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Lithium batteries are key components of portable devices and electric vehicles due to their high energy density and long cycle life. To meet the increasing requirements of electric devices, however, energy density of Li batteries needs to be further improved. Anode materials, as a key component of the Li batteries, have a remarkable effect on the increase of the overall energy density. At present, various anode materials including Li anodes, high‐capacity alloy‐type anode materials, phosphorus‐based anodes, and silicon anodes have shown great potential for Li batteries. Composite‐structure anode materials will be further developed to cater to the growing demands for electrochemical storage devices with high‐energy‐density and high‐power‐density. In this review, the latest progress in the development of high‐energy Li batteries focusing on high‐energy‐capacity anode materials has been summarized in detail. In addition, the challenges for the rational design of current Li battery anodes and the future trends are also presented. The increasing development of battery‐powered vehicles for exceeding 500 km endurance has stimulated the exploration of lithium‐ion batteries with high‐energy‐density and high‐power‐density. In this review, proximate developments in various types of high specific energy lithium‐ion batteries are screened, focusing on silicon‐based anode, phosphorus‐based anode, lithium metal anode, and hybrid anode systems.

The recycling and treatment of wastewater using microbial fuel cells (MFCs) has been attracting significant attention as a way to control energy crises and water pollution simultaneously. Despite all efforts, MFCs are unable to produce high energy or efficiently treat pollutants due to several issues, one being the anode’s material. The anode is one of the most important parts of an MFC. Recently, different types of anode materials have been developed to improve the removal rate of pollutants and the efficiency of energy production. In MFCs, carbon-based materials have been employed as the most commonly preferred anode material. An extensive range of potentials are presently available for use in the fabrication of anode materials and can considerably minimize the current challenges, such as the need for high quality materials and their costs. The fabrication of an anode using biomass waste is an ideal approach to address the present issues and increase the working efficiency of MFCs. Furthermore, the current challenges and future perspectives of anode materials are briefly discussed.

HighlightsRepresentative methods for calculating the depth of discharge of different Zn anodes are introduced.Recent advances of aqueous Zn metal batteries with high Zn utilization are reviewed and categorized according to Zn anodes with different structures.The working mechanism of anode-free aqueous Zn metal batteries is introduced in detail, and different modification strategies for anode-free aqueous Zn metal batteries are summarized.Aqueous zinc metal batteries (AZMBs) are promising candidates for next-generation energy storage due to the excellent safety, environmental friendliness, natural abundance, high theoretical specific capacity, and low redox potential of zinc (Zn) metal. However, several issues such as dendrite formation, hydrogen evolution, corrosion, and passivation of Zn metal anodes cause irreversible loss of the active materials. To solve these issues, researchers often use large amounts of excess Zn to ensure a continuous supply of active materials for Zn anodes. This leads to the ultralow utilization of Zn anodes and squanders the high energy density of AZMBs. Herein, the design strategies for AZMBs with high Zn utilization are discussed in depth, from utilizing thinner Zn foils to constructing anode-free structures with theoretical Zn utilization of 100%, which provides comprehensive guidelines for further research. Representative methods for calculating the depth of discharge of Zn anodes with different structures are first summarized. The reasonable modification strategies of Zn foil anodes, current collectors with pre-deposited Zn, and anode-free aqueous Zn metal batteries (AF-AZMBs) to improve Zn utilization are then detailed. In particular, the working mechanism of AF-AZMBs is systematically introduced. Finally, the challenges and perspectives for constructing high-utilization Zn anodes are presented.

A comprehensive understanding of the solid–electrolyte interphase (SEI) composition is crucial to developing high-energy batteries based on lithium metal anodes. A particularly contentious issue concerns the presence of LiH in the SEI. Here we report on the use of synchrotron-based X-ray diffraction and pair distribution function analysis to identify and differentiate two elusive components, LiH and LiF, in the SEI of lithium metal anodes. LiH is identified as a component of the SEI in high abundance, and the possibility of its misidentification as LiF in the literature is discussed. LiF in the SEI is found to have different structural features from LiF in the bulk phase, including a larger lattice parameter and a smaller grain size (<3 nm). These characteristics favour Li + transport and explain why an ionic insulator, like LiF, has been found to be a favoured component for the SEI. Finally, pair distribution function analysis reveals key amorphous components in the SEI. X-ray diffraction and Rietveld refinement analysis confirm the presence of LiH in the solid–electrolyte interphase of lithium metal anodes.

