Graphene with fascinating physicochemical properties has been regarded as one of the most promising candidates to substitute the commercial graphite anode for next-generation lithium-ion batteries (LIBs). [1] As originally suggested by Dahn's group, Li ions can be adsorbed on each side of graphene, forming a Li 2 C 6 stoichiometry with a theoretical specific capacity of 744 mAh g −1 , twice that of graphite (372 mAh g −1 of the first-stage LiC 6 intercalation compound). [2] However, in situ Raman spectroscopy reveals that it is difficult to achieve high Li coverage on graphene because of the low binding energy of Li with carbon and the strong Coulombic repulsion between the adsorbed Li ions. [3] Using density functional theory (DFT) calculations, Lee et al. also found that Li cannot reside on the surface of pristine graphene since its adsorption energy is positive for the entire range of Li content. [4] Therefore, the Li storage capacity of pristine graphene is far from its theoretical value, and is even inferior to that of graphite. Accordingly, it was proposed that defective graphene presents superior Li adsorption because of the increased charge transfer between Li and the defects, and moreover, the specific capacity rises with the increase of defects densities. [5] In the case of the maximum divacancy defect density, the Li storage capacity can reach up to 1675 mAh g −1 . In this regard, reduced graphene oxide (rGO), a form of graphene prepared by a chemical oxidation-exfoliation-reduction process, has been proven to be a potential anode by virtue of its abundant defects and the residual O-containing functional groups. [6] On the other hand, rGO also exhibits the advantages of mass production from the reduction of graphene oxide (GO) with contained costs, which is an essential step for practical applications. [7] As a result, rGO anode is more frequently studied as compared to its pristine graphene counterpart.The groundbreaking work of graphene anodes was reported in 2008 by Honma's group, who demonstrated that the incorporation of carbonaceous materials, i.e., carbon nanotubes (CNTs) and fullerenes (C 60 ), into graphene sheets can efficiently expand the interlayer spacing, thus higher Li storage capacities. [8] Soon Graphene has long been recognized as a potential anode for next-generation lithium-ion batteries (LIBs). The past decade has witnessed the rapid advancement of graphene anodes, and considerable breakthroughs are achieved so far. In this review, the aim is to provide a research roadmap of graphene anodes toward practical LIBs. The Li storage mechanism of graphene is started with and then the approaches to improve its electrochemical performance are comprehensively summarized. First, morphologically engineered graphene anodes with porous, spheric, ribboned, defective and holey structures display improved capacity and rate performance owing to their highly accessible surface area, interconnected diffusion channels, and sufficient active sites. Surface-modified graphene anodes with less aggreg...

Li metal has been recognized as the most promising anode materials for next-generation high-energy-density batteries, however, the inherent issues of dendrite growth and huge volume fluctuations upon Li plating/stripping normally result in fast capacity fading and safety concerns. Functionalized Cu current collectors have so far exhibited significant regulatory effects on stabilizing Li metal anodes (LMAs), and hold a great practical potential owing to their easy fabrication, low-cost and good compatibility with the existing battery technology. In this review, a comprehensive overview of Cu-based current collectors, including planar modified Cu foil, 3D architectured Cu foil and nanostructured 3D Cu substrates, for Li metal batteries is provided. Particularly, the design principles and strategies of functionalized Cu current collectors associated with their functionalities in optimizing Li plating/stripping behaviors are discussed. Finally, the critical issues where there is incomplete understanding and the future research directions of Cu current collectors in practical LMAs are also prospected. This review may shed light on the critical understanding of current collector engineering for high-energy-density Li metal batteries.

Lithium−sulfur (Li−S) batteries are highly attractive for their theoretical energy density and natural abundance, but the drawbacks of low sulfur utilization and rapid capacity fade in high-sulfur-loading cathodes still retard their practical use. To enhance kinetics in high-sulfurloading Li−S cells, it is important to first understand and control the deposition of Li 2 S/Li 2 S from highly soluble lithium polysulfide (LiPS) during discharge processes. Here, we presented a series of multiphasederived self-standing papers with diverse electronic conductivity and LiPS affinity for highly concentrated LiPS discharge processes and explained the Li 2 S/Li 2 S deposition behavior in detail. We demonstrated that high rate capacity and long cycle life of as-assembled paper−LiPS cathodes can be greatly depended on their phase material with high conductivity and LiPS affinity. A high-performance self-standing LiPS host−multiwalled carbon nanotube (MWCNT)/cellulose nanofiber (CNF)/NiCo 2 S 4 (3.5 mg cm −2 ) can catalyze 2.85 mg cm −2 (based on sulfur) loaded LiPS to deliver a high specific capacity of 1154 mAh g −1 at 0.1C and a high rate performance of 963 mAh g −1 at 1C. We suggest that the insulating phase defect of nano-CNF and both highly electronic conductive (above 50 S cm −1 ) and LiPS adsorptive NiCo 2 S 4 can promote the local concentration effect of LiPS, thus contributing to fast and stable heterogeneous particle-shaped deposition of Li 2 S 2 /Li 2 S and leading to high kinetics of the LiPS cathode.

Lithium–sulfur batteries (LSBs) with superior energy density are among the most promising candidates of next‐generation energy storage techniques. As the key step contributing to 75% of the overall capacity, Li2S deposition remains a formidable challenge for LSBs applications because of its sluggish kinetics. The severe kinetic issue originates from the huge interfacial impedances, indicative of the interface‐dominated nature of Li2S deposition. Accordingly, increasing efforts have been devoted to interface engineering for efficient Li2S deposition, which has attained inspiring success to date. However, a systematic overview and in‐depth understanding of this critical field are still absent. In this review, the principles of interface‐controlled Li2S precipitation are presented, clarifying the pivotal roles of electrolyte–substrate and electrolyte–Li2S interfaces in regulating Li2S depositing behavior. For the optimization of the electrolyte–substrate interface, efforts on the design of substrates including metal compounds, functionalized carbons, and organic compounds are systematically summarized. Regarding the regulation of electrolyte–Li2S interface, the progress of applying polysulfides catholytes, redox mediators, and high‐donicity/polarity electrolytes is overviewed in detail. Finally, the challenges and possible solutions aiming at optimizing Li2S deposition are given for further development of practical LSBs. This review would inspire more insightful works and, more importantly, may enlighten other electrochemical areas concerning heterogeneous deposition processes.

Developing host has been recognized a potential countermeasure to circumvent the intrinsic drawbacks of Li metal anode (LMA), such as uncontrolled dendrite growth, unstable solid electrolyte interface, and infinite volume fluctuations. To realize proper Li accommodation, particularly bottom-up deposition of Li metal, gradient designs of host materials including lithiophilicity and/or conductivity have attracted a great deal of attention in recent years. However, a critical and specialized review on this quickly evolving topic is still absent. In this review, we attempt to comprehensively summarize and update the related advances in guiding Li nucleation and deposition. First, the fundamentals regarding Li deposition are discussed, with particular attention to the gradient design principles of host materials. Correspondingly, the progress of creating different gradients in terms of lithiophilicity, conductivity, and their hybrid is systematically reviewed. Finally, future challenges and perspective on the gradient design of advanced hosts towards practical LMAs are provided, which would provide a useful guidance for future studies.