New Carbon Materials最新文献

Ultra-thin (≤50 μm) lithium metal anodes (LMAs) are highly desirable for high energy density lithium metal batteries (LMBs). However, their fabrication is complicated and costly due to the sticky and brittle nature of metallic Li, and they have a worse cycling stability than their thick counterparts. We report the fabrication of ultra-thin reduced graphene oxide/Li metal (rGO/Li) composite foils with thicknesses ranging from 10 to 50 μm. During the fabrication, disordered rGO sheets and molten metallic Li were stirred and combined at 200 ºC to produce micrometer-thick rGO/Li sheets, which were processed to form an ultra-thin uniform composite foil. The rGO sheets were randomly distributed in the rGO/Li composite to form a three-dimensional network, which is different from the laminated rGO structure previously reported, and supported stable Li plating/stripping behavior. As expected, a superior electrochemical performance was achieved using this composite sheet for the anode. A 50 μm-thick rGO/Li composite foil electrode displayed stable cycling for > 1 600 h at 1 mA cm⁻² and 1 mAh cm⁻² in symmetrical cells in an ether-based electrolyte. A full cell consisting of a 50 μm-thick rGO/Li composite foil anode and a sulfurized polyacrylonitrile cathode had a high capacity retention of 675 mAh g⁻¹ after 220 cycles at 0.2 C.

Compositing lithium metal anodes (LMAs) with carbon-based materials has been given much attention because of the latter's low density, high mechanical strength, stable electrochemical properties, and large specific surface area. Such a composite LMA stands out because of its ability to reduce the volume expansion, lower the local current density, and provide active nucleation sites for uniform Li⁺ plating. Recent research advances in carbon-based materials as scaffolds to make composite anodes are reviewed, including composites with pure metals and their alloys, and compositing strategies to improve anode stability.

A brief overview of recent developments in the formation, detection, and suppression of lithium dendrites in carbon-based lithium-ion batteries is presented. The electrochemical processes that result in the formation of lithium dendrites on the anode surface are reviewed, and various detection methods, including the essential operando technique for understanding the complex mechanism, are then introduced. Methods for suppressing lithium dendrite formation are discussed and prospects for future research and development are presented.

We discuss recent advances in the control and design of carbon hosts/carriers based on their dimensionality (0D, 1D, 2D and 3D) for achieving high performance Li metal anodes. Representative modification strategies for these different carbons for studying their lithium affinity and their influence on the anode performance are highlighted and discussed. Prospects for the design of carbon hosts/carriers for practical rechargeable LMBs are discussed.

To address the issues of non-uniform Li plating/stripping and the large volume fluctuations during their repeated cycling, Li metal anodes, a composite Li anode with a three-dimensional (3D) host has been proposed as a promising strategy to improve the uniformity of Li plating/stripping and relieve volume fluctuations. One key strategy in this area is to develop 3D carbon hosts with gradients of lithiophilicity and conductivity to guide Li deposition from bottom to top, thus maximizing the positive effect of this composite Li anode. Such anodes have recently received significant attention due to the flexibility, adjustability, (electro)chemical stability and light weight of the carbon hosts. This review summarizes recent advances in these anodes, categorizing them into those that have hosts with a lithiophilicity gradient, hosts with a conductivity gradient, and those that have both. Latest research findings are discussed and these different anode categories are reviewed. Prospects for the design of such anodes to promote the use of Li metal anodes in high-energy-density rechargeable batteries are presented.

To solve the problems of large volume changes and the formation of lithium dendrites in lithium metal batteries, the incorporation of carbon into the lithium metal anodes has gained considerable attention due to its excellent chemical and electrochemical stability, as well as its exceptional mechanical strength that allows repeated cycling. This review provides a comprehensive overview of the formation of lithiated graphite (LiC₆) and its role in both bulk and electrode-electrolyte interface regions during lithium plating and stripping. In bulk form, LiC₆ has excellent lithiophilic properties, reducing the overpotential for lithium nucleation and promoting uniform lithium deposition. Additionally, when LiC₆ is introduced at the electrode-electrolyte interfaces, it improves contact between the electrode and electrolyte by acting as a buffering layer, thereby reducing interfacial impedance. Finally, prospects and challenges for the development of Li/C composite anodes are discussed.