Improving the anode properties, including increasing its capacity, is one of the basic necessities to improve battery performance. In this paper, high-capacity anodes with alloy performance are introduced, then the problem of fragmentation of these anodes and its effect during the cyclic life is stated. Then, the effect of reducing the size to the nanoscale in solving the problem of fragmentation and improving the properties is discussed, and finally the various forms of nanomaterials are examined. In this paper, electrode reduction in the anode, which is a nanoscale phenomenon, is described. The negative effects of this phenomenon on alloy anodes are expressed and how to eliminate these negative effects by preparing suitable nanostructures will be discussed. Also, the anodes of the titanium oxide family are introduced and the effects of Nano on the performance improvement of these anodes are expressed, and finally, the quasi-capacitive behavior, which is specific to Nano, will be introduced. Finally, the third type of anodes, exchange anodes, is introduced and their function is expressed. The effect of Nano on the reversibility of these anodes is mentioned. The advantages of nanotechnology for these electrodes are described. In this paper, it is found that nanotechnology, in addition to the common effects such as reducing the penetration distance and modulating the stress, also creates other interesting effects in this type of anode, such as capacitive quasi-capacitance, changing storage mechanism and lower volume change.

Silicon (Si)‐based solid‐state batteries (Si‐SSBs) are attracting tremendous attention because of their high energy density and unprecedented safety, making them become promising candidates for next‐generation energy storage systems. Nevertheless, the commercialization of Si‐SSBs is significantly impeded by enormous challenges including large volume variation, severe interfacial problems, elusive fundamental mechanisms, and unsatisfied electrochemical performance. Besides, some unknown electrochemical processes in Si‐based anode, solid‐state electrolytes (SSEs), and Si‐based anode/SSE interfaces are still needed to be explored, while an in‐depth understanding of solid–solid interfacial chemistry is insufficient in Si‐SSBs. This review aims to summarize the current scientific and technological advances and insights into tackling challenges to promote the deployment of Si‐SSBs. First, the differences between various conventional liquid electrolyte‐dominated Si‐based lithium‐ion batteries (LIBs) with Si‐SSBs are discussed. Subsequently, the interfacial mechanical contact model, chemical reaction properties, and charge transfer kinetics (mechanical–chemical kinetics) between Si‐based anode and three different SSEs (inorganic (oxides) SSEs, organic–inorganic composite SSEs, and inorganic (sulfides) SSEs) are systemically reviewed, respectively. Moreover, the progress for promising inorganic (sulfides) SSE‐based Si‐SSBs on the aspects of electrode constitution, three‐dimensional structured electrodes, and external stack pressure is highlighted, respectively. Finally, future research directions and prospects in the development of Si‐SSBs are proposed. This review provides a systematic overview of silicon‐based solid‐state batteries (Si‐SSBs), focusing on the different interfacial configuration characteristics and mechanisms between various types of solid‐state electrolytes and Si‐based anodes as well as the correlations between these interfacial characteristics and electrochemical performance. We envision that this review can point navigation for benefiting the future advancement of Si‐SSBs.

HighlightsA novel hydrogel with high water retention and Zn2+ transference number of 0.604 was constructed by copolymerizing sulfobetaine and acrylamide in Zn(ClO4)2 solution.The designed electrolyte configuration enables in situ generation of the organic–inorganic hybrid interface, which contributes to the electrodeposition uniformity and corrosion resistance of the anode.Zn–Zn and Zn–MnO2 cells based on hydrogel electrolyte exhibit outstanding cycling stability (over 3000 h under 0.5 mA cm−2/0.5 mAh cm−2 after two-time shelving).Aqueous zinc metal batteries are noted for their cost-effectiveness, safety and environmental friendliness. However, the water-induced notorious issues such as continuous electrolyte decomposition and uneven Zn electrochemical deposition remarkably restrict the development of the long-life zinc metal batteries. In this study, zwitterionic sulfobetaine is introduced to copolymerize with acrylamide in zinc perchlorate (Zn(ClO4)2) solution. The designed gel framework with hydrophilic and charged groups can firmly anchor water molecules and construct ion migration channels to accelerate ion transport. The in situ generated hybrid interface, which is composed of the organic functionalized outer layer and inorganic Cl− containing inner layer, can synergically lower the mass transfer overpotential, reduce water-related side reactions and lead to uniform Zn deposition. Such a novel electrolyte configuration enables Zn//Zn cells with an ultra-long cycling life of over 3000 h and a low polarization potential (~ 0.03 V) and Zn//Cu cells with high Coulombic efficiency of 99.18% for 1000 cycles. Full cells matched with MnO2 cathodes delivered laudable cycling stability and impressive shelving ability. Besides, the flexible quasi-solid-state batteries which are equipped with the anti-vandalism ability (such as cutting, hammering and soaking) can successfully power the LED simultaneously. Such a safe, processable and durable hydrogel promises significant application potential for long-life flexible electronic devices.

