mA cm −2 ) and 1000 cycles at an ultrahigh current density (20 mA cm −2 ) without dendrite formation in symmetric batteries. In lithium–sulfur batteries, the dense alloy layer prevents direct contact between polysulfides and Li metal, inhibiting the shuttle effect and electrolyte decomposition. Long cycling performance is achieved even at a high current density (4 C) and a low electrolyte/sulfur (6.0 µL mg −1 ). This easy fabrication process provides a strategy to realize reliable safety during the rapid charging of Li‐metal batteries.