Structured carbon-based hosts for the Li anode both improve the transport of Li-ions and reduce the electron transfer rate and have proven to be an effective way to suppress dendrite growth in lithium metal anodes. An in-depth understanding of these effects is needed to clarify the intrinsic electrochemical mechanism involved. We used the finite element method to simulate the two crucial processes controlling Li-ion behavior, electron transfer and Li-ion transport, and visualized the local deposition rate, the overpotential, and the Li-ion concentration in a three-dimensional (3D) Li//electrolyte//Li cell. Our analysis showed a competitive relationship between the rates of Li-ion transport and electron transfer. When the electron transfer rate is relatively slow, there are sufficient Li-ions available near the anode surface and the deposition behavior is controlled by electron transfer. However, when the number of Li-ions is low, Li-ion transport dominates the deposition process because it is unable to keep up with electron transfer, and this causes dendrite formation. Therefore, reducing the reactivity of the Li anode and accelerating Li-ion transport are the two key factors to produce uniform Li metal deposition on the anode, particularly under fast charging conditions and in practical use.

To tackle the issues of rapid electrode degradation and severe safety issues caused by the uncontrollable growth of lithium dendrites in Li metal anodes (LMAs), two-dimensional transition metal carbides/nitrides (MXenes) with a high electrical conductivity, excellent mechanical properties, and abundant surface functional groups have been used as hosts to induce uniform Li nucleation and alleviate the volume changes, eventually inhibiting the formation of Li dendrites. Recent advances in the use of MXene-based nanomaterials in LMAs are summarized. The problems with using LMAs are first considered, and the ways of using MXene-based nanomaterials for suppressing Li dendrite growth and constructing stable LMAs are then summarized. These include the use of MXenes, MXene-metal hybrids, MXene-carbon hybrids, and MXene derivatives as hosts for the anodes and as additives to modify the electrolyte compositions to increase ionic conductivity and inhibit polymer crystallization. Finally, the challenges and prospects for using MXene-based nanomaterials in next-generation LMAs are briefly discussed.

This review highlights several recent models of Li dendrite formation that have been proposed. Based on the comprehensive understanding and insight gained from these models, carbon materials have been developed to prevent the formation of Li dendrites by virtue of their exceptional electrical conductivity, electrochemical stability, mechanical properties and mouldability. A comprehensive review of the advantages of using carbon materials, such as graphene, carbon nanotubes, carbon fibers and hollow carbons, to deal with the formation of Li dendrites in recent years is provided. Finally, the limitations of carbon materials and future research directions for inhibiting Li dendrite formation are summarized as a reference for the development of new carbon materials for high-performance Li metal anodes.

We report the fabrication of vulcanized cross-linked polystyrene grafted on carbon nanotubes (CNTs) for use as an advanced three-dimensional Li host. First, polystyrene was grafted from Br-modified CNTs to form brush-like structure by surface-initiated atom-transfer radical polymerization. Polystyrene grafted on carbon nanotubes was then cross-linked using a Friedel-Crafts reaction and finally vulcanized with sulfur. Vulcanized cross-linked polystyrene grafted on carbon nanotubes was used as a support for the Li metal, and its macro-, meso- and microporous structure increased Li ion transport, buffered the volume changes of the Li anode, and provided a high specific surface area to reduce local current density, which assisted rapid and uniform Li plating/stripping. At the same time, the homogenously distributed sulfur in the support reacted with Li to produce a Li₂S-containing SEI layer, while the CNTs provided conductive pathways for the rapid transmission of electrons. As a result, a Li|Li symmetric cell using this anode material and a Cu current collector had a stable cycling performance of more than 500 h at a current density of 1 mA cm⁻². When LiFePO₄ was used as the cathode, a full cell had a high discharge capacity of 101 mAh g⁻¹ with a capacity retention of 77% after 600 cycles at 1 C.