Hard carbon is regarded as the most promising anode material for sodium-ion (Na-ion) batteries, owing to its advantages of high abundance, low cost, and low operating potential. However, the rate capability and cycle life span of hard carbon anodes are far from satisfactory, severely hindering its industrial applications. Here, we demonstrate that the desolvation process defines the Na-ion diffusion kinetics and the formation of a solid electrolyte interface (SEI). The 3A zeolite molecular sieve film on the hard carbon is proposed to develop a step-by-step desolvation pathway that effectively reduces the high activation energy of the direct desolvation process. Moreover, step-by-step desolvation yields a thin and inorganic-dominated SEI with a lower activation energy for Na⁺ transport. As a result, it contributes to greatly improved power density and cycling stability for both ester and ether electrolytes. When the above insights are applied, the hard carbon anode achieves the longest life span and minimum capacity fading rate at all evaluated current densities. Moreover, with the increase in current densities, an improved plateau capacity ratio is observed. This step-by-step desolvation strategy comprehensively enhances various properties of hard carbon anodes, which provides the possibility of building practical Na-ion batteries with high power density, high energy density, and durability.

Carbonaceous materials, especially with graphite‐layers structure, as anode for potassium‐ion batteries (PIBs), are the footstone for industrialization of PIBs. However, carbonaceous materials with graphite‐layers structure usually suffer from poor cycle life and inferior stability, not to mention freestanding and flexible PIBs. Here, a freestanding and flexible 3D hybrid architecture by introducing carbon dots on the reduced graphene oxide surface (CDs@rGO) is synthesized as high performance PIBs anode. The CDs@rGO paper has efficient electron and ion transfer channels due to its unique structure, thus enhancing reaction kinetics. In addition, the CDs provide abundant defects and oxygen‐containing functional groups, which can improve the electrochemical performance. This freestanding and flexible anode exhibits the high capacity of 310 mAh g−1 at 100 mA g−1, ultra‐long cycle life (840 cycles with a capacity of 244 mAh g−1 at 200 mA g−1), and excellent rate performance (undergo six consecutive currents changing from 100 to 500 mA g−1, high capacity 185 mAh g−1 at 500 mA g−1), outperforming many existing carbonaceous PIB anodes. The results may provide a starting point for high‐performance freestanding and flexible PIBs and promote the rapid development of next‐generation flexible batteries. A freestanding and flexible 3D hybrid architecture by introducing carbon dots on the reduced graphene oxide surface is synthesized as a high‐performance potassium‐ion battery anode. It may provide a starting point for high‐performance freestanding and flexible potassium‐ion battery and promote the rapid development of next‐generation flexible batteries.

Silicon is a promising anode material for lithium-ion and post lithium-ion batteries but suffers from a large volume change upon lithiation and delithiation. The resulting instabilities of bulk and interfacial structures severely hamper performance and obstruct practical use. Stability improvements have been achieved, although at the expense of rate capability. Herein, a protocol is developed which we describe as two-dimensional covalent encapsulation. Two-dimensional, covalently bound silicon-carbon hybrids serve as proof-of-concept of a new material design. Their high reversibility, capacity and rate capability furnish a remarkable level of integrated performances when referred to weight, volume and area. Different from existing strategies, the two-dimensional covalent binding creates a robust and efficient contact between the silicon and electrically conductive media, enabling stable and fast electron, as well as ion, transport from and to silicon. As evidenced by interfacial morphology and chemical composition, this design profoundly changes the interface between silicon and the electrolyte, securing the as-created contact to persist upon cycling. Combined with a simple, facile and scalable manufacturing process, this study opens a new avenue to stabilize silicon without sacrificing other device parameters. The results hold great promise for both further rational improvement and mass production of advanced energy storage materials. Stabilizing silicon without sacrificing other device parameters is essential for practical use in lithium and post lithium battery anodes. Here, the authors show the skin-like two-dimensional covalent encapsulation furnishing a remarkable level of integrated lithium storage performances of silicon.